Programs & Examples On #Video gallery

Redirecting from cshtml page

Would be safer to do this.

@{ Response.Redirect("~/Account/LogIn?returnUrl=Products");}

So the controller for that action runs as well, to populate any model the view needs.

Redirect from a view to another view

Although as @Satpal mentioned, I do recommend you do the redirecting on your controller.

adding line break

Give this a try.

        FirmNames = String.Join(", \n", FirmNameList);

Importing PNG files into Numpy?

If you are loading images, you are likely going to be working with one or both of matplotlib and opencv to manipulate and view the images.

For this reason, I tend to use their image readers and append those to lists, from which I make a NumPy array.

import os
import matplotlib.pyplot as plt
import cv2
import numpy as np

# Get the file paths
im_files = os.listdir('path/to/files/')

# imagine we only want to load PNG files (or JPEG or whatever...)
EXTENSION = '.png'

# Load using matplotlib
images_plt = [plt.imread(f) for f in im_files if f.endswith(EXTENSION)]
# convert your lists into a numpy array of size (N, H, W, C)
images = np.array(images_plt)

# Load using opencv
images_cv = [cv2.imread(f) for f in im_files if f.endswith(EXTENSION)]
# convert your lists into a numpy array of size (N, C, H, W)
images = np.array(images_cv)

The only difference to be aware of is the following:

  • opencv loads channels first
  • matplotlib loads channels last.

So a single image that is 256*256 in size would produce matrices of size (3, 256, 256) with opencv and (256, 256, 3) using matplotlib.

getResourceAsStream() is always returning null

Instead of

InputStream fstream = this.getClass().getResourceAsStream("abc.txt"); 


InputStream fstream = this.getClass().getClassLoader().getResourceAsStream("abc.txt");

In this way it will look from the root, not from the path of the current invoking class

CSS On hover show another element

You can use axe selectors for this.

There are two approaches:

1. Immediate Parent axe Selector (<)

#a:hover < #content + #b

This axe style rule will select #b, which is the immediate sibling of #content, which is the immediate parent of #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);

#a:hover < #content + #b {
display: inline-block;
<div id="content">
<div id="a">Hover me</div>

<div id="b">Show me</div>

<script src=""></script>

2. Remote Element axe Selector (\)

#a:hover \ #b

This axe style rule will select #b, which is present in the same document as #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);

#a:hover \ #b {
display: inline-block;
<div id="content">
<div id="a">Hover me</div>

<div id="b">Show me</div>

<script src=""></script>

How to compile .c file with OpenSSL includes?

Your include paths indicate that you should be compiling against the system's OpenSSL installation. You shouldn't have the .h files in your package directory - it should be picking them up from /usr/include/openssl.

The plain OpenSSL package (libssl) doesn't include the .h files - you need to install the development package as well. This is named libssl-dev on Debian, Ubuntu and similar distributions, and libssl-devel on CentOS, Fedora, Red Hat and similar.

How can I format my grep output to show line numbers at the end of the line, and also the hit count?

or in perl (for completeness...):

perl -npe 'chomp; /null/ and print "$_ - Line number : $.\n" and $i++;$_="";END{print "Total null count : $i\n"}'

How to copy the first few lines of a giant file, and add a line of text at the end of it using some Linux commands?

The head command can get the first n lines. Variations are:

head -7 file
head -n 7 file
head -7l file

which will get the first 7 lines of the file called "file". The command to use depends on your version of head. Linux will work with the first one.

To append lines to the end of the same file, use:

echo 'first line to add' >>file
echo 'second line to add' >>file
echo 'third line to add' >>file


echo 'first line to add
second line to add
third line to add' >>file

to do it in one hit.

So, tying these two ideas together, if you wanted to get the first 10 lines of the input.txt file to output.txt and append a line with five "=" characters, you could use something like:

( head -10 input.txt ; echo '=====' ) > output.txt

In this case, we do both operations in a sub-shell so as to consolidate the output streams into one, which is then used to create or overwrite the output file.

Use LIKE %..% with field values in MySQL

  SELECT t1.a, t2.b
  FROM t1
  JOIN t2 ON t1.a LIKE '%'+t2.b +'%'

because the last answer not work

fatal error LNK1104: cannot open file 'libboost_system-vc110-mt-gd-1_51.lib'

b2 -j%cores% toolset=%msvcver% address-model=64 architecture=x86 link=static threading=multi runtime-link=shared --build-type=minimal stage --stagedir=stage/x64

Properties ? Linker ? General ? Additional Library Directories $(BOOST)\stage\x64\lib

Difference between Java SE/EE/ME?

Yes, Java SE is where to start. All the tasks you mention can be handled with it.

Java ME is the Mobile Edition, and EE is Enterprise Edition; these are specialized / extended versions of Standard Edition.

how to download file in react js

Triggering browser download from front-end is not reliable.

What you should do is, create an endpoint that when called, will provide the correct response headers, thus triggering the browser download.

Front-end code can only do so much. The 'download' attribute for example, might just open the file in a new tab depending on the browser.

The response headers you need to look at are probably Content-Type and Content-Disposition. You should check this answer for more detailed explanation.

How to convert a String to Bytearray

In C# running this

UnicodeEncoding encoding = new UnicodeEncoding();
byte[] bytes = encoding.GetBytes("Hello");

Will create an array with


byte array

For a character which the code is greater than 255 it will look like this

byte array

If you want a very similar behavior in JavaScript you can do this (v2 is a bit more robust solution, while the original version will only work for 0x00 ~ 0xff)

var str = "Hello?";_x000D_
var bytes = []; // char codes_x000D_
var bytesv2 = []; // char codes_x000D_
for (var i = 0; i < str.length; ++i) {_x000D_
  var code = str.charCodeAt(i);_x000D_
  bytes = bytes.concat([code]);_x000D_
  bytesv2 = bytesv2.concat([code & 0xff, code / 256 >>> 0]);_x000D_
// 72, 101, 108, 108, 111, 31452_x000D_
console.log('bytes', bytes.join(', '));_x000D_
// 72, 0, 101, 0, 108, 0, 108, 0, 111, 0, 220, 122_x000D_
console.log('bytesv2', bytesv2.join(', '));

What does DIM stand for in Visual Basic and BASIC?

