Programs & Examples On #Python

Python is a dynamic, strongly typed, object-oriented, multipurpose programming language, designed to be quick (to learn, to use, and to understand), and to enforce a clean and uniform syntax. Two similar but incompatible versions of Python are in use (Python 2.7 or 3.x). For version-specific Python questions, please also use the [tag:python-2.7] or [tag:python-3.x] tags. When using a Python variant (i.e Jython, Pypy, etc.) - please also tag the variant.

Reading and writing environment variables in Python?

If you want to pass global variables into new scripts, you can create a python file that is only meant for holding global variables (e.g. When you import this file at the top of the child script, it should have access to all of those variables.

If you are writing to these variables, then that is a different story. That involves concurrency and locking the variables, which I'm not going to get into unless you want.

Pandas "Can only compare identically-labeled DataFrame objects" error

When you compare two DataFrames, you must ensure that the number of records in the first DataFrame matches with the number of records in the second DataFrame. In our example, each of the two DataFrames had 4 records, with 4 products and 4 prices.

If, for example, one of the DataFrames had 5 products, while the other DataFrame had 4 products, and you tried to run the comparison, you would get the following error:

ValueError: Can only compare identically-labeled Series objects

this should work

import pandas as pd
import numpy as np

firstProductSet = {'Product1': ['Computer','Phone','Printer','Desk'],
                   'Price1': [1200,800,200,350]
df1 = pd.DataFrame(firstProductSet,columns= ['Product1', 'Price1'])

secondProductSet = {'Product2': ['Computer','Phone','Printer','Desk'],
                    'Price2': [900,800,300,350]
df2 = pd.DataFrame(secondProductSet,columns= ['Product2', 'Price2'])

df1['Price2'] = df2['Price2'] #add the Price2 column from df2 to df1

df1['pricesMatch?'] = np.where(df1['Price1'] == df2['Price2'], 'True', 'False')  #create new column in df1 to check if prices match
df1['priceDiff?'] = np.where(df1['Price1'] == df2['Price2'], 0, df1['Price1'] - df2['Price2']) #create new column in df1 for price diff 
print (df1)

example from

Multiple try codes in one block

You can use fuckit module.
Wrap your code in a function with @fuckit decorator:

def func():
    code a
    code b #if b fails, it should ignore, and go to c.
    code c #if c fails, go to d
    code d

How to install pip for Python 3 on Mac OS X?

  1. brew install python3
  2. create alias in your shell profile

    • eg. alias pip3="python3 -m pip" in my .zshrc

? ~ pip3 --version

pip 9.0.1 from /usr/local/lib/python3.6/site-packages (python 3.6)

Scikit-learn train_test_split with indices

The docs mention train_test_split is just a convenience function on top of shuffle split.

I just rearranged some of their code to make my own example. Note the actual solution is the middle block of code. The rest is imports, and setup for a runnable example.

from sklearn.model_selection import ShuffleSplit
from sklearn.utils import safe_indexing, indexable
from itertools import chain
import numpy as np
X = np.reshape(np.random.randn(20),(10,2)) # 10 training examples
y = np.random.randint(2, size=10) # 10 labels
seed = 1

cv = ShuffleSplit(random_state=seed, test_size=0.25)
arrays = indexable(X, y)
train, test = next(cv.split(X=X))
iterator = list(chain.from_iterable((
    safe_indexing(a, train),
    safe_indexing(a, test),
    ) for a in arrays)
X_train, X_test, train_is, test_is, y_train, y_test, _, _  = iterator


Now I have the actual indexes: train_is, test_is

What is the purpose of class methods?

Factory methods (alternative constructors) are indeed a classic example of class methods.

Basically, class methods are suitable anytime you would like to have a method which naturally fits into the namespace of the class, but is not associated with a particular instance of the class.

As an example, in the excellent unipath module:

Current directory

  • Path.cwd()
    • Return the actual current directory; e.g., Path("/tmp/my_temp_dir"). This is a class method.
  • .chdir()
    • Make self the current directory.

As the current directory is process wide, the cwd method has no particular instance with which it should be associated. However, changing the cwd to the directory of a given Path instance should indeed be an instance method.

Hmmm... as Path.cwd() does indeed return a Path instance, I guess it could be considered to be a factory method...

Removing character in list of strings

Here's a short one-liner using regular expressions:

print [re.compile(r"8").sub("", m) for m in mylist]

If we separate the regex operations and improve the namings:

pattern = re.compile(r"8") # Create the regular expression to match
res = [pattern.sub("", match) for match in mylist] # Remove match on each element
print res

Concatenate a NumPy array to another NumPy array

I found this link while looking for something slightly different, how to start appending array objects to an empty numpy array, but tried all the solutions on this page to no avail.

Then I found this question and answer: How to add a new row to an empty numpy array

The gist here:

The way to "start" the array that you want is:

arr = np.empty((0,3), int)

Then you can use concatenate to add rows like so:

arr = np.concatenate( ( arr, [[x, y, z]] ) , axis=0)

See also

How to upgrade Python version to 3.7?

On ubuntu you can add this PPA Repository and use it to install python 3.7:

Or a different PPA that provides several Python versions is Deadsnakes:

See also here: (I know it says 3.6 in the url, but the deadsnakes ppa also contains 3.7 so you can use it for 3.7 just the same)

If you want "official" you'd have to install it from the sources from the site, get the code (which you already downloaded) and do this:

tar -xf Python-3.7.0.tar.xz
cd Python-3.7.0
sudo make install        <-- sudo is required.

This might take a while

how does multiplication differ for NumPy Matrix vs Array classes?

The main reason to avoid using the matrix class is that a) it's inherently 2-dimensional, and b) there's additional overhead compared to a "normal" numpy array. If all you're doing is linear algebra, then by all means, feel free to use the matrix class... Personally I find it more trouble than it's worth, though.

For arrays (prior to Python 3.5), use dot instead of matrixmultiply.


import numpy as np
x = np.arange(9).reshape((3,3))
y = np.arange(3)


Or in newer versions of numpy, simply use

Personally, I find it much more readable than the * operator implying matrix multiplication...

For arrays in Python 3.5, use x @ y.

Parse date string and change format

You can install the dateutil library. Its parse function can figure out what format a string is in without having to specify the format like you do with datetime.strptime.

from dateutil.parser import parse
dt = parse('Mon Feb 15 2010')
# datetime.datetime(2010, 2, 15, 0, 0)
# 15/02/2010

Python speed testing - Time Difference - milliseconds

I am not a Python programmer, but I do know how to use Google and here's what I found: you use the "-" operator. To complete your code:

from datetime import datetime

tstart =

# code to speed test

tend =
print tend - tstart

Additionally, it looks like you can use the strftime() function to format the timespan calculation in order to render the time however makes you happy.

2D arrays in Python

>>> a = []

>>> for i in xrange(3):
...     a.append([])
...     for j in xrange(3):
...             a[i].append(i+j)
>>> a
[[0, 1, 2], [1, 2, 3], [2, 3, 4]]

Python Script to convert Image into Byte array

with BytesIO() as output:
    from PIL import Image
    with as img:
        img.convert('RGB').save(output, 'BMP')                
    data = output.getvalue()[14:]

I just use this for add a image to clipboard in windows.

Django 1.7 throws django.core.exceptions.AppRegistryNotReady: Models aren't loaded yet

Another option is that you have a duplicate entry in INSTALLED_APPS. That threw this error for two different apps I tested. Apparently it's not something Django checks for, but then who's silly enough to put the same app in the list twice. Me, that's who.

splitting a string based on tab in the file

You can use regexp to do this:

import re
patt = re.compile("[^\t]+")

s = "a\t\tbcde\t\tef"
['a', 'bcde', 'ef']  

Selecting multiple columns in a Pandas dataframe

One different and easy approach: iterating rows

Using iterows

 df1 = pd.DataFrame() # Creating an empty dataframe
 for index,i in df.iterrows():
    df1.loc[index, 'A'] = df.loc[index, 'A']
    df1.loc[index, 'B'] = df.loc[index, 'B']

Pandas dataframe fillna() only some columns in place

For some odd reason this DID NOT work (using Pandas: '0.25.1')

df[['col1', 'col2']].fillna(value=0, inplace=True)

Another solution:

subset_cols = ['col1','col2']
[df[col].fillna(0, inplace=True) for col in subset_cols]


df = pd.DataFrame(data={'col1':[1,2,np.nan,], 'col2':[1,np.nan,3], 'col3':[np.nan,2,3]})


   col1  col2  col3
0  1.00  1.00   nan
1  2.00   nan  2.00
2   nan  3.00  3.00

Apply list comp. to fillna values:

subset_cols = ['col1','col2']
[df[col].fillna(0, inplace=True) for col in subset_cols]


   col1  col2  col3
0  1.00  1.00   nan
1  2.00  0.00  2.00
2  0.00  3.00  3.00

How to set timeout on python's socket recv method?

As mentioned in previous replies, you can use something like: .settimeout() For example:

import socket

s = socket.socket()

s.settimeout(1) # Sets the socket to timeout after 1 second of no activity

host, port = "somehost", 4444
s.connect((host, port))

s.send("Hello World!\r\n")

    rec = s.recv(100) # try to receive 100 bytes
except socket.timeout: # fail after 1 second of no activity
    print("Didn't receive data! [Timeout]")

I hope this helps!!

Python Loop: List Index Out of Range

When you call for i in a:, you are getting the actual elements, not the indexes. When we reach the last element, that is 3, b.append(a[i+1]-a[i]) looks for a[4], doesn't find one and then fails. Instead, try iterating over the indexes while stopping just short of the last one, like

for i in range(0, len(a)-1): Do something

Your current code won't work yet for the do something part though ;)

Python Progress Bar

You can use tqdm:

from tqdm import tqdm

with tqdm(total=100, desc="Adding Users", bar_format="{l_bar}{bar} [ time left: {remaining} ]") as pbar:
    for i in range(100):

In this example the progress bar is running for 5 minutes and it is shown like that:

Adding Users:   3%|¦¦¦¦¦?                                     [ time left: 04:51 ]                                                                                                        

You can change it and customize it as you like.

Best Python IDE on Linux

I haven't played around with it much but eclipse/pydev feels nice.

Is Python interpreted, or compiled, or both?

Yes, it is both compiled and interpreted language. Then why we generally call it as interpreted language?

see how it is both- compiled and interpreted?

First of all I want to tell that you will like my answer more if you are from the Java world.

In the Java the source code first gets converted to the byte code through javac compiler then directed to the JVM(responsible for generating the native code for execution purpose). Now I want to show you that we call the Java as compiled language because we can see that it really compiles the source code and gives the .class file(nothing but bytecode) through:

javac -------> produces Hello.class file

java Hello -------->Directing bytecode to JVM for execution purpose

The same thing happens with python i.e. first the source code gets converted to the bytecode through the compiler then directed to the PVM(responsible for generating the native code for execution purpose). Now I want to show you that we usually call the Python as an interpreted language because the compilation happens behind the scene and when we run the python code through:

python -------> directly excutes the code and we can see the output provied that code is syntactically correct

@ python it looks like it directly executes but really it first generates the bytecode that is interpreted by the interpreter to produce the native code for the execution purpose.

CPython- Takes the responsibility of both compilation and interpretation.

Look into the below lines if you need more detail:

As I mentioned that CPython compiles the source code but actual compilation happens with the help of cython then interpretation happens with the help of CPython

Now let's talk a little bit about the role of Just-In-Time compiler in Java and Python

In JVM the Java Interpreter exists which interprets the bytecode line by line to get the native machine code for execution purpose but when Java bytecode is executed by an interpreter, the execution will always be slower. So what is the solution? the solution is Just-In-Time compiler which produces the native code which can be executed much more quickly than that could be interpreted. Some JVM vendors use Java Interpreter and some use Just-In-Time compiler. Reference: click here

In python to get around the interpreter to achieve the fast execution use another python implementation(PyPy) instead of CPython. click here for other implementation of python including PyPy.

python, sort descending dataframe with pandas

New syntax (either):

 test = df.sort_values(['one'], ascending=[False])
 test = df.sort_values(['one'], ascending=[0])

TensorFlow not found using pip

Here is my Environment (Windows 10 with NVIDIA GPU). I wanted to install TensorFlow 1.12-gpu and failed multiple times but was able to solve by following the below approach.

This is to help Installing TensorFlow-GPU on Windows 10 Systems


  1. Make sure you have NVIDIA graphic card

a. Go to windows explorer, open device manager-->check “Display Adaptors”-->it will show (ex. NVIDIA GeForce) if you have GPU else it will show “HD Graphics”

b. If the GPU is AMD’s then tensorflow doesn’t support AMD’s GPU

  1. If you have a GPU, check whether the GPU supports CUDA features or not.

a. If you find your GPU model at this link, then it supports CUDA.

b. If you don’t have CUDA enabled GPU, then you can install only tensorflow (without gpu)

  1. Tensorflow requires python-64bit version. Uninstall any python dependencies

a. Go to control panel-->search for “Programs and Features”, and search “python”

b. Uninstall things like anaconda and any pythons related plugins. These dependencies might interfere with the tensorflow-GPU installation.

c. Make sure python is uninstalled. Open a command prompt and type “python”, if it throws an error, then your system has no python and your can proceed to freshly install python

  1. Install python freshly

a.TF1.12 supports upto Python 3.6.6. Click here to download Windows x86-64 executable installer

b. While installing, select “Add Python 3.6 to PATH” and then click “Install Now”.

enter image description here

c. After successful installation of python, the installation window provides an option for disabling path length limit which is one of the root-cause of Tensorflow build/Installation issues in Windows 10 environment. Click “Disable path length limit” and follow the instructions to complete the installation.

enter image description here

d. Verify whether python installed correctly. Open a command prompt and type “python”. It should show the version of Python.

enter image description here

  1. Install Visual Studio

Visual Studio 2017 Community

a. Click the "Visual Studio Link" above.Download Visual Studio 2017 Community.

b. Under “Visual Studio IDE” on the left, select “community 2017” and download it

c. During installation, Select “Desktop development with C++” and install

  1. CUDA 9.0 toolkit

a. Click "Link to CUDA 9.0 toolkit" above, download “Base Installer”

b. Install CUDA 9.0

  1. Install cuDNN

a. Click "Link to Install cuDNN" and select “I Agree To the Terms of the cuDNN Software License Agreement”

b. Register for login, check your email to verify email address

c. Click “cuDNN Download” and fill a short survey to reach “cuDNN Download” page

d. Select “ I Agree To the Terms of the cuDNN Software License Agreement”

e. Select “Download cuDNN v7.5.0 (Feb 21, 2019), for CUDA 9.0"

f. In the dropdown, click “cuDNN Library for Windows 10” and download

g. Go to the folder where the file was downloaded, extract the files

enter image description here

h. Add three folders (bin, include, lib) inside the extracted file to environment

enter image description here

i. Type “environment” in windows 10 search bar and locate the “Environment Variables” and click “Path” in “User variable” section and click “Edit” and then select “New” and add those three paths to three “cuda” folders

j. Close the “Environmental Variables” window.

  1. Install tensorflow-gpu

a. Open a command prompt and type “pip install --upgrade tensorflow-gpu”

b. It will install tensorflow-gpu

  1. Check whether it was correctly installed or not

a. Type “python” at the command prompt

b. Type “import tensorflow as tf

c. hello=tf.constant(‘Hello World!’)

d. sess=tf.Session()

e. print( -->Hello World!

  1. Test whether tensorflow is using GPU

a. from tensorflow.python.client import device_lib print(device_lib.list_local_devices())

b. print(device_lib.list_local_devices())

Print "\n" or newline characters as part of the output on terminal

Another suggestion is to do that way:

string = "abcd\n"

But be aware that the print function actually print to the terminal the "\n", your terminal interpret that as a newline, that's it. So, my solution just change the newline in \ + n

How to convert JSON data into a Python object

There are multiple viable answers already, but there are some minor libraries made by individuals that can do the trick for most users.

An example would be json2object. Given a defined class, it deserialises json data to your custom model, including custom attributes and child objects.

Its use is very simple. An example from the library wiki:

from json2object import jsontoobject as jo

class Student:
    def __init__(self):
        self.firstName = None
        self.lastName = None = [Course('')]

class Course:
    def __init__(self, name): = name

data = '''{
"firstName": "James",
"lastName": "Bond",
"courses": [{
    "name": "Fighting"},
    "name": "Shooting"}

model = Student()
result = jo.deserialize(data, model)

programming a servo thru a barometer

You could define a mapping of air pressure to servo angle, for example:

def calc_angle(pressure, min_p=1000, max_p=1200):     return 360 * ((pressure - min_p) / float(max_p - min_p))  angle = calc_angle(pressure) 

This will linearly convert pressure values between min_p and max_p to angles between 0 and 360 (you could include min_a and max_a to constrain the angle, too).

To pick a data structure, I wouldn't use a list but you could look up values in a dictionary:

d = {1000:0, 1001: 1.8, ...}  angle = d[pressure] 

but this would be rather time-consuming to type out!

Load CSV data into MySQL in Python

I think you have to do mydb.commit() all the insert into.

Something like this

import csv
import MySQLdb

mydb = MySQLdb.connect(host='localhost',
cursor = mydb.cursor()

csv_data = csv.reader(file('students.csv'))
for row in csv_data:

    cursor.execute('INSERT INTO testcsv(names, \
          classes, mark )' \
          'VALUES("%s", "%s", "%s")', 
#close the connection to the database.
print "Done"

How do I convert two lists into a dictionary?

If you are working with more than 1 set of values and wish to have a list of dicts you can use this:

def as_dict_list(data: list, columns: list):
    return [dict((zip(columns, row))) for row in data]

Real-life example would be a list of tuples from a db query paired to a tuple of columns from the same query. Other answers only provided for 1 to 1.

Python Git Module experiences?

I thought I would answer my own question, since I'm taking a different path than suggested in the answers. Nonetheless, thanks to those who answered.

First, a brief synopsis of my experiences with GitPython, PyGit, and Dulwich:

  • GitPython: After downloading, I got this imported and the appropriate object initialized. However, trying to do what was suggested in the tutorial led to errors. Lacking more documentation, I turned elsewhere.
  • PyGit: This would not even import, and I could find no documentation.
  • Dulwich: Seems to be the most promising (at least for what I wanted and saw). I made some progress with it, more than with GitPython, since its egg comes with Python source. However, after a while, I decided it may just be easier to try what I did.

Also, StGit looks interesting, but I would need the functionality extracted into a separate module and do not want wait for that to happen right now.

In (much) less time than I spent trying to get the three modules above working, I managed to get git commands working via the subprocess module, e.g.

def gitAdd(fileName, repoDir):
    cmd = ['git', 'add', fileName]
    p = subprocess.Popen(cmd, cwd=repoDir)

gitAdd('exampleFile.txt', '/usr/local/example_git_repo_dir')

This isn't fully incorporated into my program yet, but I'm not anticipating a problem, except maybe speed (since I'll be processing hundreds or even thousands of files at times).

Maybe I just didn't have the patience to get things going with Dulwich or GitPython. That said, I'm hopeful the modules will get more development and be more useful soon.

ImportError: no module named win32api

After installing pywin32

Steps to correctly install your module (pywin32)

  1. First search where is your python pip is present

    1a. For Example in my case location of pip - C:\Users\username\AppData\Local\Programs\Python\Python36-32\Scripts

  2. Then open your command prompt and change directory to your pip folder location.

    cd C:\Users\username\AppData\Local\Programs\Python\Python36-32\Scripts
    C:\Users\username\AppData\Local\Programs\Python\Python36-32\Scripts>pip install 

Restart your IDE

All done now you can use the module .

What's the difference between "2*2" and "2**2" in Python?