It's short for Dimension, as it was originally used in BASIC to specify the size of arrays.

DIM — (short for dimension) define the size of arrays


A part of the original BASIC compiler source code, where it would jump when finding a DIM command, in which you can clearly see the original intention for the keyword:

       SUB N3
       STA RX01
       STA 3
       LDA S        3
       CAB N36              CHECK FOR $ ARRAY
       BRU *+7              NOT $


Later on it came to be used to declare all kinds of variables, when the possibility to specify the type for variables was added in more recent implementations.

Reading From A Text File - Batch

Your code "for /f "tokens=* delims=" %%x in (a.txt) do echo %%x" will work on most Windows Operating Systems unless you have modified commands.

So you could instead "cd" into the directory to read from before executing the "for /f" command to follow out the string. For instance if the file "a.txt" is located at C:\documents and settings\%USERNAME%\desktop\a.txt then you'd use the following.

cd "C:\documents and settings\%USERNAME%\desktop"
for /f "tokens=* delims=" %%x in (a.txt) do echo %%x
pause >nul

But since this doesn't work on your computer for x reason there is an easier and more efficient way of doing this. Using the "type" command.

@echo off
color a
cd "C:\documents and settings\%USERNAME%\desktop"
type a.txt
pause >nul

Or if you'd like them to select the file from which to write in the batch you could do the following.

@echo off
color a
echo Choose the file that you want to read.
set file=
set /p file=File:
echo Reading from %file%
type %file%
set re=
set /p re=Y/N?:
if %re%==Y goto :A
if %re%==y goto :A

How can I right-align text in a DataGridView column?

I know this is old, but for those surfing this question, the answer by MUG4N will align all columns that use the same defaultcellstyle. I'm not using autogeneratecolumns so that is not acceptable. Instead I used:

e.Column.DefaultCellStyle = new DataGridViewCellStyle(e.Column.DefaultCellStyle);
e.Column.DefaultCellStyle.Alignment = DataGridViewContentAlignment.MiddleRight;

In this case e is from:

Grd_ColumnAdded(object sender, DataGridViewColumnEventArgs e)  

Undefined function mysql_connect()

In php.ini file

change this




Eclipse: How do I add the javax.servlet package to a project?

Go to


include JAR


For me it worked

How do I profile memory usage in Python?

Python 3.4 includes a new module: tracemalloc. It provides detailed statistics about which code is allocating the most memory. Here's an example that displays the top three lines allocating memory.

from collections import Counter
import linecache
import os
import tracemalloc

def display_top(snapshot, key_type='lineno', limit=3):
    snapshot = snapshot.filter_traces((
        tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
        tracemalloc.Filter(False, "<unknown>"),
    top_stats = snapshot.statistics(key_type)

    print("Top %s lines" % limit)
    for index, stat in enumerate(top_stats[:limit], 1):
        frame = stat.traceback[0]
        # replace "/path/to/module/" with "module/"
        filename = os.sep.join(frame.filename.split(os.sep)[-2:])
        print("#%s: %s:%s: %.1f KiB"
              % (index, filename, frame.lineno, stat.size / 1024))
        line = linecache.getline(frame.filename, frame.lineno).strip()
        if line:
            print('    %s' % line)

    other = top_stats[limit:]
    if other:
        size = sum(stat.size for stat in other)
        print("%s other: %.1f KiB" % (len(other), size / 1024))
    total = sum(stat.size for stat in top_stats)
    print("Total allocated size: %.1f KiB" % (total / 1024))


counts = Counter()
fname = '/usr/share/dict/american-english'
with open(fname) as words:
    words = list(words)
    for word in words:
        prefix = word[:3]
        counts[prefix] += 1
print('Top prefixes:', counts.most_common(3))

snapshot = tracemalloc.take_snapshot()

And here are the results:

Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
Top 3 lines
#1: scratches/ 6527.1 KiB
    words = list(words)
#2: scratches/ 247.7 KiB
    prefix = word[:3]
#3: scratches/ 193.0 KiB
    counts[prefix] += 1
4 other: 4.3 KiB
Total allocated size: 6972.1 KiB

When is a memory leak not a leak?

That example is great when the memory is still being held at the end of the calculation, but sometimes you have code that allocates a lot of memory and then releases it all. It's not technically a memory leak, but it's using more memory than you think it should. How can you track memory usage when it all gets released? If it's your code, you can probably add some debugging code to take snapshots while it's running. If not, you can start a background thread to monitor memory usage while the main thread runs.