  2**2 means 2 squared (2^2)
  2*2 mean 2 times 2 (2x2)

In this case they happen to have the same value, but...

  3**3*4 != 3*3*4

Purpose of __repr__ method?

The __repr__ method simply tells Python how to print objects of a class

Get pandas.read_csv to read empty values as empty string instead of nan

I was still confused after reading the other answers and comments. But the answer now seems simpler, so here you go.

Since Pandas version 0.9 (from 2012), you can read your csv with empty cells interpreted as empty strings by simply setting keep_default_na=False:

pd.read_csv('test.csv', keep_default_na=False)

This issue is more clearly explained in

That was fixed on on Aug 19, 2012 for Pandas version 0.9 in

install cx_oracle for python

The alternate way, that doesn't require RPMs. You need to be root.

  1. Dependencies

    Install the following packages:

    apt-get install python-dev build-essential libaio1
  2. Download Instant Client for Linux x86-64

    Download the following files from Oracle's download site:

    files preview

  3. Extract the zip files

    Unzip the downloaded zip files to some directory, I'm using:

  4. Add environment variables

    Create a file in /etc/profile.d/ that includes

    export ORACLE_HOME=/opt/ora/instantclient_11_2

    Create a file in /etc/ that includes


    Execute the following command

    sudo ldconfig

    Note: you may need to reboot to apply settings

  5. Create a symlink

    cd $ORACLE_HOME 
    ln -s
  6. Install cx_Oracle python package

    • You may install using pip

      pip install cx_Oracle
    • Or install manually

      Download the cx_Oracle source zip that corresponds with your Python and Oracle version. Then expand the archive, and run from the extracted directory:

      python build 
      python install

Converting an OpenCV Image to Black and White

Pay attention, if you use cv.CV_THRESH_BINARY means every pixel greater than threshold becomes the maxValue (in your case 255), otherwise the value is 0. Obviously if your threshold is 0 everything becomes white (maxValue = 255) and if the value is 255 everything becomes black (i.e. 0).

If you don't want to work out a threshold, you can use the Otsu's method. But this algorithm only works with 8bit images in the implementation of OpenCV. If your image is 8bit use the algorithm like this:

cv.Threshold(im_gray_mat, im_bw_mat, threshold, 255, cv.CV_THRESH_BINARY | cv.CV_THRESH_OTSU);

No matter the value of threshold if you have a 8bit image.

TypeError: Image data can not convert to float

I guess you may have this problem in Pycharm. If so, you may try this to your problem.

Go to File-Setting-Tools-Python Scientificin Pycharm and remove the option of Show plots in tool window.

How do you UDP multicast in Python?

This example doesn't work for me, for an obscure reason.

Not obscure, it's simple routing.

On OpenBSD

route add -inet

You can set the route to a dev on Linux

route add -net netmask dev wlp2s0

force all multicast traffic to one interface on Linux

   ifconfig wlp2s0 allmulti

tcpdump is super simple

tcpdump -n multicast

In your code you have:

while True:
  # For Python 3, change next line to "print(sock.recv(10240))"

Why 10240?

multicast packet size should be 1316 bytes

Get year, month or day from numpy datetime64

There's no direct way to do it yet, unfortunately, but there are a couple indirect ways:

[dt.year for dt in dates.astype(object)]


[datetime.datetime.strptime(repr(d), "%Y-%m-%d %H:%M:%S").year for d in dates]

both inspired by the examples here.

Both of these work for me on Numpy 1.6.1. You may need to be a bit more careful with the second one, since the repr() for the datetime64 might have a fraction part after a decimal point.

Pip freeze vs. pip list

pip list

List installed packages: show ALL installed packages that even pip installed implictly

pip freeze

List installed packages: - list of packages that are installed using pip command

pip freeze has --all flag to show all the packages.

Other difference is the output it renders, that you can check by running the commands.

Why can't I use a list as a dict key in python?

The simple answer to your question is that the class list does not implement the method hash which is required for any object which wishes to be used as a key in a dictionary. However the reason why hash is not implemented the same way it is in say the tuple class (based on the content of the container) is because a list is mutable so editing the list would require the hash to be recalculated which may mean the list in now located in the wrong bucket within the underling hash table. Note that since you cannot modify a tuple (immutable) it doesn't run into this problem.

As a side note, the actual implementation of the dictobjects lookup is based on Algorithm D from Knuth Vol. 3, Sec. 6.4. If you have that book available to you it might be a worthwhile read, in addition if you're really, really interested you may like to take a peek at the developer comments on the actual implementation of dictobject here. It goes into great detail as to exactly how it works. There is also a python lecture on the implementation of dictionaries which you may be interested in. They go through the definition of a key and what a hash is in the first few minutes.

How to pass a list from Python, by Jinja2 to JavaScript

To pass some context data to javascript code, you have to serialize it in a way it will be "understood" by javascript (namely JSON). You also need to mark it as safe using the safe Jinja filter, to prevent your data from being htmlescaped.

You can achieve this by doing something like that:

The view

import json

def my_view():
    data = [1, 'foo']
    return render_template('index.html', data=json.dumps(data))

The template

<script type="text/javascript">
    function test_func(data) {
    test_func({{ data|safe }})

Edit - exact answer

So, to achieve exactly what you want (loop over a list of items, and pass them to a javascript function), you'd need to serialize every item in your list separately. Your code would then look like this:

The view

import json

def my_view():
    data = [1, "foo"]
    return render_template('index.html', data=map(json.dumps, data))

The template

{% for item in data %}
    <span onclick=someFunction({{ item|safe }});>{{ item }}</span>
{% endfor %}

Edit 2

In my example, I use Flask, I don't know what framework you're using, but you got the idea, you just have to make it fit the framework you use.

Edit 3 (Security warning)


Otherwise, you would expose your application to XSS vulnerabilities!

Securely storing passwords for use in python script

the secure way is encrypt your sensitive data by AES and the encryption key is derivation by password-based key derivation function (PBE), the master password used to encrypt/decrypt the encrypt key for AES.

master password -> secure key-> encrypt data by the key

You can use pbkdf2

from PBKDF2 import PBKDF2
from Crypto.Cipher import AES
import os
salt = os.urandom(8)    # 64-bit salt
key = PBKDF2("This passphrase is a secret.", salt).read(32) # 256-bit key
iv = os.urandom(16)     # 128-bit IV
cipher =, AES.MODE_CBC, iv)

make sure to store the salt/iv/passphrase , and decrypt using same salt/iv/passphase

Weblogic used similar approach to protect passwords in config files

How can I loop over entries in JSON?

Try this :

import urllib, urllib2, json
url = ''
request = urllib2.Request(url)
request.add_header('User-Agent','Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)')
response = urllib2.urlopen(request)
json_object = json.load(response)
#print json_object['results']
if json_object['team'] == []:
    print 'No Data!'
    for rows in json_object['team']:
        print 'Team ID:' + rows['team_id']
        print 'Team Name:' + rows['team_name']
        print 'Team URL:' + rows['team_icon_url']

Using Python's list index() method on a list of tuples or objects?

I guess the following is not the best way to do it (speed and elegance concerns) but well, it could help :

from collections import OrderedDict as od
t = [('pineapple', 5), ('cherry', 7), ('kumquat', 3), ('plum', 11)]
# bonus :

list of tuples with 2 members can be converted to ordered dict directly, data structures are actually the same, so we can use dict method on the fly.

In Python, how do I create a string of n characters in one line of code?

if you just want any letters:

 'a'*10  # gives 'aaaaaaaaaa'

if you want consecutive letters (up to 26):

 ''.join(['%c' % x for x in range(97, 97+10)])  # gives 'abcdefghij'

What exactly do "u" and "r" string flags do, and what are raw string literals?

Let me explain it simply: In python 2, you can store string in 2 different types.

The first one is ASCII which is str type in python, it uses 1 byte of memory. (256 characters, will store mostly English alphabets and simple symbols)

The 2nd type is UNICODE which is unicode type in python. Unicode stores all types of languages.

By default, python will prefer str type but if you want to store string in unicode type you can put u in front of the text like u'text' or you can do this by calling unicode('text')

So u is just a short way to call a function to cast str to unicode. That's it!

Now the r part, you put it in front of the text to tell the computer that the text is raw text, backslash should not be an escaping character. r'\n' will not create a new line character. It's just plain text containing 2 characters.

If you want to convert str to unicode and also put raw text in there, use ur because ru will raise an error.

NOW, the important part:

You cannot store one backslash by using r, it's the only exception. So this code will produce error: r'\'

To store a backslash (only one) you need to use '\\'

If you want to store more than 1 characters you can still use r like r'\\' will produce 2 backslashes as you expected.

I don't know the reason why r doesn't work with one backslash storage but the reason isn't described by anyone yet. I hope that it is a bug.

Is there a Python Library that contains a list of all the ascii characters?

Since ASCII printable characters are a pretty small list (bytes with values between 32 and 127), it's easy enough to generate when you need:

>>> for c in (chr(i) for i in range(32,127)):
...     print c

... # a few lines removed :)

Drop rows with all zeros in pandas data frame

import pandas as pd

df = pd.DataFrame({'a' : [0,0,1], 'b' : [0,0,-1]})

temp = df.abs().sum(axis=1) == 0      
df = df.drop(temp)


>>> df
   a  b
2  1 -1

Plotting multiple lines, in different colors, with pandas dataframe

You could use groupby to split the DataFrame into subgroups according to the color:

for key, grp in df.groupby(['color']):

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

df = pd.read_table('data', sep='\s+')
fig, ax = plt.subplots()

for key, grp in df.groupby(['color']):
    ax = grp.plot(ax=ax, kind='line', x='x', y='y', c=key, label=key)


yields enter image description here

How to read a CSV file from a URL with Python?

This question is tagged python-2.x so it didn't seem right to tamper with the original question, or the accepted answer. However, Python 2 is now unsupported, and this question still has good google juice for "python csv urllib", so here's an updated Python 3 solution.

It's now necessary to decode urlopen's response (in bytes) into a valid local encoding, so the accepted answer has to be modified slightly:

import csv, urllib.request

url = ''
response = urllib.request.urlopen(url)
lines = [l.decode('utf-8') for l in response.readlines()]
cr = csv.reader(lines)

for row in cr:

Note the extra line beginning with lines =, the fact that urlopen is now in the urllib.request module, and print of course requires parentheses.

It's hardly advertised, but yes, csv.reader can read from a list of strings.

And since someone else mentioned pandas, here's a one-liner to display the CSV in a console-friendly output:

python3 -c 'import pandas
df = pandas.read_csv("")

(Yes, it's three lines, but you can copy-paste it as one command. ;)

TypeError: a bytes-like object is required, not 'str' in python and CSV

I had the same issue with Python3. My code was writing into io.BytesIO().

Replacing with io.StringIO() solved.

How to convert comma-delimited string to list in Python?

Consider the following in order to handle the case of an empty string:

>>> my_string = 'A,B,C,D,E'
>>> my_string.split(",") if my_string else []
['A', 'B', 'C', 'D', 'E']
>>> my_string = ""
>>> my_string.split(",") if my_string else []

Python: How to remove empty lists from a list?

Calling filter with None will filter out all falsey values from the list (which an empty list is)

list2 = filter(None, list1)

Wait until page is loaded with Selenium WebDriver for Python

Have you tried driver.implicitly_wait. It is like a setting for the driver, so you only call it once in the session and it basically tells the driver to wait the given amount of time until each command can be executed.

driver = webdriver.Chrome()

So if you set a wait time of 10 seconds it will execute the command as soon as possible, waiting 10 seconds before it gives up. I've used this in similar scroll-down scenarios so I don't see why it wouldn't work in your case. Hope this is helpful.

To be able to fix this answer, I have to add new text. Be sure to use a lower case 'w' in implicitly_wait.

Can I run Keras model on gpu?

Of course. if you are running on Tensorflow or CNTk backends, your code will run on your GPU devices defaultly.But if Theano backends, you can use following

Theano flags:

"THEANO_FLAGS=device=gpu,floatX=float32 python"

How to read file with space separated values in pandas

If you can't get text parsing to work using the accepted answer (e.g if your text file contains non uniform rows) then it's worth trying with Python's csv library - here's an example using a user defined Dialect:

 import csv

 csv.register_dialect('skip_space', skipinitialspace=True)
 with open(my_file, 'r') as f:
      reader=csv.reader(f , delimiter=' ', dialect='skip_space')
      for item in reader:

How to print float to n decimal places including trailing 0s?

Floating point numbers lack precision to accurately represent "1.6" out to that many decimal places. The rounding errors are real. Your number is not actually 1.6.

Check out:

Mean Squared Error in Numpy?

Another alternative to the accepted answer that avoids any issues with matrix multiplication:

 def MSE(Y, YH):
     return np.square(Y - YH).mean()

From the documents for np.square: "Return the element-wise square of the input."

In Matplotlib, what does the argument mean in fig.add_subplot(111)?

My solution is

fig = plt.figure()
fig.add_subplot(1, 2, 1)   #top and bottom left
fig.add_subplot(2, 2, 2)   #top right
fig.add_subplot(2, 2, 4)   #bottom right

2x2 grid with 1 and 3 merge

Saving numpy array to txt file row wise

import numpy as np

a = [1,2,3]    
b = np.array(a).reshape((1,3))    

No module named 'openpyxl' - Python 3.4 - Ubuntu

I had the same problem solved using instead of pip install :

sudo apt-get install python-openpyxl
sudo apt-get install python3-openpyxl

The sudo command also works better for other packages.

urllib2 and json

This is what worked for me:

import json
import requests
url = ''
payload = {'param': '1', 'data': '2', 'field': '4'}
headers = {'content-type': 'application/json'}
r =, data = json.dumps(payload), headers = headers)

How can I check the extension of a file?

Assuming m is a string, you can use endswith:

if m.endswith('.mp3'):
elif m.endswith('.flac'):

To be case-insensitive, and to eliminate a potentially large else-if chain:

m.lower().endswith(('.png', '.jpg', '.jpeg'))

Python check if website exists

from urllib2 import Request, urlopen, HTTPError, URLError

user_agent = 'Mozilla/20.0.1 (compatible; MSIE 5.5; Windows NT)'
headers = { 'User-Agent':user_agent }
link = ""
req = Request(link, headers = headers)
        page_open = urlopen(req)
except HTTPError, e:
        print e.code
except URLError, e:
        print e.reason
        print 'ok'

To answer the comment of unutbu:

Because the default handlers handle redirects (codes in the 300 range), and codes in the 100-299 range indicate success, you will usually only see error codes in the 400-599 range. Source

How can I remove a key from a Python dictionary?

We can delete a key from a Python dictionary by the some of the following approaches.

Using the del keyword; it's almost the same approach like you did though -

 myDict = {'one': 100, 'two': 200, 'three': 300 }
 print(myDict)  # {'one': 100, 'two': 200, 'three': 300}
 if myDict.get('one') : del myDict['one']
 print(myDict)  # {'two': 200, 'three': 300}


We can do like the following:

But one should keep in mind that, in this process actually it won't delete any key from the dictionary rather than making a specific key excluded from that dictionary. In addition, I observed that it returned a dictionary which was not ordered the same as myDict.

myDict = {'one': 100, 'two': 200, 'three': 300, 'four': 400, 'five': 500}
{key:value for key, value in myDict.items() if key != 'one'}

If we run it in the shell, it'll execute something like {'five': 500, 'four': 400, 'three': 300, 'two': 200} - notice that it's not the same ordered as myDict. Again if we try to print myDict, then we can see all keys including which we excluded from the dictionary by this approach. However, we can make a new dictionary by assigning the following statement into a variable:

var = {key:value for key, value in myDict.items() if key != 'one'}

Now if we try to print it, then it'll follow the parent order:

print(var) # {'two': 200, 'three': 300, 'four': 400, 'five': 500}


Using the pop() method.

myDict = {'one': 100, 'two': 200, 'three': 300}

if myDict.get('one') : myDict.pop('one')
print(myDict)  # {'two': 200, 'three': 300}

The difference between del and pop is that, using pop() method, we can actually store the key's value if needed, like the following:

myDict = {'one': 100, 'two': 200, 'three': 300}
if myDict.get('one') : var = myDict.pop('one')
print(myDict) # {'two': 200, 'three': 300}
print(var)    # 100

Fork this gist for future reference, if you find this useful.

Python to open Chrome browser

You can call get() with the path to Chrome. Below is an example - replace chrome_path with the correct path for your platform.

import webbrowser

url = ''

# MacOS
chrome_path = 'open -a /Applications/Google\ %s'

# Windows
# chrome_path = 'C:/Program Files (x86)/Google/Chrome/Application/chrome.exe %s'

# Linux
# chrome_path = '/usr/bin/google-chrome %s'


How to add title to subplots in Matplotlib?

A shorthand answer assuming import matplotlib.pyplot as plt:


as in:


Then there is no need for superfluous variables.

How do I read CSV data into a record array in NumPy?

You can use this code to send CSV file data into an array:

import numpy as np
csv = np.genfromtxt('test.csv', delimiter=",")

How to smooth a curve in the right way?

If you are interested in a "smooth" version of a signal that is periodic (like your example), then a FFT is the right way to go. Take the fourier transform and subtract out the low-contributing frequencies:

import numpy as np
import scipy.fftpack

N = 100
x = np.linspace(0,2*np.pi,N)
y = np.sin(x) + np.random.random(N) * 0.2

w = scipy.fftpack.rfft(y)
f = scipy.fftpack.rfftfreq(N, x[1]-x[0])
spectrum = w**2

cutoff_idx = spectrum < (spectrum.max()/5)
w2 = w.copy()
w2[cutoff_idx] = 0

y2 = scipy.fftpack.irfft(w2)

enter image description here

Even if your signal is not completely periodic, this will do a great job of subtracting out white noise. There a many types of filters to use (high-pass, low-pass, etc...), the appropriate one is dependent on what you are looking for.

Python-equivalent of short-form "if" in C++

My cryptic version...

a = ['123', '456'][b == True]

Python Error: "ValueError: need more than 1 value to unpack"

Probably you didn't provide an argument on the command line. In that case, sys.argv only contains one value, but it would have to have two in order to provide values for both user_name and script.

Efficiently finding the last line in a text file


count = 0

f = open('last_line1','r')

for line in f.readlines():

    line = line.strip()

    count = count + 1

    print line

print count


count1 = 0

h = open('last_line1','r')

for line in h.readlines():

    line = line.strip()

    count1 = count1 + 1

    if count1 == count:

       print line         #-------------------- this is the last line


How to generate all permutations of a list?

Note that this algorithm has an n factorial time complexity, where n is the length of the input list

Print the results on the run:

global result
result = [] 

def permutation(li):
if li == [] or li == None:

if len(li) == 1:
    print result

for i in range(0,len(li)):
    permutation(li[:i] + li[i+1:])




[1, 2, 3]
[1, 3, 2]
[2, 1, 3]
[2, 3, 1]
[3, 1, 2]
[3, 2, 1]

ValueError: could not convert string to float: id

Perhaps your numbers aren't actually numbers, but letters masquerading as numbers?

In my case, the font I was using meant that "l" and "1" looked very similar. I had a string like 'l1919' which I thought was '11919' and that messed things up.

why should I make a copy of a data frame in pandas

Assumed you have data frame as below

     A    B    C    D
4 -1.0 -1.0 -1.0 -1.0
5 -1.0 -1.0 -1.0 -1.0
6 -1.0 -1.0 -1.0 -1.0
6 -1.0 -1.0 -1.0 -1.0

When you would like create another df2 which is identical to df1, without copy

     A    B    C    D
4 -1.0 -1.0 -1.0 -1.0
5 -1.0 -1.0 -1.0 -1.0
6 -1.0 -1.0 -1.0 -1.0
6 -1.0 -1.0 -1.0 -1.0

And would like modify the df2 value only as below


         A    B    C    D
4  changed -1.0 -1.0 -1.0
5       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0

At the same time the df1 is changed as well

         A    B    C    D
4  changed -1.0 -1.0 -1.0
5       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0

Since two df as same object, we can check it by using the id


So they as same object and one change another one will pass the same value as well.

If we add the copy, and now df1 and df2 are considered as different object, if we do the same change to one of them the other will not change.


         A    B    C    D
4  changed -1.0 -1.0 -1.0
5       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0
6       -1 -1.0 -1.0 -1.0

Good to mention, when you subset the original dataframe, it is safe to add the copy as well in order to avoid the SettingWithCopyWarning

How to close a Tkinter window by pressing a Button?

from tkinter import *

window = tk()

def close_window (): 


button = Button ( text = "Good-bye", command = close_window)


Convert a number range to another range, maintaining ratio

Short-cut/simplified proposal

 NewRange/OldRange = Handy multiplicand or HM
 Convert OldValue in OldRange to NewValue in NewRange = 
 (OldValue - OldMin x HM) + NewMin


Is it possible to get an Excel document's row count without loading the entire document into memory?

The solution suggested in this answer has been deprecated, and might no longer work.

Taking a look at the source code of OpenPyXL (IterableWorksheet) I've figured out how to get the column and row count from an iterator worksheet:

wb = load_workbook(path, use_iterators=True)
sheet = wb.worksheets[0]

row_count = sheet.get_highest_row() - 1
column_count = letter_to_index(sheet.get_highest_column()) + 1

IterableWorksheet.get_highest_column returns a string with the column letter that you can see in Excel, e.g. "A", "B", "C" etc. Therefore I've also written a function to translate the column letter to a zero based index:

def letter_to_index(letter):
    """Converts a column letter, e.g. "A", "B", "AA", "BC" etc. to a zero based
    column index.

    A becomes 0, B becomes 1, Z becomes 25, AA becomes 26 etc.

        letter (str): The column index letter.
        The column index as an integer.
    letter = letter.upper()
    result = 0

    for index, char in enumerate(reversed(letter)):
        # Get the ASCII number of the letter and subtract 64 so that A
        # corresponds to 1.
        num = ord(char) - 64

        # Multiply the number with 26 to the power of `index` to get the correct
        # value of the letter based on it's index in the string.
        final_num = (26 ** index) * num

        result += final_num

    # Subtract 1 from the result to make it zero-based before returning.
    return result - 1

I still haven't figured out how to get the column sizes though, so I've decided to use a fixed-width font and automatically scaled columns in my application.

Print a string as hex bytes?

Another answer in two lines that some might find easier to read, and helps with debugging line breaks or other odd characters in a string:

For Python 2.7

for character in string:
    print character, character.encode('hex')

For Python 3.7 (not tested on all releases of 3)

for character in string:
    print(character, character.encode('utf-8').hex())

How to ignore deprecation warnings in Python

Not to beat you up about it but you are being warned that what you are doing will likely stop working when you next upgrade python. Convert to int and be done with it.

BTW. You can also write your own warnings handler. Just assign a function that does nothing. How to redirect python warnings to a custom stream?

Play audio with Python

Take a look at Simpleaudio, which is a relatively recent and lightweight library for this purpose:

> pip install simpleaudio


import simpleaudio as sa

wave_obj = sa.WaveObject.from_wave_file("path/to/file.wav")
play_obj =

Make sure to use uncompressed 16 bit PCM files.

UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 7: ordinal not in range(128)

You need to encode Unicode explicitly before writing to a file, otherwise Python does it for you with the default ASCII codec.

Pick an encoding and stick with it:

f.write(printinfo.encode('utf8') + '\n')

or use to create a file object that'll encode for you as you write to the file:

import io

f =, 'w', encoding='utf8')

You may want to read:

before continuing.

Is there a library function for Root mean square error (RMSE) in python?

from sklearn import metrics
import bumpy as np

Plot inline or a separate window using Matplotlib in Spyder IDE

Go to Tools >> Preferences >> IPython console >> Graphics >> Backend:Inline, change "Inline" to "Automatic", click "OK"

Reset the kernel at the console, and the plot will appear in a separate window

Tensorflow: Using Adam optimizer

I was having a similar problem. (No problems training with GradientDescent optimizer, but error raised when using to Adam Optimizer, or any other optimizer with its own variables)

Changing to an interactive session solved this problem for me.

sess = tf.Session()


sess = tf.InteractiveSession()

How to get pandas.DataFrame columns containing specific dtype

To get the column names from pandas dataframe in python3- Here I am creating a data frame from a fileName.csv file

>>> import pandas as pd
>>> df = pd.read_csv('fileName.csv')
>>> columnNames = list(df.head(0)) 
>>> print(columnNames)

Search for "does-not-contain" on a DataFrame in pandas

I hope the answers are already posted

I am adding the framework to find multiple words and negate those from dataFrame.

Here 'word1','word2','word3','word4' = list of patterns to search

df = DataFrame

column_a = A column name from from DataFrame df

Search_for_These_values = ['word1','word2','word3','word4'] 

pattern = '|'.join(Search_for_These_values)

result = df.loc[~(df['column_a'].str.contains(pattern, case=False)]

How can I show figures separately in matplotlib?

As of November 2020, in order to show one figure at a time, the following works:

import matplotlib.pyplot as plt

f1, ax1 = plt.subplots()
input("Close the figure and press a key to continue")
f2, ax2 = plt.subplots()
input("Close the figure and press a key to continue")

The call to input() prevents the figure from opening and closing immediately.

How can I get the username of the logged-in user in Django?

if you are using the old way of writting views, in the way of Function-Based-Views...

in your view, you are creating a new variable called usuario to save the request.user probably...

but if you returning to the Template a context_instance, passing the value of the Context of the request, you will get the logged user, just by accessing the request.

// In your views file
from django.shortcuts import render_to_response
from django.template import RequestContext
def your_view(request):
    data = {
        'formulario': Formulario()
        # ...
    return render_to_response('your_template.html',
        data, context_instance=RequestContext(request))

// In your template
<form id='formulario' method='POST' action=''>
    <h2>Publica tu tuit, {{ request.user.username.title }} </h2>
    {% csrf_token %}
    {{ formulario.as_p }}
    <p><input type='submit' value='Confirmar' /></p>

Meaning of @classmethod and @staticmethod for beginner?

Rostyslav Dzinko's answer is very appropriate. I thought I could highlight one other reason you should choose @classmethod over @staticmethod when you are creating an additional constructor.

In the example above, Rostyslav used the @classmethod from_string as a Factory to create Date objects from otherwise unacceptable parameters. The same can be done with @staticmethod as is shown in the code below:

class Date:
  def __init__(self, month, day, year):
    self.month = month   = day
    self.year  = year

  def display(self):
    return "{0}-{1}-{2}".format(self.month,, self.year)

  def millenium(month, day):
    return Date(month, day, 2000)

new_year = Date(1, 1, 2013)               # Creates a new Date object
millenium_new_year = Date.millenium(1, 1) # also creates a Date object. 

# Proof:
new_year.display()           # "1-1-2013"
millenium_new_year.display() # "1-1-2000"

isinstance(new_year, Date) # True
isinstance(millenium_new_year, Date) # True

Thus both new_year and millenium_new_year are instances of the Date class.

But, if you observe closely, the Factory process is hard-coded to create Date objects no matter what. What this means is that even if the Date class is subclassed, the subclasses will still create plain Date objects (without any properties of the subclass). See that in the example below:

class DateTime(Date):
  def display(self):
      return "{0}-{1}-{2} - 00:00:00PM".format(self.month,, self.year)

datetime1 = DateTime(10, 10, 1990)
datetime2 = DateTime.millenium(10, 10)

isinstance(datetime1, DateTime) # True
isinstance(datetime2, DateTime) # False

datetime1.display() # returns "10-10-1990 - 00:00:00PM"
datetime2.display() # returns "10-10-2000" because it's not a DateTime object but a Date object. Check the implementation of the millenium method on the Date class for more details.

datetime2 is not an instance of DateTime? WTF? Well, that's because of the @staticmethod decorator used.

In most cases, this is undesired. If what you want is a Factory method that is aware of the class that called it, then @classmethod is what you need.

Rewriting Date.millenium as (that's the only part of the above code that changes):

def millenium(cls, month, day):
    return cls(month, day, 2000)

ensures that the class is not hard-coded but rather learnt. cls can be any subclass. The resulting object will rightly be an instance of cls.
Let's test that out:

datetime1 = DateTime(10, 10, 1990)
datetime2 = DateTime.millenium(10, 10)

isinstance(datetime1, DateTime) # True
isinstance(datetime2, DateTime) # True

datetime1.display() # "10-10-1990 - 00:00:00PM"
datetime2.display() # "10-10-2000 - 00:00:00PM"

The reason is, as you know by now, that @classmethod was used instead of @staticmethod

What's the function like sum() but for multiplication? product()?


In Python 3.8, the prod function was added to the math module. See:

Older info: Python 3.7 and prior

The function you're looking for would be called prod() or product() but Python doesn't have that function. So, you need to write your own (which is easy).

Pronouncement on prod()

Yes, that's right. Guido rejected the idea for a built-in prod() function because he thought it was rarely needed.

Alternative with reduce()

As you suggested, it is not hard to make your own using reduce() and operator.mul():

from functools import reduce  # Required in Python 3
import operator
def prod(iterable):
    return reduce(operator.mul, iterable, 1)

>>> prod(range(1, 5))

Note, in Python 3, the reduce() function was moved to the functools module.

Specific case: Factorials

As a side note, the primary motivating use case for prod() is to compute factorials. We already have support for that in the math module:

>>> import math

>>> math.factorial(10)

Alternative with logarithms

If your data consists of floats, you can compute a product using sum() with exponents and logarithms:

>>> from math import log, exp

>>> data = [1.2, 1.5, 2.5, 0.9, 14.2, 3.8]
>>> exp(sum(map(log, data)))

>>> 1.2 * 1.5 * 2.5 * 0.9 * 14.2 * 3.8

Note, the use of log() requires that all the inputs are positive.

len() of a numpy array in python

You can transpose the array if you want to get the length of the other dimension.

len(np.array([[2,3,1,0], [2,3,1,0], [3,2,1,1]]).T)

Calling Python in PHP

There's also a PHP extension: Pip - Python in PHP, which I've never tried but had it bookmarked for just such an occasion

Error: 'int' object is not subscriptable - Python

x is already integer(x=0) and again you trying to make x again integer and also you gave indexing which is beyound the limit because x already has only one indexing (0) and you are trying to give indexing same as age so thats why you get this error. use this simple code

name1 = input("What's your name? ")
age1 = int(input ("how old are you?" ))
twentyone = str(21-age1)
print("Hi, " +name1+ " you will be 21 in: " + twentyone + " years.")

What is the difference between Python's list methods append and extend?

append(object) - Updates the list by adding an object to the list.

x = [20]
# List passed to the append(object) method is treated as a single object.
x.append([21, 22, 23])
# Hence the resultant list length will be 2
--> [20, [21, 22, 23]]

extend(list) - Essentially concatenates two lists.

x = [20]
# The parameter passed to extend(list) method is treated as a list.
# Eventually it is two lists being concatenated.
x.extend([21, 22, 23])
# Here the resultant list's length is 4
[20, 21, 22, 23]

What is the difference between range and xrange functions in Python 2.X?

The difference decreases for smaller arguments to range(..) / xrange(..):

$ python -m timeit "for i in xrange(10111):" " for k in range(100):" "  pass"
10 loops, best of 3: 59.4 msec per loop

$ python -m timeit "for i in xrange(10111):" " for k in xrange(100):" "  pass"
10 loops, best of 3: 46.9 msec per loop

In this case xrange(100) is only about 20% more efficient.

Simple way to query connected USB devices info in Python?

If you are working on windows, you can use pywin32 (old link: see update below).

I found an example here:

import win32com.client

wmi = win32com.client.GetObject ("winmgmts:")
for usb in wmi.InstancesOf ("Win32_USBHub"):
    print usb.DeviceID

Update Apr 2020:

'pywin32' release versions from 218 and up can be found here at github. Current version 227.

Getting "Could not find function xmlCheckVersion in library libxml2. Is libxml2 installed?" when installing lxml through pip

It is not strange for me that none of the solutions above came up, but I saw how the igd installation removed the new version and installed the old one, for the solution I downloaded this archive:

and changed the recommended version of the new version: 'lxml==4.3.0' in It works!

Concatenate two PySpark dataframes

This should do it for you ...

from pyspark.sql.types import FloatType
from pyspark.sql.functions import randn, rand, lit, coalesce, col
import pyspark.sql.functions as F

df_1 = sqlContext.range(0, 6)
df_2 = sqlContext.range(3, 10)
df_1 ="id", lit("old").alias("source"))
df_2 ="id")
df_3 = df_1.alias("df_1").join(df_2.alias("df_2"), ==, "outer")\
    [coalesce(,"id")] +\
    [col("df_1." + c) for c in df_1.columns if c != "id"])\

[Ljava.lang.Object; cannot be cast to

You need to add query.addEntity(SwitcherServiceSource.class) before calling the .list() on query.

How to normalize a signal to zero mean and unit variance?

To avoid division by zero!

function x = normalize(x, eps)
    % Normalize vector `x` (zero mean, unit variance)

    % default values
    if (~exist('eps', 'var'))
        eps = 1e-6;

    mu = mean(x(:));

    sigma = std(x(:));
    if sigma < eps
        sigma = 1;

    x = (x - mu) / sigma;

allowing only alphabets in text box using java script

From kosare comments, i have create an demo


      <form name="f" onsubmit="return onlyAlphabets()">
         <input type="text" name="nm">
         <div id="notification"></div>
         <input type="submit">


  function onlyAlphabets() {

  var regex = /^[a-zA-Z]*$/;
  if (regex.test(document.f.nm.value)) {

      //document.getElementById("notification").innerHTML = "Watching.. Everything is Alphabet now";
      return true;
  } else {
      document.getElementById("notification").innerHTML = "Alphabets Only";
      return false;


How can I read user input from the console?

Sometime in the future .NET4.6

//for Double
double inputValues = double.Parse(Console.ReadLine());

//for Int
int inputValues = int.Parse(Console.ReadLine());

Bash script prints "Command Not Found" on empty lines

This might be trivial and not related to the OP's question, but I often made this mistaken at the beginning when I was learning scripting

VAR_NAME = $(hostname)
echo "the hostname is ${VAR_NAME}"  

This will produce 'command not found' response. The correct way is to eliminate the spaces


Python: How to pip install opencv2 with specific version 2.4.9?

python -m pip install opencv-python

which will install opencv based on your current python

Hide Button After Click (With Existing Form on Page)

Here is another solution using Jquery I find it a little easier and neater than inline JS sometimes.

    <script src="//"></script>

        /* if you prefer to functionize and use onclick= rather then the .on bind
        function hide_show(){

            $("#chkbtn").on('click',function() {
    .hidden-div {
    <div class="reform">
        <form id="reform" action="action.php" method="post" enctype="multipart/form-data">
        <input type="hidden" name="type" value="" />
                content here...

                <div class="hidden-div" id="hidden-div">

                more content here that is hidden until the button below is clicked...
                <span style="display:block; padding-left:640px; margin-top:10px;"><button id="chkbtn">Check Availability</button></span>

How to style input and submit button with CSS?

Very simple:

<style type="text/css">
background: black; 
background-position: 0px -401px; 
border: solid 1px #000000; 
color: #ffffff;
height: 21px;
margin-top: -1px;
padding-bottom: 2px;
.buttonstyle:hover {background: white;background-position: 0px -501px;color: #000000; }
<input class="buttonstyle" type="submit" name="submit" Value="Add Items"/>

This is working I have tested.

What is the difference between syntax and semantics in programming languages?

Syntax refers to the structure of a language, tracing its etymology to how things are put together.
For example you might require the code to be put together by declaring a type then a name and then a semicolon, to be syntactically correct.

Type token;

On the other hand, the semantics is about meaning. A compiler or interpreter could complain about syntax errors. Your co-workers will complain about semantics.

Spring - applicationContext.xml cannot be opened because it does not exist

I got the same error. I solved it moving the file applicationContext.xmlin a

sub-folder of the srcfolder. e.g:

context = new ClassPathXmlApplicationContext("/com/ejemplo/dao/applicationContext.xml");

git add, commit and push commands in one?

I found this yolo alias to be amazing to even submit a random comment to the commit while I am being lazy. It works really well out of the box, so I just do git yolo and all my changes are pushed automatically.

Check whether a table contains rows or not sql server 2005


            THEN 'empty table'
        ELSE 'not empty table'
        END AS info

How do I get the time difference between two DateTime objects using C#?

You want the TimeSpan struct:

TimeSpan diff = dateTime1 - dateTime2;

A TimeSpan object represents a time interval (duration of time or elapsed time) that is measured as a positive or negative number of days, hours, minutes, seconds, and fractions of a second. The TimeSpan structure can also be used to represent the time of day, but only if the time is unrelated to a particular date.

There are various methods for getting the days, hours, minutes, seconds and milliseconds back from this structure.

If you are just interested in the difference then:

TimeSpan diff = Math.Abs(dateTime1 - dateTime2);

will give you the positive difference between the times regardless of the order.

If you have just got the time component but the times could be split by midnight then you need to add 24 hours to the span to get the actual difference:

TimeSpan diff = dateTime1 - dateTime2;
if (diff < 0)
    diff = diff + TimeSpan.FromDays(1);

Update value of a nested dictionary of varying depth

@FM's answer has the right general idea, i.e. a recursive solution, but somewhat peculiar coding and at least one bug. I'd recommend, instead:

Python 2:

import collections

def update(d, u):
    for k, v in u.iteritems():
        if isinstance(v, collections.Mapping):
            d[k] = update(d.get(k, {}), v)
            d[k] = v
    return d

Python 3:


def update(d, u):
    for k, v in u.items():
        if isinstance(v,
            d[k] = update(d.get(k, {}), v)
            d[k] = v
    return d

The bug shows up when the "update" has a k, v item where v is a dict and k is not originally a key in the dictionary being updated -- @FM's code "skips" this part of the update (because it performs it on an empty new dict which isn't saved or returned anywhere, just lost when the recursive call returns).

My other changes are minor: there is no reason for the if/else construct when .get does the same job faster and cleaner, and isinstance is best applied to abstract base classes (not concrete ones) for generality.

Fling gesture detection on grid layout

You can use the droidQuery library to handle flings, clicks, long clicks, and custom events. The implementation is built on my previous answer below, but droidQuery provides a slick, simple syntax:

//global variables    private boolean isSwiping = false;
private SwipeDetector.Direction swipeDirection = null;
private View v;//must be instantiated before next call.