Here's the previous example where the code has all been moved into the count_prefixes() function. When that function returns, all the memory is released. I also added some sleep() calls to simulate a long-running calculation.

from collections import Counter
import linecache
import os
import tracemalloc
from time import sleep

def count_prefixes():
    sleep(2)  # Start up time.
    counts = Counter()
    fname = '/usr/share/dict/american-english'
    with open(fname) as words:
        words = list(words)
        for word in words:
            prefix = word[:3]
            counts[prefix] += 1
    most_common = counts.most_common(3)
    sleep(3)  # Shut down time.
    return most_common

def main():

    most_common = count_prefixes()
    print('Top prefixes:', most_common)

    snapshot = tracemalloc.take_snapshot()

def display_top(snapshot, key_type='lineno', limit=3):
    snapshot = snapshot.filter_traces((
        tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
        tracemalloc.Filter(False, "<unknown>"),
    top_stats = snapshot.statistics(key_type)

    print("Top %s lines" % limit)
    for index, stat in enumerate(top_stats[:limit], 1):
        frame = stat.traceback[0]
        # replace "/path/to/module/" with "module/"
        filename = os.sep.join(frame.filename.split(os.sep)[-2:])
        print("#%s: %s:%s: %.1f KiB"
              % (index, filename, frame.lineno, stat.size / 1024))
        line = linecache.getline(frame.filename, frame.lineno).strip()
        if line:
            print('    %s' % line)

    other = top_stats[limit:]
    if other:
        size = sum(stat.size for stat in other)
        print("%s other: %.1f KiB" % (len(other), size / 1024))
    total = sum(stat.size for stat in top_stats)
    print("Total allocated size: %.1f KiB" % (total / 1024))


When I run that version, the memory usage has gone from 6MB down to 4KB, because the function released all its memory when it finished.

Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
Top 3 lines
#1: collections/ 0.7 KiB
    self.update(*args, **kwds)
#2: collections/ 0.6 KiB
    return _heapq.nlargest(n, self.items(), key=_itemgetter(1))
#3: python3.6/ 0.5 KiB
    result = [(key(elem), i, elem) for i, elem in zip(range(0, -n, -1), it)]
10 other: 2.2 KiB
Total allocated size: 4.0 KiB

Now here's a version inspired by another answer that starts a second thread to monitor memory usage.

from collections import Counter
import linecache
import os
import tracemalloc
from datetime import datetime
from queue import Queue, Empty
from resource import getrusage, RUSAGE_SELF
from threading import Thread
from time import sleep

def memory_monitor(command_queue: Queue, poll_interval=1):
    old_max = 0
    snapshot = None
    while True:
            if snapshot is not None:

        except Empty:
            max_rss = getrusage(RUSAGE_SELF).ru_maxrss
            if max_rss > old_max:
                old_max = max_rss
                snapshot = tracemalloc.take_snapshot()
                print(, 'max RSS', max_rss)

def count_prefixes():
    sleep(2)  # Start up time.
    counts = Counter()
    fname = '/usr/share/dict/american-english'
    with open(fname) as words:
        words = list(words)
        for word in words:
            prefix = word[:3]
            counts[prefix] += 1
    most_common = counts.most_common(3)
    sleep(3)  # Shut down time.
    return most_common

def main():
    queue = Queue()
    poll_interval = 0.1
    monitor_thread = Thread(target=memory_monitor, args=(queue, poll_interval))
        most_common = count_prefixes()
        print('Top prefixes:', most_common)

def display_top(snapshot, key_type='lineno', limit=3):
    snapshot = snapshot.filter_traces((
        tracemalloc.Filter(False, "<frozen importlib._bootstrap>"),
        tracemalloc.Filter(False, "<unknown>"),
    top_stats = snapshot.statistics(key_type)

    print("Top %s lines" % limit)
    for index, stat in enumerate(top_stats[:limit], 1):
        frame = stat.traceback[0]
        # replace "/path/to/module/" with "module/"
        filename = os.sep.join(frame.filename.split(os.sep)[-2:])
        print("#%s: %s:%s: %.1f KiB"
              % (index, filename, frame.lineno, stat.size / 1024))
        line = linecache.getline(frame.filename, frame.lineno).strip()
        if line:
            print('    %s' % line)

    other = top_stats[limit:]
    if other:
        size = sum(stat.size for stat in other)
        print("%s other: %.1f KiB" % (len(other), size / 1024))
    total = sum(stat.size for stat in top_stats)
    print("Total allocated size: %.1f KiB" % (total / 1024))


The resource module lets you check the current memory usage, and save the snapshot from the peak memory usage. The queue lets the main thread tell the memory monitor thread when to print its report and shut down. When it runs, it shows the memory being used by the list() call:

2018-05-29 10:34:34.441334 max RSS 10188
2018-05-29 10:34:36.475707 max RSS 23588
2018-05-29 10:34:36.616524 max RSS 38104
2018-05-29 10:34:36.772978 max RSS 45924
2018-05-29 10:34:36.929688 max RSS 46824
2018-05-29 10:34:37.087554 max RSS 46852
Top prefixes: [('con', 1220), ('dis', 1002), ('pro', 809)]
2018-05-29 10:34:56.281262
Top 3 lines
#1: scratches/ 6527.0 KiB
    words = list(words)
#2: scratches/ 16.4 KiB
    prefix = word[:3]
#3: scratches/ 10.1 KiB
    counts[prefix] += 1
19 other: 10.8 KiB
Total allocated size: 6564.3 KiB

If you're on Linux, you may find /proc/self/statm more useful than the resource module.

How to submit a form with JavaScript by clicking a link?

here's the best solution to your question: inside the form you have these code:

<li><a href="#">Singup</a></li>
<button type="submit" id="haha"></button>

in the CSS file, do this:

  display: none;

in JS you do this:


There you go.

Xcode 5.1 - No architectures to compile for (ONLY_ACTIVE_ARCH=YES, active arch=x86_64, VALID_ARCHS=i386)

To avoid having "pod install" reset only_active_arch for debug each time it's run, you can add the following to your pod file

# Append to your Podfile
post_install do |installer_representation|
    installer_representation.project.targets.each do |target|
        target.build_configurations.each do |config|
            config.build_settings['ONLY_ACTIVE_ARCH'] = 'NO'

How to return a class object by reference in C++?

You're probably returning an object that's on the stack. That is, return_Object() probably looks like this:

Object& return_Object()
    Object object_to_return;
    // ... do stuff ...

    return object_to_return;

If this is what you're doing, you're out of luck - object_to_return has gone out of scope and been destructed at the end of return_Object, so myObject refers to a non-existent object. You either need to return by value, or return an Object declared in a wider scope or newed onto the heap.