//swipe-handling code
$.with(v).swipe(new Function() {
    public void invoke($ droidQuery, Object... params) {
        if (params[0] == SwipeDetector.Direction.START)
            isSwiping = true;
        else if (params[0] == SwipeDetector.Direction.STOP) {
            if (isSwiping) {                    isSwiping = false;
                if (swipeDirection != null) {
                    switch(swipeDirection) {
                        case DOWN :                                //TODO: Down swipe complete, so do something
                        case UP :
                            //TODO: Up swipe complete, so do something
                        case LEFT :
                            //TODO: Left swipe complete, so do something
                        case RIGHT :
                            //TODO: Right swipe complete, so do something
                        default :                                break;
                }                }
        else {
            swipeDirection = (SwipeDetector.Direction) params[0];

Original Answer

This answer uses a combination of components from the other answers here. It consists of the SwipeDetector class, which has an inner interface for listening for events. I also provide a RelativeLayout to show how to override a View's onTouch method to allow both swipe events and other detected events (such as clicks or long clicks).


package self.philbrown;

import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;

 * Detect Swipes on a per-view basis. Based on original code by Thomas Fankhauser on,
 * with adaptations by other authors (see link).
 * @author Phil Brown
 * @see <a href="">android-basic-gesture-detection</a>
public class SwipeDetector implements View.OnTouchListener
     * The minimum distance a finger must travel in order to register a swipe event.
    private int minSwipeDistance;

    /** Maintains a reference to the first detected down touch event. */
    private float downX, downY;

    /** Maintains a reference to the first detected up touch event. */
    private float upX, upY;

    /** provides access to size and dimension contants */
    private ViewConfiguration config;

     * provides callbacks to a listener class for various swipe gestures.
    private SwipeListener listener;

    public SwipeDetector(SwipeListener listener)
        this.listener = listener;

     * {@inheritDoc}
    public boolean onTouch(View v, MotionEvent event)
        if (config == null)
                config = ViewConfiguration.get(v.getContext());
                minSwipeDistance = config.getScaledTouchSlop();

        case MotionEvent.ACTION_DOWN:
            downX = event.getX();
            downY = event.getY();
            return true;
        case MotionEvent.ACTION_UP:
            upX = event.getX();
            upY = event.getY();

            float deltaX = downX - upX;
            float deltaY = downY - upY;

            // swipe horizontal?
            if(Math.abs(deltaX) > minSwipeDistance)
                // left or right
                if (deltaX < 0)
                        if (listener != null)
                                return true;
                if (deltaX > 0)
                        if (listener != null)
                                return true;

            // swipe vertical?
            if(Math.abs(deltaY) > minSwipeDistance)
                // top or down
                if (deltaY < 0)
                        if (listener != null)
                                return true;
                if (deltaY > 0)
                        if (listener != null)
                                return true;
        return false;

     * Provides callbacks to a registered listener for swipe events in {@link SwipeDetector}
     * @author Phil Brown
    public interface SwipeListener
        /** Callback for registering a new swipe motion from the bottom of the view toward its top. */
        public void onUpSwipe(View v);
        /** Callback for registering a new swipe motion from the left of the view toward its right. */
        public void onRightSwipe(View v);
        /** Callback for registering a new swipe motion from the right of the view toward its left. */
        public void onLeftSwipe(View v);
        /** Callback for registering a new swipe motion from the top of the view toward its bottom. */
        public void onDownSwipe(View v);

Swipe Interceptor View

package self.philbrown;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.RelativeLayout;

import com.npeinc.module_NPECore.model.SwipeDetector;
import com.npeinc.module_NPECore.model.SwipeDetector.SwipeListener;

 * View subclass used for handling all touches (swipes and others)
 * @author Phil Brown
public class SwipeInterceptorView extends RelativeLayout
    private SwipeDetector swiper = null;

    public void setSwipeListener(SwipeListener listener)
        if (swiper == null)
            swiper = new SwipeDetector(listener);

    public SwipeInterceptorView(Context context) {

    public SwipeInterceptorView(Context context, AttributeSet attrs) {
        super(context, attrs);

    public SwipeInterceptorView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

    public boolean onTouchEvent(MotionEvent e)
        boolean swipe = false, touch = false;
        if (swiper != null)
            swipe = swiper.onTouch(this, e);
        touch = super.onTouchEvent(e);
        return swipe || touch;

Array Size (Length) in C#

In most of the general cases 'Length' and 'Count' are used.


int[] myArray = new int[size];
int noOfElements = myArray.Length;

Typed List Array:

List <int> myArray = new List<int>();
int noOfElements = myArray.Count;

How should strace be used?

strace -tfp PID will monitor the PID process's system calls, thus we can debug/monitor our process/program status.

jQuery, get html of a whole element

You can clone it to get the entire contents, like this:

var html = $("<div />").append($("#div1").clone()).html();

Or make it a plugin, most tend to call this "outerHTML", like this:

jQuery.fn.outerHTML = function() {
  return jQuery('<div />').append(this.eq(0).clone()).html();

Then you can just call:

var html = $("#div1").outerHTML();

How to convert ActiveRecord results into an array of hashes

For current ActiveRecord (4.2.4+) there is a method to_hash on the Result object that returns an array of hashes. You can then map over it and convert to symbolized hashes:

# Get an array of hashes representing the result (column => value):
# => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
      {"id" => 2, "title" => "title_2", "body" => "body_2"},
# => [{:id => 1, :title => "title_1", :body => "body_1"},
      {:id => 2, :title => "title_2", :body => "body_2"},

See the ActiveRecord::Result docs for more info.

How to get the first non-null value in Java?

This situation calls for some preprocessor. Because if you write a function (static method) which picks the first not null value, it evaluates all items. It is problem if some items are method calls (may be time expensive method calls). And this methods are called even if any item before them is not null.

Some function like this

public static <T> T coalesce(T ...items) …

should be used but before compiling into byte code there should be a preprocessor which find usages of this „coalesce function“ and replaces it with construction like

a != null ? a : (b != null ? b : c)

Update 2014-09-02:

Thanks to Java 8 and Lambdas there is possibility to have true coalesce in Java! Including the crucial feature: particular expressions are evaluated only when needed – if earlier one is not null, then following ones are not evaluated (methods are not called, computation or disk/network operations are not done).

I wrote an article about it Java 8: coalesce – hledáme neNULLové hodnoty – (written in Czech, but I hope that code examples are understandable for everyone).

How do you convert a byte array to a hexadecimal string, and vice versa?

There is a simple one-liner solution not yet mentioned that will convert hex strings into byte arrays (we don't care about negative interpretation here as it does not matter):

BigInteger.Parse(str, System.Globalization.NumberStyles.HexNumber).ToByteArray().Reverse().ToArray();

ActiveRecord find and only return selected columns


This method is designed to perform select by a single column as direct SQL query Returns Array with values of the specified column name The values has same data type as column.


Person.pluck(:id) # SELECT FROM people
Person.uniq.pluck(:role) # SELECT DISTINCT role FROM people
Person.where(:confirmed => true).limit(5).pluck(:id)


Its introduced rails 3.2 onwards and accepts only single column. In rails 4, it accepts multiple columns

MongoDB "root" user

While out of the box, MongoDb has no authentication, you can create the equivalent of a root/superuser by using the "any" roles to a specific user to the admin database.

Something like this:

use admin
db.addUser( { user: "<username>",
          pwd: "<password>",
          roles: [ "userAdminAnyDatabase",

] } )

Update for 2.6+

While there is a new root user in 2.6, you may find that it doesn't meet your needs, as it still has a few limitations:

Provides access to the operations and all the resources of the readWriteAnyDatabase, dbAdminAnyDatabase, userAdminAnyDatabase and clusterAdmin roles combined.

root does not include any access to collections that begin with the system. prefix.

Update for 3.0+

Use db.createUser as db.addUser was removed.

Update for 3.0.7+

root no longer has the limitations stated above.

The root has the validate privilege action on system. collections. Previously, root does not include any access to collections that begin with the system. prefix other than system.indexes and system.namespaces.

glob exclude pattern

More generally, to exclude files that don't comply with some shell regexp, you could use module fnmatch:

import fnmatch

file_list = glob('somepath')    
for ind, ii in enumerate(file_list):
    if not fnmatch.fnmatch(ii, 'bash_regexp_with_exclude'):

The above will first generate a list from a given path and next pop out the files that won't satisfy the regular expression with the desired constraint.

How do I correct "Commit Failed. File xxx is out of date. xxx path not found."

I know this is an old post, but this problem still occurs fairly frequently. The simplest way I've found to resolve it is to rename/delete the .svn/all-wcprops file in the affected folder, then run an update and commit.

How to pass values across the pages in without using Session

You can assign it to a hidden field, and retrieve it using

var value= Request.Form["value"]

Two color borders

Outline is good, but only when you want the border all around.

Lets say if you want to make it only on bottom or top you can use


  #border-top {
  border-top: 1px solid  #ccc;
  box-shadow: inset 0 1px 0 #fff;

<p id="border-top">This is my content</p>

And for bottom:


      #border-bottom {
      border-top: 1px solid  #ccc;
      box-shadow: 0 1px 0 #fff;

    <p id="border-bottom">This is my content</p>

Hope that this helps.

How to clear File Input

I have done something like this and it's working for me


Check last modified date of file in C#

Be aware that the function File.GetLastWriteTime does not always work as expected, the values are sometimes not instantaneously updated by the OS. You may get an old Timestamp, even if the file has been modified right before.

The behaviour may vary between OS versions. For example, this unit test worked well every time on my developer machine, but it always fails on our build server.

  public void TestLastModifiedTimeStamps()
     var tempFile = Path.GetTempFileName();
     var lastModified = File.GetLastWriteTime(tempFile);
     using (new FileStream(tempFile, FileMode.Create, FileAccess.Write, FileShare.None))

     Assert.AreNotEqual(lastModified, File.GetLastWriteTime(tempFile));

See File.GetLastWriteTime seems to be returning 'out of date' value

Your options:

a) live with the occasional omissions.

b) Build up an active component realising the observer pattern (eg. a tcp server client structure), communicating the changes directly instead of writing / reading files. Fast and flexible, but another dependency and a possible point of failure (and some work, of course).

c) Ensure the signalling process by replacing the content of a dedicated signal file that other processes regularly read. It´s not that smart as it´s a polling procedure and has a greater overhead than calling File.GetLastWriteTime, but if not checking the content from too many places too often, it will do the work.

/// <summary>
/// type to set signals or check for them using a central file 
/// </summary>
public class FileSignal
    /// <summary>
    /// path to the central file for signal control
    /// </summary>
    public string FilePath { get; private set; }

    /// <summary>
    /// numbers of retries when not able to retrieve (exclusive) file access
    /// </summary>
    public int MaxCollisions { get; private set; }

    /// <summary>
    /// timespan to wait until next try
    /// </summary>
    public TimeSpan SleepOnCollisionInterval { get; private set; }

    /// <summary>
    /// Timestamp of the last signal
    /// </summary>
    public DateTime LastSignal { get; private set; }

    /// <summary>
    /// constructor
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>
    /// <param name="maxCollisions">numbers of retries when not able to retrieve (exclusive) file access</param>
    /// <param name="sleepOnCollisionInterval">timespan to wait until next try </param>
    public FileSignal(string filePath, int maxCollisions, TimeSpan sleepOnCollisionInterval)
        FilePath = filePath;
        MaxCollisions = maxCollisions;
        SleepOnCollisionInterval = sleepOnCollisionInterval;
        LastSignal = GetSignalTimeStamp();

    /// <summary>
    /// constructor using a default value of 50 ms for sleepOnCollisionInterval
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>
    /// <param name="maxCollisions">numbers of retries when not able to retrieve (exclusive) file access</param>        
    public FileSignal(string filePath, int maxCollisions): this (filePath, maxCollisions, TimeSpan.FromMilliseconds(50))

    /// <summary>
    /// constructor using a default value of 50 ms for sleepOnCollisionInterval and a default value of 10 for maxCollisions
    /// </summary>
    /// <param name="filePath">path to the central file for signal control</param>        
    public FileSignal(string filePath) : this(filePath, 10)

    private Stream GetFileStream(FileAccess fileAccess)
        var i = 0;
        while (true)
                return new FileStream(FilePath, FileMode.Create, fileAccess, FileShare.None);
            catch (Exception e)
                if (i >= MaxCollisions)
                    throw e;

    private DateTime GetSignalTimeStamp()
        if (!File.Exists(FilePath))
            return DateTime.MinValue;
        using (var stream = new FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.None))
            if(stream.Length == 0)
                return DateTime.MinValue;
            using (var reader = new BinaryReader(stream))
                return DateTime.FromBinary(reader.ReadInt64());

    /// <summary>
    /// overwrites the existing central file and writes the current time into it.
    /// </summary>
    public void Signal()
        LastSignal = DateTime.Now;
        using (var stream = new FileStream(FilePath, FileMode.Create, FileAccess.Write, FileShare.None))
            using (var writer = new BinaryWriter(stream))

    /// <summary>
    /// returns true if the file signal has changed, otherwise false.
    /// </summary>        
    public bool CheckIfSignalled()
        var signal = GetSignalTimeStamp();
        var signalTimestampChanged = LastSignal != signal;
        LastSignal = signal;
        return signalTimestampChanged;

Some tests for it:

    public void TestSignal()
        var fileSignal = new FileSignal(Path.GetTempFileName());
        var fileSignal2 = new FileSignal(fileSignal.FilePath);
        Assert.AreEqual(fileSignal.LastSignal, fileSignal2.LastSignal);
        Assert.AreNotEqual(fileSignal.LastSignal, fileSignal2.LastSignal);
        Assert.AreEqual(fileSignal.LastSignal, fileSignal2.LastSignal);

Jquery: Checking to see if div contains text, then action

You might want to try the contains selector:

if ($("#field > div.field-item:contains('someText')").length) {

Also, as other mentioned, you must use == or === rather than =.

How to show Snackbar when Activity starts?

A utils function for show snack bar

fun showSnackBar(activity: Activity, message: String, action: String? = null,
    actionListener: View.OnClickListener? = null, duration: Int = Snackbar.LENGTH_SHORT) {
    val snackBar = Snackbar.make(activity.findViewById(, message, duration)
        .setBackgroundColor(Color.parseColor("#CC000000")) // todo update your color
    if (action != null && actionListener!=null) {
        snackBar.setAction(action, actionListener)

Example using in Activity

  showSnackBar(this, "No internet")
  showSnackBar(this, "No internet", duration = Snackbar.LENGTH_LONG)
  showSnackBar(activity, "No internet", "OK", View.OnClickListener { 
       // handle click 

Example using in Fragment

  showSnackBar(getActivity(), "No internet")

Hope it help

Android Split string

     String s = "having Community Portal|Help Desk|Local Embassy|Reference Desk|Site News";
     StringTokenizer st = new StringTokenizer(s, "|");
        String community = st.nextToken();
        String helpDesk = st.nextToken(); 
        String localEmbassy = st.nextToken();
        String referenceDesk = st.nextToken();
        String siteNews = st.nextToken();

Connecting to a network folder with username/password in Powershell

At first glance one really wants to use New-PSDrive supplying it credentials.

> New-PSDrive -Name P -PSProvider FileSystem -Root \\server\share -Credential domain\user


New-PSDrive : Cannot retrieve the dynamic parameters for the cmdlet. Dynamic parameters for NewDrive cannot be retrieved for the 'FileSystem' provider. The provider does not support the use of credentials. Please perform the operation again without specifying credentials.

The documentation states that you can provide a PSCredential object but if you look closer the cmdlet does not support this yet. Maybe in the next version I guess.

Therefore you can either use net use or the WScript.Network object, calling the MapNetworkDrive function:

$net = new-object -ComObject WScript.Network
$net.MapNetworkDrive("u:", "\\server\share", $false, "domain\user", "password")

Edit for New-PSDrive in PowerShell 3.0

Apparently with newer versions of PowerShell, the New-PSDrive cmdlet works to map network shares with credentials!

New-PSDrive -Name P -PSProvider FileSystem -Root \\Server01\Public -Credential user\domain -Persist

make arrayList.toArray() return more specific types

 public static <E> E[] arrayListToTypedArray(List<E> list) {

    if (list == null) {
      return null;
    int noItems = list.size();
    if (noItems == 0) {
      return null;

    E[] listAsTypedArray;
    E typeHelper = list.get(0);

    try {
      Object o = Array.newInstance(typeHelper.getClass(), noItems);
      listAsTypedArray = (E[]) o;
      for (int i = 0; i < noItems; i++) {
        Array.set(listAsTypedArray, i, list.get(i));
    } catch (Exception e) {
      return null;

    return listAsTypedArray;

Twitter Bootstrap button click to toggle expand/collapse text section above button

I wanted an "expand/collapse" container with a plus and minus button to open and close it. This uses the standard bootstrap event and has animation. This is BS3.

enter image description here


<button id="button" type="button" class="btn btn-primary" 
  data-toggle="collapse" data-target="#demo">
  <span class="glyphicon glyphicon-collapse-down"></span> Show

<div id="demo" class="collapse">
  <ol class="list-group">
      <li class="list-group-item">Warrior</li>
      <li class="list-group-item">Adventurer</li>
      <li class="list-group-item">Mage</li>


  $('#demo').on('', function () {
    $('#button').html('<span class="glyphicon glyphicon-collapse-down"></span> Show');
  $('#demo').on('', function () {
    $('#button').html('<span class="glyphicon glyphicon-collapse-up"></span> Hide');


Job for httpd.service failed because the control process exited with error code. See "systemctl status httpd.service" and "journalctl -xe" for details

on command line type journalctl -xe and the results will be

SELinux is preventing /usr/sbin/httpd from name_bind access on the tcp_socket port 83 or 80

This means that the SELinux is running on your machine and you need to disable it. then edit the configuration file by type the following

nano /etc/selinux/config

Then find the line SELINUX=enforce and change to SELINUX=disabled

Then type the following and run the command to start httpd

setenforce 0

Lastly start a server

systemctl start httpd

Formatting floats in a numpy array

You're confusing actual precision and display precision. Decimal rounding cannot be represented exactly in binary. You should try:

> np.set_printoptions(precision=2)
> np.array([5.333333])
array([ 5.33])

PHP - If variable is not empty, echo some html code

Your problem is in your use of the_field(), which is for Advanced Custom Fields, a wordpress plugin.

If you want to use a field in a variable you have to use this: $web = get_field('website');.

Fill SVG path element with a background-image

You can do it by making the background into a pattern:

  <pattern id="img1" patternUnits="userSpaceOnUse" width="100" height="100">
    <image href="wall.jpg" x="0" y="0" width="100" height="100" />

Adjust the width and height according to your image, then reference it from the path like this:

<path d="M5,50
         l0,100 l100,0 l0,-100 l-100,0
         a50,50 0 1 1 -100,0 50,50 0 1 1 100,0
         l50,100 l-100,0 l50,-100
  fill="url(#img1)" />

Working example

How do I see which version of Swift I'm using?

To see the default version of swift installed on your machine then from the command line, type the following :

swift --version

Apple Swift version 4.1.2 (swiftlang-902.0.54 clang-902.0.39.2)

Target: x86_64-apple-darwin17.6.0

This is most likely the version that is included in the app store version of Xcode that you have installed (unless you have changed it).

If you want to determine the actual version of Swift being used by a particular version of Xcode (a beta, for instance) then from the command line, invoke the swift binary within the Xcode bundle and pass it the parameter --version

/Applications/ --version

Apple Swift version 4.2 (swiftlang-1000.0.16.7 clang-1000.10.25.3)

Target: x86_64-apple-darwin17.6.0

How do I change the string representation of a Python class?

The closest equivalent to Java's toString is to implement __str__ for your class. Put this in your class definition:

def __str__(self):
     return "foo"

You may also want to implement __repr__ to aid in debugging.

See here for more information:

file_get_contents behind a proxy?

There's a similar post here: which explains how to do it.

function file_get_contents_proxy($url,$proxy){

    // Create context stream
    $context_array = array('http'=>array('proxy'=>$proxy,'request_fulluri'=>true));
    $context = stream_context_create($context_array);

    // Use context stream with file_get_contents
    $data = file_get_contents($url,false,$context);

    // Return data via proxy
    return $data;


Inline instantiation of a constant List

You'll need to use a static readonly list instead. And if you want the list to be immutable then you might want to consider using ReadOnlyCollection<T> rather than List<T>.

private static readonly ReadOnlyCollection<string> _metrics =
    new ReadOnlyCollection<string>(new[]

public static ReadOnlyCollection<string> Metrics
    get { return _metrics; }

How to put a tooltip on a user-defined function

@will's method is the best. Just add few lines about the details for the people didn't use ExcelDNA before like me.