Maven Out of Memory Build Failure

_JAVA_OPTIONS="-Xmx3G" mvn clean install

How to change the font and font size of an HTML input tag?

<input type ="text" id="txtComputer">



How to delete a workspace in Perforce (using p4v)?

From the "View" menu, select "Workspaces". You'll see all of the workspaces you've created. Select the workspaces you want to delete and click "Edit" -> "Delete Workspace", or right-click and select "Delete Workspace". If the workspace is "locked" to prevent changes, you'll get an error message.

To unlock the workspace, click "Edit" (or right-click and click "Edit Workspace") to pull up the workspace editor, uncheck the "locked" checkbox, and save your changes. You can delete the workspace once it's unlocked.

In my experience, the workspace will continue to be shown in the drop-down list until you click on it, at which point p4v will figure out you've deleted it and remove it from the list.

Best way to select random rows PostgreSQL

Given your specifications (plus additional info in the comments),

  • You have a numeric ID column (integer numbers) with only few (or moderately few) gaps.
  • Obviously no or few write operations.
  • Your ID column has to be indexed! A primary key serves nicely.

The query below does not need a sequential scan of the big table, only an index scan.

First, get estimates for the main query:

SELECT count(*) AS ct              -- optional
     , min(id)  AS min_id
     , max(id)  AS max_id
     , max(id) - min(id) AS id_span
FROM   big;

The only possibly expensive part is the count(*) (for huge tables). Given above specifications, you don't need it. An estimate will do just fine, available at almost no cost (detailed explanation here):

SELECT reltuples AS ct FROM pg_class WHERE oid = 'schema_name.big'::regclass;

As long as ct isn't much smaller than id_span, the query will outperform other approaches.

WITH params AS (
    SELECT 1       AS min_id           -- minimum id <= current min id
         , 5100000 AS id_span          -- rounded up. (max_id - min_id + buffer)
    SELECT p.min_id + trunc(random() * p.id_span)::integer AS id
    FROM   params p
          ,generate_series(1, 1100) g  -- 1000 + buffer
    GROUP  BY 1                        -- trim duplicates
    ) r
JOIN   big USING (id)
LIMIT  1000;                           -- trim surplus
  • Generate random numbers in the id space. You have "few gaps", so add 10 % (enough to easily cover the blanks) to the number of rows to retrieve.

  • Each id can be picked multiple times by chance (though very unlikely with a big id space), so group the generated numbers (or use DISTINCT).

  • Join the ids to the big table. This should be very fast with the index in place.

  • Finally trim surplus ids that have not been eaten by dupes and gaps. Every row has a completely equal chance to be picked.

Short version

You can simplify this query. The CTE in the query above is just for educational purposes:

    SELECT DISTINCT 1 + trunc(random() * 5100000)::integer AS id
    FROM   generate_series(1, 1100) g
    ) r
JOIN   big USING (id)
LIMIT  1000;

Refine with rCTE

Especially if you are not so sure about gaps and estimates.

WITH RECURSIVE random_pick AS (
   FROM  (
      SELECT 1 + trunc(random() * 5100000)::int AS id
      FROM   generate_series(1, 1030)  -- 1000 + few percent - adapt to your needs
      LIMIT  1030                      -- hint for query planner
      ) r
   JOIN   big b USING (id)             -- eliminate miss

   UNION                               -- eliminate dupe
   SELECT b.*
   FROM  (
      SELECT 1 + trunc(random() * 5100000)::int AS id
      FROM   random_pick r             -- plus 3 percent - adapt to your needs
      LIMIT  999                       -- less than 1000, hint for query planner
      ) r
   JOIN   big b USING (id)             -- eliminate miss
FROM   random_pick
LIMIT  1000;  -- actual limit

We can work with a smaller surplus in the base query. If there are too many gaps so we don't find enough rows in the first iteration, the rCTE continues to iterate with the recursive term. We still need relatively few gaps in the ID space or the recursion may run dry before the limit is reached - or we have to start with a large enough buffer which defies the purpose of optimizing performance.

Duplicates are eliminated by the UNION in the rCTE.

The outer LIMIT makes the CTE stop as soon as we have enough rows.

This query is carefully drafted to use the available index, generate actually random rows and not stop until we fulfill the limit (unless the recursion runs dry). There are a number of pitfalls here if you are going to rewrite it.

Wrap into function

For repeated use with varying parameters:

CREATE OR REPLACE FUNCTION f_random_sample(_limit int = 1000, _gaps real = 1.03)
   _surplus  int := _limit * _gaps;
   _estimate int := (           -- get current estimate from system
      SELECT c.reltuples * _gaps
      FROM   pg_class c
      WHERE  c.oid = 'big'::regclass);

   WITH RECURSIVE random_pick AS (
      SELECT *
      FROM  (
         SELECT 1 + trunc(random() * _estimate)::int
         FROM   generate_series(1, _surplus) g
         LIMIT  _surplus           -- hint for query planner
         ) r (id)
      JOIN   big USING (id)        -- eliminate misses

      UNION                        -- eliminate dupes
      SELECT *
      FROM  (
         SELECT 1 + trunc(random() * _estimate)::int
         FROM   random_pick        -- just to make it recursive
         LIMIT  _limit             -- hint for query planner
         ) r (id)
      JOIN   big USING (id)        -- eliminate misses
   FROM   random_pick
   LIMIT  _limit;
$func$  LANGUAGE plpgsql VOLATILE ROWS 1000;


SELECT * FROM f_random_sample();
SELECT * FROM f_random_sample(500, 1.05);

You could even make this generic to work for any table: Take the name of the PK column and the table as polymorphic type and use EXECUTE ... But that's beyond the scope of this question. See:

Possible alternative

IF your requirements allow identical sets for repeated calls (and we are talking about repeated calls) I would consider a materialized view. Execute above query once and write the result to a table. Users get a quasi random selection at lightening speed. Refresh your random pick at intervals or events of your choosing.