Download Excel-DNA IntelliSense from

There are two version, one is for 64, check your Excel version. For my case, I'm using 64 version.

Open Excel/Developer/Add-Ins/Browse and select ExcelDna.IntelliSense64.xll.

Insert a new sheet, change name to "IntelliSense", add function description, as

Then enjoy! :)

enter image description here

Why does flexbox stretch my image rather than retaining aspect ratio?

The key attribute is align-self: center:

.container {_x000D_
  display: flex;_x000D_
  flex-direction: column;_x000D_
img {_x000D_
  max-width: 100%;_x000D_
img.align-self {_x000D_
  align-self: center;_x000D_
<div class="container">_x000D_
    <p>Without align-self:</p>_x000D_
    <img src="" />_x000D_
    <p>With align-self:</p>_x000D_
    <img class="align-self" src="" />_x000D_

Fragment onResume() & onPause() is not called on backstack

What i do in child fragment:

public void onDetach() {
   ParentFragment pf = (ParentFragment) this.getParentFragment();

And then override onResume on ParentFragment

How To Set Up GUI On Amazon EC2 Ubuntu server

For LXDE/Lubuntu

1. connect to your instance (local forwarding port 5901)

ssh -L 5901:localhost:5901 -i "xxx.pem" [email protected]

2. Install packages

sudo apt update && sudo apt upgrade
sudo apt-get install xorg lxde vnc4server lubuntu-desktop

3. Create /etc/lightdm/lightdm.conf

sudo nano /etc/lightdm/lightdm.conf

4. Copy and paste the following into the lightdm.conf and save


5. setup vncserver (you will be asked to create a password for the vncserver)

sudo echo "lxpanel & /usr/bin/lxsession -s LXDE &" >> ~/.vnc/xstartup

6. Restart your instance and reconnect

sudo reboot
ssh -L 5901:localhost:5901 -i "xxx.pem" [email protected]

7. Start vncserver

vncserver -geometry 1280x800

8. In your Remote Desktop Client (e.g. Remmina) set Server to localhost:5901 and protocol to VNC

How do I crop an image in Java?

The solution I found most useful for cropping a buffered image uses the getSubImage(x,y,w,h);

My cropping routine ended up looking like this:

  private BufferedImage cropImage(BufferedImage src, Rectangle rect) {
      BufferedImage dest = src.getSubimage(0, 0, rect.width, rect.height);
      return dest; 

Adding an onclicklistener to listview (android)

You are doing

Object o = prestListView.getItemAtPosition(position);
String str=(String)o;//As you are using Default String Adapter

The o that you get back is not a String, but a prestationEco so you get a CCE when doing the (String)o

jQuery.inArray(), how to use it right?

inArray returns the index of the element in the array, not a boolean indicating if the item exists in the array. If the element was not found, -1 will be returned.

So, to check if an item is in the array, use:

if(jQuery.inArray("test", myarray) !== -1)

How to get Spinner selected item value to string?

Try this:

String text = mySpinner.getSelectedItem().toString();

Like this you can get value for different Spinners.

Leaflet - How to find existing markers, and delete markers?

You can also push markers into an array. See code example, this works for me:

/*create array:*/
var marker = new Array();

/*Some Coordinates (here simulating somehow json string)*/
var items = [{"lat":"51.000","lon":"13.000"},{"lat":"52.000","lon":"13.010"},{"lat":"52.000","lon":"13.020"}];

/*pushing items into array each by each and then add markers*/
function itemWrap() {
    var LamMarker = new L.marker([items[i].lat, items[i].lon]);

/*Going through these marker-items again removing them*/
function markerDelAgain() {
for(i=0;i<marker.length;i++) {

How do you obtain a Drawable object from a resource id in android package?

Following a solution for Kotlin programmers (from API 22)

val res = context?.let { ContextCompat.getDrawable(it, }

Uninitialized constant ActiveSupport::Dependencies::Mutex (NameError)

As mentioned this occurs when using RubyGems 1.6.0 with Ruby on Rails version earlier than version 3. My app is using Ruby on Rails 2.3.3 vendored into the /vendor of the project.

No doubt an upgrade of Ruby on Rails to a newer 2.3.X version may also fix this issue. However, this problem prevents you running Rake to unvendor Ruby on Rails and upgrade it.

Adding require 'thread' to the top of environment.rb did not fix the issue for me. Adding require 'thread' to /vendor/rails/activesupport/lib/active_support.rb did fix the problem.

Excel Reference To Current Cell

You could use


How to retrieve inserted id after inserting row in SQLite using Python?

You could use cursor.lastrowid (see "Optional DB API Extensions"):

cursor.execute('''CREATE TABLE foo (id integer primary key autoincrement ,
                                    username varchar(50),
                                    password varchar(50))''')
cursor.execute('INSERT INTO foo (username,password) VALUES (?,?)',
# 1

If two people are inserting at the same time, as long as they are using different cursors, cursor.lastrowid will return the id for the last row that cursor inserted:

cursor.execute('INSERT INTO foo (username,password) VALUES (?,?)',

cursor2.execute('INSERT INTO foo (username,password) VALUES (?,?)',

# 3
# 2

cursor.execute('INSERT INTO foo (id,username,password) VALUES (?,?,?)',
# 100

Note that lastrowid returns None when you insert more than one row at a time with executemany:

cursor.executemany('INSERT INTO foo (username,password) VALUES (?,?)',
# None

Specifying onClick event type with Typescript and React.Konva

As posted in my update above, a potential solution would be to use Declaration Merging as suggested by @Tyler-sebastion. I was able to define two additional interfaces and add the index property on the EventTarget in this way.

interface KonvaTextEventTarget extends EventTarget {
  index: number

interface KonvaMouseEvent extends React.MouseEvent<HTMLElement> {
  target: KonvaTextEventTarget

I then can declare the event as KonvaMouseEvent in my onclick MouseEventHandler function.

onClick={(event: KonvaMouseEvent) => {

I'm still not 100% if this is the best approach as it feels a bit Kludgy and overly verbose just to get past the tslint error.

Convert a string to a double - is this possible?

For arbitrary precision mathematics PHP offers the Binary Calculator which supports numbers of any size and precision, represented as strings.

$s = '1234.13';
$double = bcadd($s,'0',2);

PHP: bcadd

How do I add an image to a JButton

You put your image in resources folder and use follow code:

JButton btn = new JButton("");
btn.setIcon(new ImageIcon(Class.class.getResource("/resources/img.png")));

Redirect stdout to a file in Python?

Here is a variation of Yuda Prawira answer:

  • implement flush() and all the file attributes
  • write it as a contextmanager
  • capture stderr also


import contextlib, sys

def log_print(file):
    # capture all outputs to a log file while still printing it
    class Logger:
        def __init__(self, file):
            self.terminal = sys.stdout
            self.log = file

        def write(self, message):

        def __getattr__(self, attr):
            return getattr(self.terminal, attr)

    logger = Logger(file)

    _stdout = sys.stdout
    _stderr = sys.stderr
    sys.stdout = logger
    sys.stderr = logger
        yield logger.log
        sys.stdout = _stdout
        sys.stderr = _stderr

with log_print(open('mylogfile.log', 'w')):
    print('hello world')
    print('hello world on stderr', file=sys.stderr)

# you can capture the output to a string with:
# with log_print(io.StringIO()) as log:
#   ....
#   print('[captured output]', log.getvalue())

Redirecting output to $null in PowerShell, but ensuring the variable remains set

using a function:

function run_command ($command)
    invoke-expression "$command *>$null"
    return $_

if (!(run_command "dir *.txt"))
    if (!(run_command "dir *.doc"))
        run_command "dir *.*"

or if you like one-liners:

function run_command ($command) { invoke-expression "$command  "|out-null; return $_ }

if (!(run_command "dir *.txt")) { if (!(run_command "dir *.doc")) { run_command "dir *.*" } }

How to install a specific JDK on Mac OS X?

JDK is the Java Development Kit (used to develop Java software).

JRE is the Java Runtime Environment (used to run any .jar file 'Java software').

The JDK contains a JRE inside it.

On Windows when you update Java, it updates the JRE automatically.

On Mac you do not have a JRE separated you have it, but inside the JDK, so when you update Java it will update your JRE which is inside your JDK; it doesn't install an JDK for you. You need to get it from somewhere else.

Git checkout - switching back to HEAD

You can stash (save the changes in temporary box) then, back to master branch HEAD.

$ git add .
$ git stash
$ git checkout master

Jump Over Commits Back and Forth:

  • Go to a specific commit-sha.

      $ git checkout <commit-sha>
  • If you have uncommitted changes here then, you can checkout to a new branch | Add | Commit | Push the current branch to the remote.

      # checkout a new branch, add, commit, push
      $ git checkout -b <branch-name>
      $ git add .
      $ git commit -m 'Commit message'
      $ git push origin HEAD          # push the current branch to remote 
      $ git checkout master           # back to master branch now
  • If you have changes in the specific commit and don't want to keep the changes, you can do stash or reset then checkout to master (or, any other branch).

      # stash
      $ git add -A
      $ git stash
      $ git checkout master
      # reset
      $ git reset --hard HEAD
      $ git checkout master
  • After checking out a specific commit if you have no uncommitted change(s) then, just back to master or other branch.

      $ git status          # see the changes
      $ git checkout master
      # or, shortcut
      $ git checkout -      # back to the previous state

Downloading folders from aws s3, cp or sync?

In the case you want to download a single file, you can try the following command:

aws s3 cp s3://bucket/filename /path/to/dest/folder

Mocking Logger and LoggerFactory with PowerMock and Mockito

Somewhat late to the party - I was doing something similar and needed some pointers and ended up here. Taking no credit - I took all of the code from Brice but got the "zero interactions" than Cengiz got.

Using guidance from what jheriks amd Joseph Lust had put I think I know why - I had my object under test as a field and newed it up in a @Before unlike Brice. Then the actual logger was not the mock but a real class init'd as jhriks suggested...

I would normally do this for my object under test so as to get a fresh object for each test. When I moved the field to a local and newed it in the test it ran ok. However, if I tried a second test it was not the mock in my test but the mock from the first test and I got the zero interactions again.

When I put the creation of the mock in the @BeforeClass the logger in the object under test is always the mock but see the note below for the problems with this...

Class under test

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyClassWithSomeLogging  {

    private static final Logger LOG = LoggerFactory.getLogger(MyClassWithSomeLogging.class);

    public void doStuff(boolean b) {
        if(b) {
        } else {



import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.mockito.Mockito.*;
import static org.powermock.api.mockito.PowerMockito.mock;
import static org.powermock.api.mockito.PowerMockito.*;
import static org.powermock.api.mockito.PowerMockito.when;

public class MyClassWithSomeLoggingTest {

    private static Logger mockLOG;

    public static void setup() {
        mockLOG = mock(Logger.class);

    public void testIt() {
        MyClassWithSomeLogging myClassWithSomeLogging = new MyClassWithSomeLogging();

        verify(mockLOG, times(1)).info("true");

    public void testIt2() {
        MyClassWithSomeLogging myClassWithSomeLogging = new MyClassWithSomeLogging();

        verify(mockLOG, times(1)).info("false");

    public static void verifyStatic() {
        verify(mockLOG, times(1)).info("true");
        verify(mockLOG, times(1)).info("false");
        verify(mockLOG, times(2)).info(anyString());


If you have two tests with the same expectation I had to do the verify in the @AfterClass as the invocations on the static are stacked up - verify(mockLOG, times(2)).info("true"); - rather than times(1) in each test as the second test would fail saying there where 2 invocation of this. This is pretty pants but I couldn't find a way to clear the invocations. I'd like to know if anyone can think of a way round this....

jquery - Click event not working for dynamically created button

the simple and easy way to do that is use on event:


but we can say this is not the best way to do this. I suggest a another way to do this is use clone() method instead of using dynamic html. Write some html in you file for example:

<div id='div1'></div>

Now in the script tag make a clone of this div then all the properties of this div would follow with new element too. For Example:

var dynamicDiv = jQuery('#div1').clone(true);

Now use the element dynamicDiv wherever you want to add it or change its properties as you like. Now all jQuery functions will work with this element

SOAP request in PHP with CURL

Tested and working!

  • with https, user & password

     //Data, connection, auth
     $dataFromTheForm = $_POST['fieldName']; // request data from the form
     $soapUrl = ""; // asmx URL of WSDL
     $soapUser = "username";  //  username
     $soapPassword = "password"; // password
     // xml post structure
     $xml_post_string = '<?xml version="1.0" encoding="utf-8"?>
                         <soap:Envelope xmlns:xsi="" xmlns:xsd="" xmlns:soap="">
                             <GetItemPrice xmlns=""> // xmlns value to be set to your WSDL URL
                             </GetItemPrice >
                         </soap:Envelope>';   // data from the form, e.g. some ID number
        $headers = array(
                     "Content-type: text/xml;charset=\"utf-8\"",
                     "Accept: text/xml",
                     "Cache-Control: no-cache",
                     "Pragma: no-cache",
                     "Content-length: ".strlen($xml_post_string),
                 ); //SOAPAction: your op URL
         $url = $soapUrl;
         // PHP cURL  for https connection with auth
         $ch = curl_init();
         curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
         curl_setopt($ch, CURLOPT_URL, $url);
         curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
         curl_setopt($ch, CURLOPT_USERPWD, $soapUser.":".$soapPassword); // username and password - declared at the top of the doc
         curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
         curl_setopt($ch, CURLOPT_TIMEOUT, 10);
         curl_setopt($ch, CURLOPT_POST, true);
         curl_setopt($ch, CURLOPT_POSTFIELDS, $xml_post_string); // the SOAP request
         curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
         // converting
         $response = curl_exec($ch); 
         // converting
         $response1 = str_replace("<soap:Body>","",$response);
         $response2 = str_replace("</soap:Body>","",$response1);
         // convertingc to XML
         $parser = simplexml_load_string($response2);
         // user $parser to get your data out of XML response and to display it. 

How to find specified name and its value in JSON-string from Java?

I agree that Google's Gson is clear and easy to use. But you should create a result class for getting an instance from JSON string. If you can't clarify the result class, use json-simple:

// import static;
// import static org.junit.Assert.assertThat;
// import org.json.simple.JSONObject;
// import org.json.simple.JSONValue;
// import org.junit.Test;

public void json2Object() {
    // given
    String jsonString = "{\"name\" : \"John\",\"age\" : \"20\","
            + "\"address\" : \"some address\","
            + "\"someobject\" : {\"field\" : \"value\"}}";

    // when
    JSONObject object = (JSONObject) JSONValue.parse(jsonString);

    // then
    Set<String> keySet = object.keySet();
    for (String key : keySet) {
        Object value = object.get(key);
        System.out.printf("%s=%s (%s)\n", key, value, value.getClass()

    assertThat(object.get("age").toString(), is("20"));

Pros and cons of Gson and json-simple is pretty much like pros and cons of user-defined Java Object and Map. The object you define is clear for all fields (name and type), but less flexible than Map.

How to send a Post body in the HttpClient request in Windows Phone 8?

This depends on what content do you have. You need to initialize your requestMessage.Content property with new HttpContent. For example:

// Add request body
if (isPostRequest)
    requestMessage.Content = new ByteArrayContent(content);

where content is your encoded content. You also should include correct Content-type header.


Oh, it can be even nicer (from this answer):

requestMessage.Content = new StringContent("{\"name\":\"John Doe\",\"age\":33}", Encoding.UTF8, "application/json");

Get local href value from anchor (a) tag

document.getElementById("link").getAttribute("href"); If you have more than one <a> tag, for example:

    <a href="1"></a>_x000D_
    <a href="2"></a>_x000D_
    <a href="3"></a>_x000D_

You can do it like this: document.getElementById("link")[0].getAttribute("href"); to access the first array of <a> tags, or depends on the condition you make.

SUM of grouped COUNT in SQL Query

all of the solution here are great but not necessarily can be implemented for old mysql servers (at least at my case). so you can use sub-queries (i think it is less complicated).

 select sum(t1.cnt) from 
        (SELECT column, COUNT(column) as cnt
            GROUP BY 
            COUNT(column) > 1) as t1 ;

How do I set proxy for chrome in python webdriver?

This worked for me like a charm:

proxy = "localhost:8080"
desired_capabilities = webdriver.DesiredCapabilities.CHROME.copy()
desired_capabilities['proxy'] = {
    "httpProxy": proxy,
    "ftpProxy": proxy,
    "sslProxy": proxy,
    "noProxy": None,
    "proxyType": "MANUAL",
    "class": "org.openqa.selenium.Proxy",
    "autodetect": False

Best algorithm for detecting cycles in a directed graph

If a graph satisfy this property

|e| > |v| - 1

then the graph contains at least on cycle.

How to Convert Boolean to String

Another way to do : json_encode( booleanValue )

echo json_encode(true);  // string "true"

echo json_encode(false); // string "false"

// null !== false
echo json_encode(null);  // string "null"

Case statement in MySQL

Another thing to keep in mind is there are two different CASEs with MySQL: one like what @cdhowie and others describe here (and documented here: and something which is called a CASE, but has completely different syntax and completely different function, documented here:

Invariably, I first use one when I want the other.

How to programmatically round corners and set random background colors

Instead of setBackgroundColor, retrieve the background drawable and set its color:


GradientDrawable drawable = (GradientDrawable) v.getBackground();
if (i % 2 == 0) {
} else {

Also, you can define the padding within your tags_rounded_corners.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="">
  <corners android:radius="4dp" />
    android:right="2dp" />

How to clear mysql screen console in windows?

On linux : you can use ctrl + L or type command system clear.

How a thread should close itself in Java?

Thread is a class, not an instance; currentThread() is a static method that returns the Thread instance corresponding to the calling thread.

Use (2). interrupt() is a bit brutal for normal use.

Doing a join across two databases with different collations on SQL Server and getting an error

You can use the collate clause in a query (I can't find my example right now, so my syntax is probably wrong - I hope it points you in the right direction)

select sone_field collate SQL_Latin1_General_CP850_CI_AI
  from table_1
    inner join table_2
      on (table_1.field collate SQL_Latin1_General_CP850_CI_AI = table_2.field)
  where whatever

How to increase the execution timeout in php?

If you cannot edit php.ini (on your server for example) you can attempt to change the php.ini parameters from within your php code. Try:

ini_set('max_execution_time', 'NUMBER OF SECONDS TO ALLOW BEFORE TIMEOUT');

If that doesn't work, try also setting 'set_time_limit' in the same way, beyond that I'd say your only option is to contact your host. These settings cannot be modified while in safe mode.

Is it a good idea to index datetime field in mysql?

MySQL recommends using indexes for a variety of reasons including elimination of rows between conditions:

This makes your datetime column an excellent candidate for an index if you are going to be using it in conditions frequently in queries. If your only condition is BETWEEN NOW() AND DATE_ADD(NOW(), INTERVAL 30 DAY) and you have no other index in the condition, MySQL will have to do a full table scan on every query. I'm not sure how many rows are generated in 30 days, but as long as it's less than about 1/3 of the total rows it will be more efficient to use an index on the column.

Your question about creating an efficient database is very broad. I'd say to just make sure that it's normalized and all appropriate columns are indexed (i.e. ones used in joins and where clauses).

What is the difference between UTF-8 and ISO-8859-1?

From another perspective, files that both unicode and ascii encodings fail to read because they have a byte 0xc0 in them, seem to get read by iso-8859-1 properly. The caveat is that the file shouldn't have unicode characters in it of course.

How can I detect if this dictionary key exists in C#?