Postgres 9.5 introduces TABLESAMPLE SYSTEM (n)

Where n is a percentage. The manual:

The BERNOULLI and SYSTEM sampling methods each accept a single argument which is the fraction of the table to sample, expressed as a percentage between 0 and 100. This argument can be any real-valued expression.

Bold emphasis mine. It's very fast, but the result is not exactly random. The manual again:

The SYSTEM method is significantly faster than the BERNOULLI method when small sampling percentages are specified, but it may return a less-random sample of the table as a result of clustering effects.

The number of rows returned can vary wildly. For our example, to get roughly 1000 rows:

SELECT * FROM big TABLESAMPLE SYSTEM ((1000 * 100) / 5100000.0);


Or install the additional module tsm_system_rows to get the number of requested rows exactly (if there are enough) and allow for the more convenient syntax:


See Evan's answer for details.

But that's still not exactly random.

How to advance to the next form input when the current input has a value?

you just need to give focus to the next input field (by invoking focus()method on that input element), for example if you're using jQuery this code will simulate the tab key when enter is pressed:

var inputs = $(':input').keypress(function(e){ 
    if (e.which == 13) {
       var nextInput = inputs.get(inputs.index(this) + 1);
       if (nextInput) {

find without recursion

I think you'll get what you want with the -maxdepth 1 option, based on your current command structure. If not, you can try looking at the man page for find.

Relevant entry (for convenience's sake):

-maxdepth levels
          Descend at most levels (a non-negative integer) levels of direc-
          tories below the command line arguments.   `-maxdepth  0'  means
          only  apply the tests and actions to the command line arguments.

Your options basically are:

# Do NOT show hidden files (beginning with ".", i.e., .*):
find DirsRoot/* -maxdepth 0 -type f


#  DO show hidden files:
find DirsRoot/ -maxdepth 1 -type f

How to embed a SWF file in an HTML page?

Use the <embed> element:

<embed src="file.swf" width="854" height="480"></embed>

sys.path different in Jupyter and Python - how to import own modules in Jupyter?

Jupyter has its own PATH variable, JUPYTER_PATH.

Adding this line to the .bashrc file worked for me:

export JUPYTER_PATH=<directory_for_your_module>:$JUPYTER_PATH

Git adding files to repo

git add puts pending files to the so called git 'index' which is local.

After that you use git commit to commit (apply) things in the index.

Then use git push [remotename] [localbranch][:remotebranch] to actually push them to a remote repository.

How to replace a hash key with another key

Previous answers are good enough, but they might update original data. In case if you don't want the original data to be affected, you can try my code.

 newhash=hash.reject{|k| k=='_id'}.merge({id:hash['_id']})

First it will ignore the key '_id' then merge with the updated one.

SessionNotCreatedException: Message: session not created: This version of ChromeDriver only supports Chrome version 81

Do below steps :

  1. Check the version of chrome browser.

  2. download chromedriver of same version from

  3. Give correct path in the pycharm and run the code.

Image steganography that could survive jpeg compression

Quite a few applications seem to implement Steganography on JPEG, so it's feasible:

Here's an article regarding a relevant algorithm (PM1) to get you started:

How do I 'git diff' on a certain directory?

If you want to exclude the sub-directories, you can use

git diff <ref1>..<ref2> -- $(git diff <ref1>..<ref2> --name-only | grep -v /)

Bootstrap Carousel Full Screen

I found an answer on the Try this code:


body {
    height: 100%;

.active {
    height: 100%;

.carousel-inner {
    height: 100%;

/* Background images are set within the HTML using inline CSS, not here */

.fill {
    width: 100%;
    height: 100%;
    background-position: center;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    background-size: cover;
    -o-background-size: cover;

footer {
    margin: 50px 0;


   <div class="carousel-inner">
        <div class="item active">
            <!-- Set the first background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' One');"></div>
            <div class="carousel-caption">
                <h2>Caption 1</h2>
        <div class="item">
            <!-- Set the second background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' Two');"></div>
            <div class="carousel-caption">
                <h2>Caption 2</h2>
        <div class="item">
            <!-- Set the third background image using inline CSS below. -->
            <div class="fill" style="background-image:url(' Three');"></div>
            <div class="carousel-caption">
                <h2>Caption 3</h2>


How to negate code in "if" statement block in JavaScript -JQuery like 'if not then..'

Try negation operator ! before $(this):

if (!$(this).parent().next().is('ul')){

PHP file_get_contents() returns "failed to open stream: HTTP request failed!"

I got a similar problem.

Due to timeout !

Timeout can be indicated like this :

$options = array(
    'http' => array(
        'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
        'method'  => "POST",
        'content' => http_build_query($data2),
        'timeout' => 30,
$context = stream_context_create($options); $retour =
$retour = @file_get_contents("", false, $context);

OpenCV Python rotate image by X degrees around specific point

You can simply use the imutils package to do the rotation. it has two methods

  1. rotate: Rotate the image at specified angle. however the drawback is image might get cropped if it is not a square image.
  2. Rotate_bound: it overcomes the problem happened with rotate. It adjusts the size of the image accordingly while rotating the image.

more info you can get on this blog:

How to run stored procedures in Entity Framework Core?

I used StoredProcedureEFCore nuget package by,EnterpriseLibrary.Data.NetCore,EFCor.SqlServer,EFCore.Tools

I tried DbFirst approach with {Repository pattern}.. i think so


ConfigureServices(IServiceCollection services){
    services.AddDbContext<AppDbContext>(opt => opt
    services.AddScoped<ISomeDAL, SomeDAL>();

    public  class AppDbContext : DbContext{
public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)

ISomeDAl Interface has {GetPropertiesResponse GetAllPropertiesByCity(int CityId);}

public class SomeDAL : ISomeDAL
     private readonly AppDbContext context;

     public SomeDAL(AppDbContext context)
             this.context = context;
     public  GetPropertiesResponse GetAllPropertiesByCity(int CityId)
         //Create Required Objects for response 
         //wont support ref Objects through params
            .AddParam("CityID", CityId).Exec( r =>
                  while (r.Read())

                       ORMapping<GenericRespStatus> orm = new  ORMapping<GenericRespStatus>();
                       orm.AssignObject(r, _Status);

                  if (r.NextResult())

                       while (r.Read())
                           Property = new Property();
                           ORMapping<Property> orm = new ORMapping<Property>();
                           orm.AssignObject(r, Property);
    return new GetPropertiesResponse{Status=_Status,PropertyDetails=_propertyDetailsResult}; 

public class GetPropertiesResponse
     public GenericRespStatus Status;
     public List<Property> PropertyDetails;
     public GetPropertiesResponse()
             PropertyDetails = new List<Property>();
public class GenericRespStatus
     public int ResCode { get; set; }
     public string ResMsg { get; set; }
internal class ORMapping<T>
    public void AssignObject(IDataReader record, T myClass)
        PropertyInfo[] propertyInfos = typeof(T).GetProperties();
        for (int i = 0; i < record.FieldCount; i++)
            if (propertyInfos.Any(obj => obj.Name == record.GetName(i))) //&& record.GetValue(i) != DBNull.Value
                propertyInfos.Single(obj => obj.Name == record.GetName(i)).SetValue(myClass, Convert.ChangeType(record.GetValue(i), record.GetFieldType(i)));

How to write to a file in Scala?

This line helps to write a file from an Array or String.

 new PrintWriter(outputPath) { write(ArrayName.mkString("")); close }

Add some word to all or some rows in Excel?

  • Select All cells that want to change.
  • right click and select Format cell.
  • In category select Custom.
  • In Type select General and insert this formol ----> "k"@

Update a column in MySQL

If you want to update data you should use UPDATE command instead of INSERT

Fix columns in horizontal scrolling


.table-wrapper { 
    margin-left: 120px;
td, th {
    padding: 5px 20px;
    width: 100px;
th:first-child {
    position: fixed;
    left: 5px


$(function () {  _x000D_
  $('.table-wrapper tr').each(function () {_x000D_
    var tr = $(this),_x000D_
        h = 0;_x000D_
    tr.children().each(function () {_x000D_
      var td = $(this),_x000D_
          tdh = td.height();_x000D_
      if (tdh > h) h = tdh;_x000D_
    tr.css({height: h + 'px'});_x000D_
body {_x000D_
    position: relative;_x000D_
.table-wrapper { _x000D_
    margin-left: 120px;_x000D_
td, th {_x000D_
    padding: 5px 20px;_x000D_
    width: 100px;_x000D_
tbody tr {_x000D_
th:first-child {_x000D_
    position: absolute;_x000D_
    left: 5px_x000D_
<!DOCTYPE html>_x000D_
<script src=""></script>_x000D_
  <meta charset="utf-8">_x000D_
  <title>JS Bin</title>_x000D_
    <h1>SOME RANDOM TEXT</h1>_x000D_
<div class="table-wrapper">_x000D_
    <table id="consumption-data" class="data">_x000D_
        <thead class="header">_x000D_
                <th>Item 1</th>_x000D_
                <th>Item 2</th>_x000D_
                <th>Item 3</th>_x000D_
                <th>Item 4</th>_x000D_
        <tbody class="results">_x000D_
                <th>Jan is an awesome month</th>_x000D_
                <td>3163</td>  _x000D_
            <tr>    _x000D_

Open file by its full path in C++

You can use a full path with the fstream classes. The folowing code attempts to open the file demo.txt in the root of the C: drive. Note that as this is an input operation, the file must already exist.

#include <fstream>
#include <iostream>
using namespace std;

int main() {
   ifstream ifs( "c:/demo.txt" );       // note no mode needed
   if ( ! ifs.is_open() ) {                 
      cout <<" Failed to open" << endl;
   else {
      cout <<"Opened OK" << endl;

What does this code produce on your system?

Closing pyplot windows

Please use

A select query selecting a select statement

I was over-complicating myself. After taking a long break and coming back, the desired output could be accomplished by this simple query:

SELECT Sandwiches.[Sandwich Type], Sandwich.Bread, Count(Sandwiches.[SandwichID]) AS [Total Sandwiches]
FROM Sandwiches
GROUP BY Sandwiches.[Sandwiches Type], Sandwiches.Bread;

Thanks for answering, it helped my train of thought.

How do I import an existing Java keystore (.jks) file into a Java installation?

Ok, so here was my process:

keytool -list -v -keystore permanent.jks - got me the alias.

keytool -export -alias alias_name -file certificate_name -keystore permanent.jks - got me the certificate to import.

Then I could import it with the keytool:

keytool -import -alias alias_name -file certificate_name -keystore keystore location

As @Christian Bongiorno says the alias can't already exist in your keystore.

LEFT JOIN only first row

I've used something else (I think better...) and want to share it:

I created a VIEW that has a "group" clause


SELECT * FROM client INNER JOIN vCountries on client_province = province_id

I want to say yet, that I think that we need to do this solution BECAUSE WE DID SOMETHING WRONG IN THE ANALYSIS... at least in my case... but sometimes it's cheaper to do this that to redesign everything...

I hope it helps!

JPA: How to get entity based on field value other than ID?