You can use ContainsKey:

if (dict.ContainsKey(key)) { ... }

or TryGetValue:

dict.TryGetValue(key, out value);

Update: according to a comment the actual class here is not an IDictionary but a PhysicalAddressDictionary, so the methods are Contains and TryGetValue but they work in the same way.

Example usage:

PhysicalAddressEntry entry;
PhysicalAddressKey key = c.PhysicalAddresses[PhysicalAddressKey.Home].Street;
if (c.PhysicalAddresses.TryGetValue(key, out entry))
    row["HomeStreet"] = entry;

Update 2: here is the working code (compiled by question asker)

PhysicalAddressEntry entry;
PhysicalAddressKey key = PhysicalAddressKey.Home;
if (c.PhysicalAddresses.TryGetValue(key, out entry))
    if (entry.Street != null)
        row["HomeStreet"] = entry.Street.ToString();

...with the inner conditional repeated as necessary for each key required. The TryGetValue is only done once per PhysicalAddressKey (Home, Work, etc).

bootstrap multiselect get selected values

In your Html page please add

<!DOCTYPE html>
<html lang="en">
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Test the multiselect with ajax</title>

    <!-- Bootstrap -->
    <link rel="stylesheet" href="">
    <link rel="stylesheet" href="">
    <!-- Bootstrap multiselect -->
    <link rel="stylesheet" href="">

    <!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
    <!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
    <!--[if lt IE 9]>
      <script src=""></script>
      <script src=""></script>
    <div class="container">

      <form method="post" id="myForm">

        <!-- Build your select: -->
        <select name="categories[]" id="example-getting-started" multiple="multiple" class="col-md-12">
          <option value="A">Cheese</option>
          <option value="B">Tomatoes</option>
          <option value="C">Mozzarella</option>
          <option value="D">Mushrooms</option>
          <option value="E">Pepperoni</option>
          <option value="F">Onions</option>
          <option value="G">10</option>
          <option value="H">11</option>
          <option value="I">12</option>
        <button type="button" class="btnSubmit"> Send </button>


      <div id="result">result</div>

    <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
    <script src=""></script>
    <!-- Include all compiled plugins (below), or include individual files as needed -->
    <script src=""></script>
    <!-- Bootstrap multiselect -->
    <script src=""></script>

    <!-- Bootstrap multiselect -->
    <script src="ajax.js"></script>

    <!-- Initialize the plugin: -->
    <script type="text/javascript">
      $(document).ready(function() {




In your ajax.js page please add

$(document).ready(function () {
  $(".btnSubmit").on('click',(function(event) {
    var formData = new FormData($('#myForm')[0]);
      url: "action.php",
      type: "POST",
      data: formData,
      contentType: false,
      cache: false,
      success: function(data)

        // To clear the selected options
        var select = $("#example-getting-started");
        if (data.d) {
          $(data.d).each(function(key,value) {
        $('#example-getting-started').multiselect({includeSelectAllOption: true});

      error: function()
        console.log("failed to send the data");

In your action.php page add

  echo "<b>You selected :</b>";


    echo $_POST['categories'][$i]."<br>";


how do I get the bullet points of a <ul> to center with the text?

You can do that with list-style-position: inside; on the ul element :

ul {
    list-style-position: inside;

See working fiddle

How do I delete everything below row X in VBA/Excel?

This function will clear the sheet data starting from specified row and column :

Sub ClearWKSData(wksCur As Worksheet, iFirstRow As Integer, iFirstCol As Integer)

Dim iUsedCols As Integer
Dim iUsedRows As Integer

iUsedRows = wksCur.UsedRange.Row + wksCur.UsedRange.Rows.Count - 1
iUsedCols = wksCur.UsedRange.Column + wksCur.UsedRange.Columns.Count - 1

If iUsedRows > iFirstRow And iUsedCols > iFirstCol Then
    wksCur.Range(wksCur.Cells(iFirstRow, iFirstCol), wksCur.Cells(iUsedRows, iUsedCols)).Clear
End If

End Sub

How to select an element with 2 classes

Just chain them together:

.a.b {
  color: #666;

How to uncompress a tar.gz in another directory

You can use for loop to untar multiple .tar.gz files to another folder. The following code will take /destination/folder/path as an argument to the script and untar all .tar.gz files present at the current location in /destination/folder/path.

if [ $# -ne 1 ];
 echo "invalid argument/s"
 echo "Usage: ./ /target/directory"
 exit 0
for file in *.tar.gz
    tar -zxvf "$file" --directory $1

Disable future dates after today in Jquery Ui Datepicker

In case you are appending Dtpicker,use the following code

    "dateOnly": true,
    "dateFormat": "YYYY-MM-DD",
    "closeOnSelected": true,
    maxDate: new Date()         

SQL: Group by minimum value in one field while selecting distinct rows

The below query takes the first date for each work order (in a table of showing all status changes):

    DATE >= to_date('2015-01-01','YYYY-MM-DD')

Absolute position of an element on the screen using jQuery

See .offset() here in the jQuery doc. It gives the position relative to the document, not to the parent. You perhaps have .offset() and .position() confused. If you want the position in the window instead of the position in the document, you can subtract off the .scrollTop() and .scrollLeft() values to account for the scrolled position.

Here's an excerpt from the doc:

The .offset() method allows us to retrieve the current position of an element relative to the document. Contrast this with .position(), which retrieves the current position relative to the offset parent. When positioning a new element on top of an existing one for global manipulation (in particular, for implementing drag-and-drop), .offset() is the more useful.

To combine these:

var offset = $("selector").offset();
var posY = - $(window).scrollTop();
var posX = offset.left - $(window).scrollLeft(); 

You can try it here (scroll to see the numbers change):

javascript setTimeout() not working

To make little more easy to understand use like below, which i prefer the most. Also it permits to call multiple function at once. Obviously

}, startInterval);

I want to exception handle 'list index out of range.'

for i in range (1, len(list))
        print (list[i])

    except ValueError:
        print("Error Value.")
    except indexError:
        print("Erorr index")
    except :
        print('error ')

Managing jQuery plugin dependency in webpack

Edit: Sometimes you want to use webpack simply as a module bundler for a simple web project - to keep your own code organized. The following solution is for those who just want an external library to work as expected inside their modules - without using a lot of time diving into webpack setups. (Edited after -1)

Quick and simple (es6) solution if you’re still struggling or want to avoid externals config / additional webpack plugin config:

<script src="cdn/jquery.js"></script>
<script src="cdn/underscore.js"></script>
<script src="etc.js"></script>
<script src="bundle.js"></script>

inside a module:

const { jQuery: $, Underscore: _, etc } = window;

How to parse XML to R data frame

Data in XML format are rarely organized in a way that would allow the xmlToDataFrame function to work. You're better off extracting everything in lists and then binding the lists together in a data frame:

data <- xmlParse("")

xml_data <- xmlToList(data)

In the case of your example data, getting location and start time is fairly straightforward:

location <- as.list(xml_data[["data"]][["location"]][["point"]])

start_time <- unlist(xml_data[["data"]][["time-layout"]][
    names(xml_data[["data"]][["time-layout"]]) == "start-valid-time"])

Temperature data is a bit more complicated. First you need to get to the node that contains the temperature lists. Then you need extract both the lists, look within each one, and pick the one that has "hourly" as one of its values. Then you need to select only that list but only keep the values that have the "value" label:

temps <- xml_data[["data"]][["parameters"]]
temps <- temps[names(temps) == "temperature"]
temps <- temps[sapply(temps, function(x) any(unlist(x) == "hourly"))]
temps <- unlist(temps[[1]][sapply(temps, names) == "value"])

out <- data.frame(
  "start_valid_time" = start_time,
  "hourly_temperature" = temps)

  latitude longitude          start_valid_time hourly_temperature
1    29.81    -82.42 2013-06-19T16:00:00-04:00                 91
2    29.81    -82.42 2013-06-19T17:00:00-04:00                 90
3    29.81    -82.42 2013-06-19T18:00:00-04:00                 89
4    29.81    -82.42 2013-06-19T19:00:00-04:00                 85
5    29.81    -82.42 2013-06-19T20:00:00-04:00                 83
6    29.81    -82.42 2013-06-19T21:00:00-04:00                 80

How to atomically delete keys matching a pattern using Redis

Other answers may not work if your key contains special chars - Guide$CLASSMETADATA][1] for instance. Wrapping each key into quotes will ensure they get properly deleted:

redis-cli --scan --pattern sf_* | awk '{print $1}' | sed "s/^/'/;s/$/'/" | xargs redis-cli del

Using variable in SQL LIKE statement

If you are using a Stored Procedure:

    @PartialName VARCHAR(50) = NULL

    FROM <table>
    WHERE Name LIKE '%' + @PartialName + '%'

Relative paths in Python

This code will return the absolute path to the main script.

import os
def whereAmI():
    return os.path.dirname(os.path.realpath(__import__("__main__").__file__))

This will work even in a module.

rmagick gem install "Can't find Magick-config"

in ubuntu 15.10

sudo apt-get install graphicsmagick-libmagick-dev-compat

did the trick for me

Postgres where clause compare timestamp

Assuming you actually mean timestamp because there is no datetime in Postgres

Cast the timestamp column to a date, that will remove the time part:

select *
from the_table
where the_timestamp_column::date = date '2015-07-15';

This will return all rows from July, 15th.

Note that the above will not use an index on the_timestamp_column. If performance is critical, you need to either create an index on that expression or use a range condition:

select *
from the_table
where the_timestamp_column >= timestamp '2015-07-15 00:00:00'
  and the_timestamp_column < timestamp '2015-07-16 00:00:00';

Configure apache to listen on port other than 80

For FC22 server

cd /etc/httpd/conf edit httpd.conf [enter]

Change: Listen 80 to: Listen whatevernumber

Save the file

systemctl restart httpd.service [enter] if required, open whatevernumber in your router / firewall

IE 8: background-size fix

As posted by 'Dan' in a similar thread, there is a possible fix if you're not using a sprite:

How do I make background-size work in IE?

filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(

-ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(

However, this scales the entire image to fit in the allocated area. So if your using a sprite, this may cause issues.

The filter has a flaw, any links inside the allocated area are no longer clickable.

How to make `setInterval` behave more in sync, or how to use `setTimeout` instead?

function appendTaskOnStack(task, ms, loop) {
    window.nextTaskAfter = (window.nextTaskAfter || 0) + ms;

    if (!loop) {
        setTimeout(function() {
            appendTaskOnStack(task, ms, true);
        }, window.nextTaskAfter);
    else {
        if (task) 
        window.nextTaskAfter = 0;

for (var n=0; n < 10; n++) {
    }, 100);

CSS to make HTML page footer stay at bottom of the page with a minimum height, but not overlap the page

I have used in my many projects and never got any single issue :)

for your reference, Code are in snippet

* {_x000D_
 margin: 0;_x000D_
html, body {_x000D_
 height: 100%;_x000D_
.wrapper {_x000D_
 min-height: 100%;_x000D_
 height: auto !important; /* This line and the next line are not necessary unless you need IE6 support */_x000D_
 height: 100%;_x000D_
 margin: 0 auto -50px; /* the bottom margin is the negative value of the footer's height */_x000D_
.footer, .push {_x000D_
 height: 50px; /* .push must be the same height as .footer */_x000D_
<meta charset="utf-8">_x000D_
<title>Untitled Document</title>_x000D_
  <div class="wrapper">_x000D_
    Content Area_x000D_
  <div class="push">_x000D_
  <div class="footer">_x000D_
    Footer Area_x000D_

What's the meaning of exception code "EXC_I386_GPFLT"?

I wondered why this appeared during my unit tests.

I have added a method declaration to a protocol which included throws; but the potentially throwing method wasn't even used in that particular test. Enabling Zombies in test sounded like too much trouble.

Turns out a ?K clean did the trick. I'm always flabberghasted when that solves actual problems.

How line ending conversions work with git core.autocrlf between different operating systems

The best explanation of how core.autocrlf works is found on the gitattributes man page, in the text attribute section.

This is how core.autocrlf appears to work currently (or at least since v1.7.2 from what I am aware):

  • core.autocrlf = true
  1. Text files checked-out from the repository that have only LF characters are normalized to CRLF in your working tree; files that contain CRLF in the repository will not be touched
  2. Text files that have only LF characters in the repository, are normalized from CRLF to LF when committed back to the repository. Files that contain CRLF in the repository will be committed untouched.
  • core.autocrlf = input
  1. Text files checked-out from the repository will keep original EOL characters in your working tree.
  2. Text files in your working tree with CRLF characters are normalized to LF when committed back to the repository.
  • core.autocrlf = false
  1. core.eol dictates EOL characters in the text files of your working tree.
  2. core.eol = native by default, which means Windows EOLs are CRLF and *nix EOLs are LF in working trees.
  3. Repository gitattributes settings determines EOL character normalization for commits to the repository (default is normalization to LF characters).

I've only just recently researched this issue and I also find the situation to be very convoluted. The core.eol setting definitely helped clarify how EOL characters are handled by git.

Read MS Exchange email in C#

One option is to use Outlook. We have a mail manager application that access an exchange server and uses outlook as the interface. Its dirty but it works.

Example code:

public Outlook.MAPIFolder getInbox()
            mailSession = new Outlook.Application();
            mailNamespace = mailSession.GetNamespace("MAPI");
            mailNamespace.Logon(mail_username, mail_password, false, true);
            return MailNamespace.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox);


You can also modify your config/routes.rb file like:

 get 'ajax/:action', to: 'ajax#:action', :defaults => { :format => 'json' }

Which will default the format to json. It is working fine for me in Rails 4.

Or if you want to go even further and you are using namespaces, you can cut down the duplicates:

namespace :api, defaults: {format: 'json'} do
   #your controller routes here ...

with the above everything under /api will be formatted as json by default.

How to randomly select rows in SQL?

Maybe this site will be of assistance.

For those who don't want to click through:

SELECT TOP 1 column FROM table

How can I expose more than 1 port with Docker?

If you are creating a container from an image and like to expose multiple ports (not publish) you can use the following command:

docker create --name `container name` --expose 7000 --expose 7001 `image name`

Now, when you start this container using the docker start command, the configured ports above will be exposed.

How do I check what version of Python is running my script?

The simplest way

Just type python in your terminal and you can see the version as like following

desktop:~$ python
Python 2.7.6 (default, Jun 22 2015, 18:00:18) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

How do I define a method which takes a lambda as a parameter in Java 8?

There is flexibility in using lambda as parameter. It enables functional programming in java. The basic syntax is

param -> method_body

Following is a way, you can define a method taking functional interface (lambda is used) as parameter. a. if you wish to define a method declared inside a functional interface, say, the functional interface is given as an argument/parameter to a method called from main()

interface FInterface{
    int callMeLambda(String temp);

class ConcreteClass{
    void funcUsesAnonymousOrLambda(FInterface fi){
        System.out.println("===Executing method arg instantiated with Lambda==="));
    public static void main(){
        // calls a method having FInterface as an argument.
        funcUsesAnonymousOrLambda(new FInterface() {
            int callMeLambda(String temp){ //define callMeLambda(){} here..
                return 0;
/***********Can be replaced by Lambda below*********/
        funcUsesAnonymousOrLambda( (x) -> {
            return 0; //(1)

FInterface fi = (x) -> { return 0; };


Here above it can be seen, how a lambda expression can be replaced with an interface.

Above explains a particular usage of lambda expression, there are more. ref Java 8 lambda within a lambda can't modify variable from outer lambda

Android Gradle plugin 0.7.0: "duplicate files during packaging of APK"

The same problem when I used '' in Android Studio 1.0.1. I need include this in build.gradle

        exclude 'META-INF/notice.txt'
        exclude 'META-INF/license.txt'

Is JavaScript object-oriented?

Is JavaScript object-oriented?

Answer : Yes

It has objects which can contain data and methods that act upon that data. Objects can contain other objects.

  • It does not have classes, but it does have constructors which do what classes do, including acting as containers for class variables and methods.
  • It does not have class-oriented inheritance, but it does have prototype-oriented inheritance.

The two main ways of building up object systems are by inheritance (is-a) and by aggregation (has-a). JavaScript does both, but its dynamic nature allows it to excel at aggregation.

Some argue that JavaScript is not truly object oriented because it does not provide information hiding. That is, objects cannot have private variables and private methods: All members are public.

But it turns out that JavaScript objects can have private variables and private methods. (Click here now to find out how.) Of course, few understand this because JavaScript is the world's most misunderstood programming language.

Some argue that JavaScript is not truly object oriented because it does not provide inheritance. But it turns out that JavaScript supports not only classical inheritance, but other code reuse patterns as well.

Sources :

Removing elements from array Ruby

You may do:

a= [1,1,1,2,2,3]
delete_list = [1,3]
delete_list.each do |del|

result : [1, 1, 2, 2]

SQL Server Case Statement when IS NULL

In this situation you can use ISNULL() function instead of CASE expression


How to end a session in ExpressJS


The above did not work for me so I did this.

req.session.cookie.expires = new Date().getTime();

By setting the expiration of the cookie to the current time, the session expired on its own.

Entity Framework vs LINQ to SQL

Neither yet supports the unique SQL 2008 datatypes. The difference from my perspective is that Entity still has a chance to construct a model around my geographic datatype in some future release, and Linq to SQL, being abandoned, never will.

Wonder what's up with nHibernate, or OpenAccess...

How do you discover model attributes in Rails?


Source: blog

Eventviewer eventid for lock and unlock

To identify unlock screen I believe that you can use ID 4624. But then you also need to look at the Logon Type which in this case is 7:

Event ID for Logoff is 4634

How do I measure the execution time of JavaScript code with callbacks?

You could also try exectimer. It gives you feedback like:

var t = require("exectimer");

var myFunction() {
   var tick = new t.tick("myFunction");
   // do some processing and end this tick

// Display the results
console.log(t.timers.myFunction.duration()); // total duration of all ticks
console.log(t.timers.myFunction.min()); // minimal tick duration
console.log(t.timers.myFunction.max()); // maximal tick duration
console.log(t.timers.myFunction.mean()); // mean tick duration
console.log(t.timers.myFunction.median()); // median tick duration

[edit] There is an even simpler way now to use exectime. Your code could be wrapped like this:

var t = require('exectimer'),
Tick = t.Tick;

for(var i = 1; i < LIMIT; i++){
    Tick.wrap(function saveUsers(done) {{id : i, name : "MongoUser [" + i + "]"}, function(err, saved) {
            if( err || !saved ) console.log("Error");
            else console.log("Saved");

// Display the results
console.log(t.timers.myFunction.duration()); // total duration of all ticks
console.log(t.timers.saveUsers.min()); // minimal tick duration
console.log(t.timers.saveUsers.max()); // maximal tick duration
console.log(t.timers.saveUsers.mean()); // mean tick duration
console.log(t.timers.saveUsers.median()); // median tick duration

How to implement band-pass Butterworth filter with Scipy.signal.butter

The filter design method in accepted answer is correct, but it has a flaw. SciPy bandpass filters designed with b, a are unstable and may result in erroneous filters at higher filter orders.

Instead, use sos (second-order sections) output of filter design.

from scipy.signal import butter, sosfilt, sosfreqz

def butter_bandpass(lowcut, highcut, fs, order=5):
        nyq = 0.5 * fs
        low = lowcut / nyq
        high = highcut / nyq
        sos = butter(order, [low, high], analog=False, btype='band', output='sos')
        return sos

def butter_bandpass_filter(data, lowcut, highcut, fs, order=5):
        sos = butter_bandpass(lowcut, highcut, fs, order=order)
        y = sosfilt(sos, data)
        return y

Also, you can plot frequency response by changing

b, a = butter_bandpass(lowcut, highcut, fs, order=order)
w, h = freqz(b, a, worN=2000)


sos = butter_bandpass(lowcut, highcut, fs, order=order)
w, h = sosfreqz(sos, worN=2000)

Set the default value in dropdownlist using jQuery

You can just do this:


Command to delete all pods in all kubernetes namespaces

I tried commands from listed answers here but pods were stuck in terminating state.
I found below command to delete all pods from particular namespace if stuck in terminating state or you are not able to delete it then you can delete pods forcefully.

kubectl delete pods --all --grace-period=0 --force --namespace namespace

Hope it might be useful to someone.

installing cPickle with python 3.5

cPickle comes with the standard library… in python 2.x. You are on python 3.x, so if you want cPickle, you can do this:

>>> import _pickle as cPickle

However, in 3.x, it's easier just to use pickle.