Refer - Spring docs for query methods

We can add methods in Spring Jpa by passing diff params in methods like:
List<Person> findByEmailAddressAndLastname(EmailAddress emailAddress, String lastname);

// Enabling static ORDER BY for a query 

List<Person> findByLastnameOrderByFirstnameAsc(String lastname);

HTTP URL Address Encoding in Java

How about:

public String UrlEncode(String in_) {

String retVal = "";

try {
    retVal = URLEncoder.encode(in_, "UTF8");
} catch (UnsupportedEncodingException ex) {
    Log.get().exception(Log.Level.Error, "urlEncode ", ex);

return retVal;


Eclipse does not highlight matching variables

I had this issue with Eclipse Mars for PHP developers, 64 bit edition for Windows. I now discovered that highlighting works out-of-the-box with the 32 bit version. Even with a fresh download of the equivalent 64 bit build, highlighting does not work. So I will switch back to 32 bit (this is actually not the first problem I observe with Eclipse 64 bit).


I thought this was the solution, so I installed the 32 bit version in C:\Program Files (x86) and set a shortcut in the "Start" menu. When I started Eclipse from there, highlighting again ceased to work. I now got it working again by deleting the .metadata directory in the workspace (i.e. resetting the workspace settings) and re-importing the projects.

Background service with location listener in android

First you need to create a Service. In that Service, create a class extending LocationListener. For this, use the following code snippet of Service:

public class LocationService extends Service {
public static final String BROADCAST_ACTION = "Hello World";
private static final int TWO_MINUTES = 1000 * 60 * 2;
public LocationManager locationManager;
public MyLocationListener listener;
public Location previousBestLocation = null;

Intent intent;
int counter = 0;

public void onCreate() {
    intent = new Intent(BROADCAST_ACTION);

public void onStart(Intent intent, int startId) {
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    listener = new MyLocationListener();
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
    locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 4000, 0, (LocationListener) listener);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 4000, 0, listener);

public IBinder onBind(Intent intent)
    return null;

protected boolean isBetterLocation(Location location, Location currentBestLocation) {
    if (currentBestLocation == null) {
        // A new location is always better than no location
        return true;

    // Check whether the new location fix is newer or older
    long timeDelta = location.getTime() - currentBestLocation.getTime();
    boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
    boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
    boolean isNewer = timeDelta > 0;

    // If it's been more than two minutes since the current location, use the new location
    // because the user has likely moved
    if (isSignificantlyNewer) {
        return true;
        // If the new location is more than two minutes older, it must be worse
    } else if (isSignificantlyOlder) {
        return false;

    // Check whether the new location fix is more or less accurate
    int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
    boolean isLessAccurate = accuracyDelta > 0;
    boolean isMoreAccurate = accuracyDelta < 0;
    boolean isSignificantlyLessAccurate = accuracyDelta > 200;

    // Check if the old and new location are from the same provider
    boolean isFromSameProvider = isSameProvider(location.getProvider(),

    // Determine location quality using a combination of timeliness and accuracy
    if (isMoreAccurate) {
        return true;
    } else if (isNewer && !isLessAccurate) {
        return true;
    } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
        return true;
    return false;

/** Checks whether two providers are the same */
private boolean isSameProvider(String provider1, String provider2) {
    if (provider1 == null) {
        return provider2 == null;
    return provider1.equals(provider2);

public void onDestroy() {
    // handler.removeCallbacks(sendUpdatesToUI);     
    Log.v("STOP_SERVICE", "DONE");

public static Thread performOnBackgroundThread(final Runnable runnable) {
    final Thread t = new Thread() {
        public void run() {
            try {
            } finally {

    return t;
public class MyLocationListener implements LocationListener

    public void onLocationChanged(final Location loc)
        Log.i("*****", "Location changed");
        if(isBetterLocation(loc, previousBestLocation)) {
            intent.putExtra("Latitude", loc.getLatitude());
            intent.putExtra("Longitude", loc.getLongitude());
            intent.putExtra("Provider", loc.getProvider());


    public void onStatusChanged(String provider, int status, Bundle extras) {


    public void onProviderDisabled(String provider)
        Toast.makeText( getApplicationContext(), "Gps Disabled", Toast.LENGTH_SHORT ).show();

    public void onProviderEnabled(String provider)
        Toast.makeText( getApplicationContext(), "Gps Enabled", Toast.LENGTH_SHORT).show();

Add this Service any where in your project, the way you want! :)

How to subtract/add days from/to a date?

Just subtract a number:

> as.Date("2009-10-01")
[1] "2009-10-01"
> as.Date("2009-10-01")-5
[1] "2009-09-26"

Since the Date class only has days, you can just do basic arithmetic on it.

If you want to use POSIXlt for some reason, then you can use it's slots:

> a <- as.POSIXlt("2009-10-04")
> names(unclass(as.POSIXlt("2009-10-04")))
[1] "sec"   "min"   "hour"  "mday"  "mon"   "year"  "wday"  "yday"  "isdst"
> a$mday <- a$mday - 6
> a
[1] "2009-09-28 EDT"

How can I reference a commit in an issue comment on GitHub?

Answer above is missing an example which might not be obvious (it wasn't to me).

Url could be broken down into parts
                  \_____/\________/       \_______________________________________/
                   |        |                              |
            Account name    |                      Hash of revision
                        Project name              

Hash can be found here (you can click it and will get the url from browser).

enter image description here

Hope this saves you some time.

onChange and onSelect in DropDownList

Simply & Easy : JavaScript code :

function JoinedOrNot(){
    var cat = document.getElementById("mySelect");
    if(cat.value == "yes"){
        document.getElementById("mySelect1").disabled = false;
        document.getElementById("mySelect1").disabled = true;

just add in this line [onChange="JoinedOrNot()"] : <select id="mySelect" onchange="JoinedOrNot()">

it's work fine ;)

How do I view 'git diff' output with my preferred diff tool/ viewer?