No need to install anything. If something requires cPickle in python 3.x, then that's probably a bug.

Does "git fetch --tags" include "git fetch"?

git fetch upstream --tags

works just fine, it will only get new tags and will not get any other code base.

Android button background color

This is my way to do custom Button with different color.`

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="" >
<stroke android:width="3dp"
        android:color="#80FFFFFF" />

  <corners android:radius="25dp" />

  <gradient android:angle="270"
            android:startColor="#90150517" />

This way you set as background.

<Button android:id="@+id/button"

Get MD5 hash of big files in Python

Using multiple comment/answers in this thread, here is my solution :

import hashlib
def md5_for_file(path, block_size=256*128, hr=False):
    Block size directly depends on the block size of your filesystem
    to avoid performances issues
    Here I have blocks of 4096 octets (Default NTFS)
    md5 = hashlib.md5()
    with open(path,'rb') as f: 
        for chunk in iter(lambda:, b''): 
    if hr:
        return md5.hexdigest()
    return md5.digest()
  • This is "pythonic"
  • This is a function
  • It avoids implicit values: always prefer explicit ones.
  • It allows (very important) performances optimizations

And finally,

- This has been built by a community, thanks all for your advices/ideas.

Accessing post variables using Java Servlets

Your HttpServletRequest object has a getParameter(String paramName) method that can be used to get parameter values.

How can I stop the browser back button using JavaScript?

This is the way I could it accomplish it.

Weirdly, changing window.location didn't work out fine in Google Chrome and Safari.

It happens that location.hash doesn't create an entry in the history for Chrome and Safari. So you will have to use the pushstate.

This is working for me in all browsers.

history.pushState({ page: 1 }, "title 1", "#nbb");
window.onhashchange = function (event) {
    window.location.hash = "nbb";

javascript scroll event for iPhone/iPad?

I was able to get a great solution to this problem with iScroll, with the feel of momentum scrolling and everything The github doc is great, and I mostly followed it. Here's the details of my implementation.

HTML: I wrapped the scrollable area of my content in some divs that iScroll can use:

<div id="wrapper">
  <div id="scroller">
    ... my scrollable content

CSS: I used the Modernizr class for "touch" to target my style changes only to touch devices (because I only instantiated iScroll on touch).

.touch #wrapper {
  position: absolute;
  z-index: 1;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  overflow: hidden;
.touch #scroller {
  position: absolute;
  z-index: 1;
  width: 100%;

JS: I included iscroll-probe.js from the iScroll download, and then initialized the scroller as below, where updatePosition is my function that reacts to the new scroll position.

# coffeescript
if Modernizr.touch
  myScroller = new IScroll('#wrapper', probeType: 3)
  myScroller.on 'scroll', updatePosition
  myScroller.on 'scrollEnd', updatePosition

You have to use myScroller to get the current position now, instead of looking at the scroll offset. Here is a function taken from (a super helpful article, but a little out of date now)

function getScroll(elem, iscroll) {   
  var x, y;

  if (Modernizr.touch && iscroll) {
    x = iscroll.x * -1;
    y = iscroll.y * -1;   
  } else {
    x = elem.scrollTop;
    y = elem.scrollLeft;   

  return {x: x, y: y}; 

The only other gotcha was occasionally I would lose part of my page that I was trying to scroll to, and it would refuse to scroll. I had to add in some calls to myScroller.refresh() whenever I changed the contents of the #wrapper, and that solved the problem.

EDIT: Another gotcha was that iScroll eats all the "click" events. I turned on the option to have iScroll emit a "tap" event and handled those instead of "click" events. Thankfully I didn't need much clicking in the scroll area, so this wasn't a big deal.

You must add a reference to assembly 'netstandard, Version=

I was facing this problem when trying to add a .NETStandard dependency to a .NET4.6.1 library, and compiling it in Linux with Mono 4.6.2 (the version that comes with Ubuntu 16.04).

I finally solved it today; the solution requires to do both of these things:

  1. Change <TargetFrameworkVersion>v4.6.1</TargetFrameworkVersion> to <TargetFrameworkVersion>v4.7.1</TargetFrameworkVersion> in the .csproj file.
  2. Upgrade your mono to a newer version. I believe 5.x should work, but to be sure, you can just install Ubuntu 20.04 (which at the time of writing is only in preview), which includes Mono

Error Installing Homebrew - Brew Command Not Found

Check XCode is installed or not.

gcc --version
ruby -e "$(curl -fsSL"
brew doctor
brew update "click here for exact instruction updates"

How can I insert data into Database Laravel?

make sure you use the POST to insert the data. Actually you were using GET.

Proxy Basic Authentication in C#: HTTP 407 error

here is the correct way of using proxy along with creds..

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);

IWebProxy proxy = request.Proxy;                    
if (proxy != null)
    Console.WriteLine("Proxy: {0}", proxy.GetProxy(request.RequestUri));
    Console.WriteLine("Proxy is null; no proxy will be used");

WebProxy myProxy = new WebProxy();
Uri newUri = new Uri("");
// Associate the newUri object to 'myProxy' object so that new myProxy settings can be set.
myProxy.Address = newUri;
// Create a NetworkCredential object and associate it with the 
// Proxy property of request object.
myProxy.Credentials = new NetworkCredential("userName", "password");
request.Proxy = myProxy;

Thanks everyone for help... :)

Difference between natural join and inner join

  • An inner join is one where the matching row in the joined table is required for a row from the first table to be returned
  • An outer join is one where the matching row in the joined table is not required for a row from the first table to be returned
  • A natural join is a join (you can have either natural left or natural right) that assumes the join criteria to be where same-named columns in both table match

I would avoid using natural joins like the plague, because natural joins are:

  • not standard sql [SQL 92] and therefore not portable, not particularly readable (by most SQL coders) and possibly not supported by various tools/libraries
  • not informative; you can't tell what columns are being joined on without referring to the schema
  • your join conditions are invisibly vulnerable to schema changes - if there are multiple natural join columns and one such column is removed from a table, the query will still execute, but probably not correctly and this change in behaviour will be silent
  • hardly worth the effort; you're only saving about 10 seconds of typing

Rails raw SQL example

You can do direct SQL to have a single query for both tables. I'll provide a sanitized query example to hopefully keep people from putting variables directly into the string itself (SQL injection danger), even though this example didn't specify the need for it:

@results = []
   ["... your SQL query goes here and ?, ?, ? are replaced...;", a, b, c])
).each do |record|
  # instead of an array of hashes, you could put in a custom object with attributes
  @results << {col_a_name: record["col_a_name"], col_b_name: record["col_b_name"], ...}

Edit: as Huy said, a simple way is ActiveRecord::Base.connection.execute("..."). Another way is ActiveRecord::Base.connection.exec_query('...').rows. And you can use native prepared statements, e.g. if using postgres, prepared statement can be done with raw_connection, prepare, and exec_prepared as described in

You can also put raw SQL fragments into ActiveRecord relational queries: and in associations, scopes, etc. You could probably construct the same SQL with ActiveRecord relational queries and can do cool things with ARel as Ernie mentions in And, of course there are other ORMs, gems, etc.

If this is going to be used a lot and adding indices won't cause other performance/resource issues, consider adding an index in the DB for payment_details.created_at and for payment_errors.created_at.

If lots of records and not all records need to show up at once, consider using pagination:

If you need to paginate, consider creating a view in the DB first called payment_records which combines the payment_details and payment_errors tables, then have a model for the view (which will be read-only). Some DBs support materialized views, which might be a good idea for performance.

Also consider hardware or VM specs on Rails server and DB server, config, disk space, network speed/latency/etc., proximity, etc. And consider putting DB on different server/VM than the Rails app if you haven't, etc.

How do browser cookie domains work?

Will be able to set cookie for .com?

No, but may be able to set a cookie for Firefox protects against this by maintaining a list of TLDs:

Apparently Internet Explorer doesn't allow two-letter domains to set cookies, which I suppose explains why simply redirects to I'd often wondered that.

JSON.parse vs. eval()

You are more vulnerable to attacks if using eval: JSON is a subset of Javascript and json.parse just parses JSON whereas eval would leave the door open to all JS expressions.

Searching for UUIDs in text with regex

[\w]{8}(-[\w]{4}){3}-[\w]{12} has worked for me in most cases.

Or if you want to be really specific [\w]{8}-[\w]{4}-[\w]{4}-[\w]{4}-[\w]{12}.

The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>)

Not really solve your question but it's an important alternative.

If you want to add custom html to the beginning of the page (inside <body> element), you may use Page.ClientScript.RegisterClientScriptBlock().

Although the method is called "script", but you can add arbitary string, including html.

How to fix Terminal not loading ~/.bashrc on OS X Lion

I have the following in my ~/.bash_profile:

if [ -f ~/.bashrc ]; then . ~/.bashrc; fi

If I had .bashrc instead of ~/.bashrc, I'd be seeing the same symptom you're seeing.

server error:405 - HTTP verb used to access this page is not allowed

In the Facebook app control panel make sure you have a forward slash on the end of any specified URL if you are only specifying a folder name


Page Tab URL:

Select all from table with Laravel and Eloquent

There are 3 ways that one can do that.


$entireTable = TableModelName::all();


$posts = Posts::get(); 
  1. put this line before the class in the controller

    use Illuminate\Support\Facades\DB; // this will import the DB facade into your controller class

Now in the class

$posts = DB::table('posts')->get(); // it will get the entire table
  1. put this line before the class in the controller

    Same import the DB facade like method 2

Now in the controller

$posts = DB::select('SELECT * FROM posts');

Looping each row in datagridview

Best aproach for me was:

  private void grid_receptie_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        int X = 1;
        foreach(DataGridViewRow row in grid_receptie.Rows)
            row.Cells["NR_CRT"].Value = X;

What's the use of ob_start() in php?

The accepted answer here describes what ob_start() does - not why it is used (which was the question asked).

As stated elsewhere ob_start() creates a buffer which output is written to.

But nobody has mentioned that it is possible to stack multiple buffers within PHP. See ob_get_level().

As to the why....

  1. Sending HTML to the browser in larger chunks gives a performance benefit from a reduced network overhead.

  2. Passing the data out of PHP in larger chunks gives a performance and capacity benefit by reducing the number of context switches required

  3. Passing larger chunks of data to mod_gzip/mod_deflate gives a performance benefit in that the compression can be more efficient.

  4. buffering the output means that you can still manipulate the HTTP headers later in the code

  5. explicitly flushing the buffer after outputting the [head]....[/head] can allow the browser to begin marshaling other resources for the page before HTML stream completes.

  6. Capturing the output in a buffer means that it can redirected to other functions such as email, or copied to a file as a cached representation of the content

What is Robocopy's "restartable" option?

Restartable mode (/Z) has to do with a partially-copied file. With this option, should the copy be interrupted while any particular file is partially copied, the next execution of robocopy can pick up where it left off rather than re-copying the entire file.

That option could be useful when copying very large files over a potentially unstable connection.

Backup mode (/B) has to do with how robocopy reads files from the source system. It allows the copying of files on which you might otherwise get an access denied error on either the file itself or while trying to copy the file's attributes/permissions. You do need to be running in an Administrator context or otherwise have backup rights to use this flag.

SSRS custom number format

am assuming that you want to know how to format numbers in SSRS

Just right click the TextBox on which you want to apply formatting, go to its expression.

suppose its expression is something like below


then do this




difference between the two is that former one would make 4 as 4 and later one would make 4 as 04.00

this should give you an idea.

also: you might have to convert your field into a numerical one. i.e.


so: 0 in format expression means, when no number is present, place a 0 there and # means when no number is present, leave it. Both of them works same when numbers are present ie. 45.6567 would be 45.65 for both of them:


if you want to apply variable formatting on the same column based on row values i.e. you want myField to have no formatting when it has no decimal value but formatting with double precision when it has decimal then you can do it through logic. (though you should not be doing so)

Go to the appropriate textbox and go to its expression and do this:

=IIF((Fields!myField.Value - CInt(Fields!myField.Value)) > 0, 
    Format(Fields!myField.Value, "##.##"),Fields!myField.Value)

so basically you are using IIF(condition, true,false) operator of SSRS, ur condition is to check whether the number has decimal value, if it has, you apply the formatting and if no, you let it as it is.

this should give you an idea, how to handle variable formatting.

How to call a method defined in an AngularJS directive?

A bit late, but this is a solution with the isolated scope and "events" to call a function in the directive. This solution is inspired by this SO post by satchmorun and adds a module and an API.

//Create module
var MapModule = angular.module('MapModule', []);

//Load dependency dynamically

Create an API to communicate with the directive. The addUpdateEvent adds an event to the event array and updateMap calls every event function.

MapModule.factory('MapApi', function () {
    return {
        events: [],

        addUpdateEvent: function (func) {

        updateMap: function () {
   (func) {

(Maybe you have to add functionality to remove event.)

In the directive set a reference to the MapAPI and add $scope.updateMap as an event when MapApi.updateMap is called.

app.directive('map', function () {
    return {
        restrict: 'E', 
        scope: {}, 
        templateUrl: '....',
        controller: function ($scope, $http, $attrs, MapApi) {

            $scope.api = MapApi;

            $scope.updateMap = function () {
                //Update the map 

            //Add event


In the "main" controller add a reference to the MapApi and just call MapApi.updateMap() to update the map.

app.controller('mainController', function ($scope, MapApi) {

    $scope.updateMapButtonClick = function() {

Write to CSV file and export it?

How to write to a file (easy search in Google) ... 1st Search Result

As far as creation of the file each time a user accesses the page ... each access will act on it's own behalf. You business case will dictate the behavior.

Case 1 - same file but does not change (this type of case can have multiple ways of being defined)

  • You would have logic that created the file when needed and only access the file if generation is not needed.

Case 2 - each user needs to generate their own file

  • You would decide how you identify each user, create a file for each user and access the file they are supposed to see ... this can easily merge with Case 1. Then you delete the file after serving the content or not if it requires persistence.

Case 3 - same file but generation required for each access

  • Use Case 2, this will cause a generation each time but clean up once accessed.

How to create a file in memory for user to download, but not through server?

Simple solution for HTML5 ready browsers...

function download(filename, text) {_x000D_
  var element = document.createElement('a');_x000D_
  element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));_x000D_
  element.setAttribute('download', filename);_x000D_
_x000D_ = 'none';_x000D_
form * {_x000D_
  display: block;_x000D_
  margin: 10px;_x000D_
<form onsubmit="download(this['name'].value, this['text'].value)">_x000D_
  <input type="text" name="name" value="test.txt">_x000D_
  <textarea name="text"></textarea>_x000D_
  <input type="submit" value="Download">_x000D_


download('test.txt', 'Hello world!');

Uncaught Error: SECURITY_ERR: DOM Exception 18 when I try to set a cookie

I had this issue when using the history API.

window.history.pushState(null, null, URL);

Even with a local server (localhost), you want to add 'http://' to your URL so that you have something similar to:


How to convert a Django QuerySet to a list

It is a little hard to follow what you are really trying to do. Your first statement looks like you may be fetching the same exact QuerySet of Answer objects twice. First via answer_set.answers.all() and then again via .filter(id__in=...). Double check in the shell and see if this will give you the list of answers you are looking for:

answers = answer_set.answers.all()

Once you have that cleaned up so it is a little easier for you (and others working on the code) to read you might want to look into .exclude() and the __in field lookup.

existing_question_answers = QuestionAnswer.objects.filter(...)

new_answers = answers.exclude(question_answer__in=existing_question_answers)

The above lookup might not sync up with your model definitions but it will probably get you close enough to finish the job yourself.

If you still need to get a list of id values then you want to play with .values_list(). In your case you will probably want to add the optional flat=True.

answers.values_list('id', flat=True)

Python: Passing variables between functions

You're just missing one critical step. You have to explicitly pass the return value in to the second function.

def main():
    l = defineAList()


def main():

Or (though you shouldn't do this! It might seem nice at first, but globals just cause you grief in the long run.):

l = []

def defineAList():
    global l

def main():
    global l

The function returns a value, but it doesn't create the symbol in any sort of global namespace as your code assumes. You have to actually capture the return value in the calling scope and then use it for subsequent operations.

Dropping Unique constraint from MySQL table

If you want to remove unique constraints from mysql database table, use alter table with drop index.


create table unique_constraints(unid int,activity_name varchar(100),CONSTRAINT activty_uqniue UNIQUE(activity_name),primary key (unid));

alter table unique_constraints drop index activty_uqniue;

Where activty_uqniue is UNIQUE constraint for activity_name column.

When to use CouchDB over MongoDB and vice versa

Very old question but it's on top of Google and I don't quite like the answers I see so here's my own.

There's much more to Couchdb than the ability to develop CouchApps. Most people use CouchDb in a classical 3-tiers web architecture.

In practice the deciding factor for most people will be the fact that MongoDb allows ad-hoc querying with a SQL like syntax while CouchDb doesn't (you've got to create map/reduce views which turns some people off even though creating these views is Rapid Application Development friendly - they have nothing to do with stored procedures).

To address points raised in the accepted answer : CouchDb has a great versionning system, but it doesn't mean that it is only suited (or more suited) for places where versionning is important. Also, couchdb is heavy-write friendly thanks to its append-only nature (writes operations return in no time while guaranteeing that no data will ever be lost).

One very important thing that is not mentioned by anyone is the fact that CouchDb relies on b-tree indexes. This means that whether you have 1 "row" or 20 billions, the querying time will always remain below 10ms. This is a game changer which makes CouchDb a low-latency and read-friendly database, and this really shouldn't be overlooked.

To be fair and exhaustive the advantage MongoDb has over CouchDb is tooling and marketing. They have first-class citizen tools for all major languages and platforms making the on-boarding easy and this added to their adhoc querying makes the transition from SQL even easier.

CouchDb doesn't have this level of tooling - even though there are many libraries available today - but CouchDb is exposed as an HTTP API and it is therefore quite easy to create a wrapper in your favorite language to talk with it. I personally like this approach as it avoids bloat and allows you to only take what you want (interface segregation principle).

So I'd say using one or the other is largely a matter of comfort and preference with their paradigms. CouchDb approach "just fits", for certain people, but if after learning about the database features (in the exhaustive official guide) you don't have your "hell yeah" moment, you should probably move on.

I'd discourage using CouchDb if you just want to use "the right tool for the right job". because you'll find out that you can't just use it that way and you'll end up being pissed and writing blog posts such as "Where are joins in CouchDb ?" and "Where is transaction management ?". Indeed Couchdb is - paradoxically - very transparent but at the same time requires a paradigm shift and a change in the way you approach problems to really shine (and really work).

But once you've done that it really pays off. I'd personally need very strong reasons or a major deal breaker on a project to choose another database, but so far I haven't met any.

How to load/reference a file as a File instance from the classpath

Try getting hold of a URL for your classpath resource:

URL url = this.getClass().getResource("/com/path/to/file.txt")

Then create a file using the constructor that accepts a URI:

File file = new File(url.toURI());

Initializing multiple variables to the same value in Java

Works for primitives and immutable classes like String, Wrapper classes Character, Byte.

int i=0,j=2   
String s1,s2  
s1 = s2 = "java rocks"

For mutable classes

Reference r1 = Reference r2 = Reference r3 = new Object();`  

Three references + one object are created. All references point to the same object and your program will misbehave.

calculate the mean for each column of a matrix in R

In case you have NA's:

sapply(data, mean, na.rm = T)      # Returns a vector (with names)   
lapply(data, mean, na.rm = T)      # Returns a list  

Remember that "mean" needs numeric data. If you have mixed class data, then use:

numdata<-data[sapply(data, is.numeric)]  
sapply(numdata, mean, na.rm = T)  # Returns a vector
lapply(numdata, mean, na.rm = T)  # Returns a list  

Generate a dummy-variable

What I normally do to work with this kind of dummy variables is:

(1) how do I generate a dummy variable for observation #10, i.e. for year 1957 (value = 1 at 1957 and zero otherwise)

data$factor_year_1 <- factor ( with ( data, ifelse ( ( year == 1957 ), 1 , 0 ) ) )

(2) how do I generate a dummy-variable which is zero before 1957 and takes the value 1 from 1957 and onwards to 2009?

data$factor_year_2 <- factor ( with ( data, ifelse ( ( year < 1957 ), 0 , 1 ) ) )

Then, I can introduce this factor as a dummy variable in my models. For example, to see whether there is a long-term trend in a varible y :

summary ( lm ( y ~ t,  data = data ) )

Hope this helps!

Visual Studio Expand/Collapse keyboard shortcuts

For collapse, you can try CTRL + M + O and expand using CTRL + M + P. This works in VS2008.

Printing leading 0's in C

printf("%05d", zipCode);

The 0 indicates what you are padding with and the 5 shows the width of the integer number.

Example 1: If you use "%02d" (useful for dates) this would only pad zeros for numbers in the ones column. E.g., 06 instead of 6.

Example 2: "%03d" would pad 2 zeros for one number in the ones column and pad 1 zero for a number in the tens column. E.g., number 7 padded to 007 and number 17 padded to 017.

How to set host_key_checking=false in ansible inventory file?

I could not use:

ansible_ssh_common_args='-o StrictHostKeyChecking=no'

in inventory file. It seems ansible does not consider this option in my case (ansible from pip in ubuntu 14.04)

I decided to use:

server ansible_host= ansible_ssh_common_args= '-o UserKnownHostsFile=/dev/null'

It helped me.

Also you could set this variable in group instead for each host:

ansible_ssh_common_args='-o UserKnownHostsFile=/dev/null'

writing integer values to a file using out.write()

any of these should work

outf.write("%s" % num)


print >> outf, num

Put a Delay in Javascript

If you're okay with ES2017, await is good:

const DEF_DELAY = 1000;

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms || DEF_DELAY));

await sleep(100);

Note that the await part needs to be in an async function:

//IIAFE (immediately invoked async function expression)
  //Do some stuff
  await sleep(100);
  //Do some more stuff

In Firebase, is there a way to get the number of children of a node without loading all the node data?

The code snippet you gave does indeed load the entire set of data and then counts it client-side, which can be very slow for large amounts of data.

Firebase doesn't currently have a way to count children without loading data, but we do plan to add it.

For now, one solution would be to maintain a counter of the number of children and update it every time you add a new child. You could use a transaction to count items, like in this code tracking upvodes:

var upvotesRef = new Firebase('');
upvotesRef.transaction(function (current_value) {
  return (current_value || 0) + 1;

For more info, see

UPDATE: Firebase recently released Cloud Functions. With Cloud Functions, you don't need to create your own Server. You can simply write JavaScript functions and upload it to Firebase. Firebase will be responsible for triggering functions whenever an event occurs.

If you want to count upvotes for example, you should create a structure similar to this one:

  "posts" : {
    "-JRHTHaIs-jNPLXOQivY" : {
      "upvotes" : {
      "userX" : true,
      "userY" : true,
      "userZ" : true,

And then write a javascript function to increase the upvotes_count when there is a new write to the upvotes node.

const functions = require('firebase-functions');
const admin = require('firebase-admin');

exports.countlikes = functions.database.ref('/posts/$postid/upvotes').onWrite(event => {

You can read the Documentation to know how to Get Started with Cloud Functions.

Also, another example of counting posts is here:

Update January 2018

The firebase docs have changed so instead of event we now have change and context.

The given example throws an error complaining that is undefined. This pattern seems to work better:

exports.countPrescriptions = functions.database.ref(`/prescriptions`).onWrite((change, context) => {
    const data = change.after.val();
    const count = Object.keys(data).length;
    return change.after.ref.child('_count').set(count);


Why is list initialization (using curly braces) better than the alternatives?

It only safer as long as you don't build with -Wno-narrowing like say Google does in Chromium. If you do, then it is LESS safe. Without that flag the only unsafe cases will be fixed by C++20 though.

Note: A) Curly brackets are safer because they don't allow narrowing. B) Curly brackers are less safe because they can bypass private or deleted constructors, and call explicit marked constructors implicitly.

Those two combined means they are safer if what is inside is primitive constants, but less safe if they are objects (though fixed in C++20)

Filter by Dates in SQL

WHERE dates BETWEEN (convert(datetime, '2012-12-12',110) AND (convert(datetime, '2012-12-12',110))

Protecting cells in Excel but allow these to be modified by VBA script

A basic but simple to understand answer:

Sub Example()
    Program logic...
End Sub

Android Studio Gradle Configuration with name 'default' not found

Yet another cause - I was trying to include a module in settings.gradle using

include ':MyModule'
project(':MyModule').projectDir = new File(settingsDir, '../../MyModule')

Only problem was, I had just imported the module from Eclipse an forgot to move the directory outside my application project, i.e. the path '../../MyModule' didn't exist.

Sending emails with Javascript

You can use this free service:

  1. Include the script:

<script src=""></script>

  1. Send an email using:
  "[email protected]",
  "[email protected]",
  "This is a subject",
  "this is the body",

How to create an array of 20 random bytes?

Java 7 introduced ThreadLocalRandom which is isolated to the current thread.

This is an another rendition of maerics's solution.

final byte[] bytes = new byte[20];

Check if a list contains an item in Ansible

Ansible has a version_compare filter since 1.6. You can do something like below in when conditional:

when: ansible_distribution_version | version_compare('12.04', '>=')

This will give you support for major & minor versions comparisons and you can compare versions using operators like:

<, lt, <=, le, >, gt, >=, ge, ==, =, eq, !=, <>, ne

You can find more information about this here: Ansible - Version comparison filters

Otherwise if you have really simple case you can use what @ProfHase85 suggested

How to set focus on input field?

This is also possible to use ngModelController. Working with 1.6+ (don't know with older versions).


<form name="myForm">
    <input type="text" name="myText" ng-model="myText">




N.B.: Depending of the context, you maybe have to wrap in a timeout function.

N.B.²: When using controllerAs, this is almost the same. Just replace name="myForm" with name="vm.myForm" and in JS, vm.myForm.myText.$$element.focus();.

MySQL: ERROR 1227 (42000): Access denied - Cannot CREATE USER

First thing to do is run this:


You will quickly see you were assigned the anonymous user to authenticate into mysql.

Instead of logging into mysql with


login like this:

mysql -uroot

By default, root@localhost has all rights and no password.

If you cannot login as root without a password, do the following:

Step 01) Add the two options in the mysqld section of my.ini:


Step 02) Restart mysql

net stop mysql
<wait 10 seconds>
net start mysql

Step 03) Connect to mysql


Step 04) Create a password from root@localhost

UPDATE mysql.user SET password=password('whateverpasswordyoulike')
WHERE user='root' AND host='localhost';

Step 05) Restart mysql

net stop mysql
<wait 10 seconds>
net start mysql

Step 06) Login as root with password

mysql -u root -p

You should be good from there.

CAVEAT: Please remove anonymous users !!!

CodeIgniter query: How to move a column value to another column in the same row and save the current time in the original column?

Yes, this is possible and I would like to provide a slight alternative to Rajeev's answer that does not pass a php-generated datetime formatted string to the query.

The important distinction about how to declare the values to be SET in the UPDATE query is that they must not be quoted as literal strings.

To prevent CodeIgniter from doing this "favor" automatically, use the set() method with a third parameter of false.

$userId = 444;
$this->db->set('Last', 'Current', false);
$this->db->set('Current', 'NOW()', false);
$this->db->where('Id', $userId);
// return $this->db->get_compiled_update('Login');  // uncomment to see the rendered query
return $this->db->affected_rows();  // this is expected to return the integer: 1

The generated query (depending on your database adapter) would be like this:

UPDATE `Login` SET Last = Current, Current = NOW() WHERE `Id` = 444

Demonstrated proof that the query works:

In this case, Last and Current ARE MySQL Keywords, but they are not Reserved Keywords, so they don't need to be backtick-wrapped.

If your precise query needs to have properly quoted identifiers (table/column names), then there is always protectIdentifiers().

How do I insert a JPEG image into a python Tkinter window?

import tkinter as tk
from tkinter import ttk
from PIL import Image,  ImageTk
win = tk. Tk()
image1 = Image. open("Aoran. jpg")
image2 =  ImageTk. PhotoImage(image1)
image_label = ttk. Label(win , image =.image2) = 0 , y = 0)

How to export all collections in MongoDB?

if you want to use mongoexport and mongoimport to export/import each collection from database, I think this utility can be helpful for you. I've used similar utility couple of times;


    cat << EOF
    usage: $0 [options] dbname

        -h      Show this help.
        -l      Load instead of export
        -u      Mongo username
        -p      Mongo password
        -H      Mongo host string (ex. localhost:27017)

while getopts "hlu:p:H:" opt; do

    case $opt in 
            echo "Invalid option $opt"
            exit 1

shift $(($MAXOPTIND-1))

if [ -z "$1" ]; then
    echo "Usage: export-mongo [opts] <dbname>"
    exit 1

if [ -z "$HOST" ]; then

if [ -n "$USERNAME" ]; then
if [ -n "$PASSWORD" ]; then

echo "*************************** Mongo Export ************************"
echo "**** Host:      $HOST"
echo "**** Database:  $DB"
echo "**** Username:  $USERNAME"
echo "**** Password:  $PASSWORD"
echo "**** Loading:   $LOADING"
echo "*****************************************************************"

if $LOADING ; then
    echo "Loading into $CONN"
    tar -xzf $DB.tar.gz
    pushd $DB >/dev/null

    for path in *.json; do
        echo "Loading into $DB/$collection from $path"
        mongoimport $ARGS -d $DB -c $collection $path

    popd >/dev/null
    rm -rf $DB
    DATABASE_COLLECTIONS=$(mongo $CONN $ARGS --quiet --eval 'db.getCollectionNames()' | sed 's/,/ /g')

    mkdir /tmp/$DB
    pushd /tmp/$DB 2>/dev/null

    for collection in $DATABASE_COLLECTIONS; do
        mongoexport --host $HOST -u $USERNAME -p $PASSWORD -db $DB -c $collection --jsonArray -o $collection.json >/dev/null

    pushd /tmp 2>/dev/null
    tar -czf "$DB.tar.gz" $DB 2>/dev/null
    popd 2>/dev/null
    popd 2>/dev/null
    mv /tmp/$DB.tar.gz ./ 2>/dev/null
    rm -rf /tmp/$DB 2>/dev/null

Send POST parameters with MultipartFormData using Alamofire, in iOS Swift

Swift 5, update @Ankush's Alamofire Code to

     var fullUrl = "" // for example

           Alamofire.upload(multipartFormData: { (multipartFormData) in
                multipartFormData.append( imagePathUrl! , withName: "photo")
                multipartFormData.append( videoPathUrl!,  withName: "video")
                multipartFormData.append( .utf8, allowLossyConversion: false)!, withName: "authKey")
                multipartFormData.append("16".data(using: .utf8, allowLossyConversion: false)!, withName: "idUserChallenge")
                multipartFormData.append("111".data(using: .utf8, allowLossyConversion: false)!, withName: "authKey")
                multipartFormData.append("comment".data(using: .utf8, allowLossyConversion: false)!, withName: "comment")
                multipartFormData.append("0.00".data(using: .utf8, allowLossyConversion: false)!, withName: "latitude")
                multipartFormData.append("0.00".data(using: .utf8, allowLossyConversion: false)!, withName: "longitude")
                multipartFormData.append("India".data(using: .utf8, allowLossyConversion: false)!, withName: "location")

            }, to: fullUrl, method: .post) { (encodingResult) in
                switch encodingResult {
                case .success(request: let upload, streamingFromDisk: _, streamFileURL: _):
                    upload.responseJSON { (response) in   // do sth     }
                case .failure(let encodingError):

Get Hours and Minutes (HH:MM) from date

If you want to display 24 hours format use:


and to display 12 hours format use:


Formatting PowerShell Get-Date inside string

"This is my string with date in specified format $($theDate.ToString('u'))"


"This is my string with date in specified format $(Get-Date -format 'u')"

The sub-expression ($(...)) can include arbitrary expressions calls.

MSDN Documents both standard and custom DateTime format strings.

What is the suggested way to install brew, node.js, io.js, nvm, npm on OS X?

I agree with noa -- if you need to have multiple versions of node, io.js then brew is not the appropriate solution.

You can help beta-test io.js support in nvm:

If you just want io.js and are not switching versions, then you can install the binary distribution of io.js from ; that includes npm and you will not need nvm if you are not switching versions.

Remember to update npm after installing: sudo npm install -g npm@latest

How do I control how Emacs makes backup files?

You can disable them altogether by

(setq make-backup-files nil)

How to create a table from select query result in SQL Server 2008

Please be careful, MSSQL: "SELECT * INTO NewTable FROM OldTable"

is not always the same as MYSQL: "create table temp AS select.."

I think that there are occasions when this (in MSSQL) does not guarantee that all the fields in the new table are of the same type as the old.

For example :

create table oldTable (field1 varchar(10), field2 integer, field3 float)
insert into oldTable (field1,field2,field3) values ('1', 1, 1)
select top 1 * into newTable from oldTable

does not always yield:

create table newTable (field1 varchar(10), field2 integer, field3 float)

but may be:

create table newTable (field1 varchar(10), field2 integer, field3 integer)

SOAP-UI - How to pass xml inside parameter

NOTE: This one is just an alternative for the previous provided .NET framework 3.5 and above

You can send it as raw xml

<test>or like this</test>

If you declare the paramater2 as XElement data type

Use child_process.execSync but keep output in console

Unless you redirect stdout and stderr as the accepted answer suggests, this is not possible with execSync or spawnSync. Without redirecting stdout and stderr those commands only return stdout and stderr when the command is completed.

To do this without redirecting stdout and stderr, you are going to need to use spawn to do this but it's pretty straight forward:

var spawn = require('child_process').spawn;

//kick off process of listing files
var child = spawn('ls', ['-l', '/']);

//spit stdout to screen
child.stdout.on('data', function (data) {   process.stdout.write(data.toString());  });

//spit stderr to screen
child.stderr.on('data', function (data) {   process.stdout.write(data.toString());  });

child.on('close', function (code) { 
    console.log("Finished with code " + code);

I used an ls command that recursively lists files so that you can test it quickly. Spawn takes as first argument the executable name you are trying to run and as it's second argument it takes an array of strings representing each parameter you want to pass to that executable.

However, if you are set on using execSync and can't redirect stdout or stderr for some reason, you can open up another terminal like xterm and pass it a command like so:

var execSync = require('child_process').execSync;

execSync("xterm -title RecursiveFileListing -e ls -latkR /");

This will allow you to see what your command is doing in the new terminal but still have the synchronous call.

Gson: How to exclude specific fields from Serialization without annotations

After reading all available answers I found out, that most flexible, in my case, was to use custom @Exclude annotation. So, I implemented simple strategy for this (I didn't want to mark all fields using @Expose nor I wanted to use transient which conflicted with in app Serializable serialization) :


public @interface Exclude {


public class AnnotationExclusionStrategy implements ExclusionStrategy {

    public boolean shouldSkipField(FieldAttributes f) {
        return f.getAnnotation(Exclude.class) != null;

    public boolean shouldSkipClass(Class<?> clazz) {
        return false;


new GsonBuilder().setExclusionStrategies(new AnnotationExclusionStrategy()).create();

How to copy a directory structure but only include certain files (using windows batch files)

To do this with drag and drop use winzip there's a dir structure preserve option. Simply create a new .zip at the directory level which will be your root and drag files in.

How to remove the first Item from a list?

If you are working with numpy you need to use the delete method:

import numpy as np

a = np.array([1, 2, 3, 4, 5])

a = np.delete(a, 0)

print(a) # [2 3 4 5]

How to insert multiple rows from a single query using eloquent/fluent

using Eloquent

$data = array(
    array('user_id'=>'Coder 1', 'subject_id'=> 4096),
    array('user_id'=>'Coder 2', 'subject_id'=> 2048),


Code for best fit straight line of a scatter plot in python

You can use numpy's polyfit. I use the following (you can safely remove the bit about coefficient of determination and error bounds, I just think it looks nice):


import numpy as np
import matplotlib.pyplot as plt
import csv

with open("example.csv", "r") as f:
    data = [row for row in csv.reader(f)]
    xd = [float(row[0]) for row in data]
    yd = [float(row[1]) for row in data]

# sort the data
reorder = sorted(range(len(xd)), key = lambda ii: xd[ii])
xd = [xd[ii] for ii in reorder]
yd = [yd[ii] for ii in reorder]

# make the scatter plot
plt.scatter(xd, yd, s=30, alpha=0.15, marker='o')

# determine best fit line
par = np.polyfit(xd, yd, 1, full=True)

xl = [min(xd), max(xd)]
yl = [slope*xx + intercept  for xx in xl]

# coefficient of determination, plot text
variance = np.var(yd)
residuals = np.var([(slope*xx + intercept - yy)  for xx,yy in zip(xd,yd)])
Rsqr = np.round(1-residuals/variance, decimals=2)
plt.text(.9*max(xd)+.1*min(xd),.9*max(yd)+.1*min(yd),'$R^2 = %0.2f$'% Rsqr, fontsize=30)

plt.xlabel("X Description")
plt.ylabel("Y Description")

# error bounds
yerr = [abs(slope*xx + intercept - yy)  for xx,yy in zip(xd,yd)]
par = np.polyfit(xd, yerr, 2, full=True)

yerrUpper = [(xx*slope+intercept)+(par[0][0]*xx**2 + par[0][1]*xx + par[0][2]) for xx,yy in zip(xd,yd)]
yerrLower = [(xx*slope+intercept)-(par[0][0]*xx**2 + par[0][1]*xx + par[0][2]) for xx,yy in zip(xd,yd)]

plt.plot(xl, yl, '-r')
plt.plot(xd, yerrLower, '--r')
plt.plot(xd, yerrUpper, '--r')

add string to String array

First, this code here,

string [] scripts = new String [] ("test3","test4","test5");

should be

String[] scripts = new String [] {"test3","test4","test5"};

Please read this tutorial on Arrays


Arrays are fixed size, so you can't add new Strings to above array. You may override existing values

scripts[0] = string1;


Create array with size then keep on adding elements till it is full.

If you want resizable arrays, consider using ArrayList.

JavaScript get element by name


How to get the concrete class name as a string?



>>> class A():
>>> a = A()
>>> a.__class__.__name__

Jquery in React is not defined

Add "ref" to h1 tag :

<h1 ref="source">Hey there.</h1>

const { source } = this.props; change to const { source } = this.refs;

Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported for @RequestBody MultiValueMap

It seems that now you can just mark the method parameter with @RequestParam and it will do the job for you.

@PostMapping( "some/request/path" )
public void someControllerMethod( @RequestParam Map<String, String> body ) {
  //work with Map