For a linux version of how to configure a diff tool on git versions prior to 1.6.3 (1.6.3 added difftool to git) this is a great concise tutorial,

in brief:

Step 1: add this to your .gitconfig

  external = git_diff_wrapper
  diff =

Step 2: create a file named git_diff_wrapper, put it somewhere in your $PATH


vimdiff "$2" "$5"

History or log of commands executed in Git

If you are using CentOS or another Linux flavour then just do Ctrl+R at the prompt and type git.

If you keep hitting Ctrl+R this will do a reverse search through your history for commands that start with git

Filter by Dates in SQL

Well you are trying to compare Date with Nvarchar which is wrong. Should be

Where dates between date1 And date2
-- both date1 & date2 should be date/datetime

If date1,date2 strings; server will convert them to date type before filtering.

Uncaught TypeError: undefined is not a function while using jQuery UI

I don't think jQuery itself includes datetimepicker. You must use jQuery UI instead (src="jquery.ui").

ORA-01861: literal does not match format string

The error means that you tried to enter a literal with a format string, but the length of the format string was not the same length as the literal.

One of these formats is incorrect:

TO_CHAR(t.alarm_datetime, 'YYYY-MM-DD HH24:MI:SS')
TO_DATE(alarm_datetime, 'DD.MM.YYYY HH24:MI:SS')

AssertNull should be used or AssertNotNull

I just want to add that if you want to write special text if It null than you make it like that

  Assert.assertNotNull("The object you enter return null", str1)

Best radio-button implementation for IOS

Try DLRadioButton, works for both Swift and ObjC. You can also use images to indicate selection status or customize your own style.

Check it out at GitHub.

radio button for iOS

**Update: added the option for putting selection indicator on the right side.

**Update: added square button, IBDesignable, improved performance.

**Update: added multiple selection support.

insert multiple rows into DB2 database

None of the above worked for me, the only one working was

insert into tableName  
select 11, 'BALOO' from sysibm.sysdummy1 union all
select 22, nullif('','') AS nullColumn from sysibm.sysdummy1

The nullif is used since it is not possible to pass null in the select statement otherwise.

Transmitting newline character "\n"

Use %0A (URL encoding) instead of \n (C encoding).

How can I make SQL case sensitive string comparison on MySQL?

You can use BINARY to case sensitive like this

select * from tb_app where BINARY android_package='com.Mtime';

unfortunately this sql can't use index, you will suffer a performance hit on queries reliant on that index

mysql> explain select * from tb_app where BINARY android_package='com.Mtime';
| id | select_type | table  | partitions | type | possible_keys | key  | key_len | ref  | rows    | filtered | Extra       |
|  1 | SIMPLE      | tb_app | NULL       | ALL  | NULL          | NULL | NULL    | NULL | 1590351 |   100.00 | Using where |

Fortunately, I have a few tricks to solve this problem

mysql> explain select * from tb_app where android_package='com.Mtime' and BINARY android_package='com.Mtime';
| id | select_type | table  | partitions | type | possible_keys             | key                       | key_len | ref   | rows | filtered | Extra                 |
|  1 | SIMPLE      | tb_app | NULL       | ref  | idx_android_pkg           | idx_android_pkg           | 771     | const |    1 |   100.00 | Using index condition |

Send JSON via POST in C# and Receive the JSON returned?

I found myself using the HttpClient library to query RESTful APIs as the code is very straightforward and fully async'ed.

(Edit: Adding JSON from question for clarity)

  "agent": {                             
    "name": "Agent Name",                
    "version": 1                                                          
  "username": "Username",                                   
  "password": "User Password",
  "token": "xxxxxx"

With two classes representing the JSON-Structure you posted that may look like this:

public class Credentials
    public Agent Agent { get; set; }

    public string Username { get; set; }

    public string Password { get; set; }

    public string Token { get; set; }

public class Agent
    public string Name { get; set; }

    public int Version { get; set; }

you could have a method like this, which would do your POST request:

var payload = new Credentials { 
    Agent = new Agent { 
        Name = "Agent Name",
        Version = 1 
    Username = "Username",
    Password = "User Password",
    Token = "xxxxx"

// Serialize our concrete class into a JSON String
var stringPayload = await Task.Run(() => JsonConvert.SerializeObject(payload));

// Wrap our JSON inside a StringContent which then can be used by the HttpClient class
var httpContent = new StringContent(stringPayload, Encoding.UTF8, "application/json");

using (var httpClient = new HttpClient()) {

    // Do the actual request and await the response
    var httpResponse = await httpClient.PostAsync("http://localhost/api/path", httpContent);

    // If the response contains content we want to read it!
    if (httpResponse.Content != null) {
        var responseContent = await httpResponse.Content.ReadAsStringAsync();

        // From here on you could deserialize the ResponseContent back again to a concrete C# type using Json.Net

How to stop a thread created by implementing runnable interface?

If you use ThreadPoolExecutor, and you use submit() method, it will give you a Future back. You can call cancel() on the returned Future to stop your Runnable task.

makefiles - compile all c files at once

LIBS  = -lkernel32 -luser32 -lgdi32 -lopengl32
CFLAGS = -Wall

# Should be equivalent to your list of C files, if you don't build selectively
SRC=$(wildcard *.c)

test: $(SRC)
    gcc -o $@ $^ $(CFLAGS) $(LIBS)

Move seaborn plot legend to a different position?

it seems you can directly call:

g = sns.factorplot("class", "survived", "sex",
                data=titanic, kind="bar",
                size=6, palette="muted",

g._legend.set_bbox_to_anchor((.7, 1.1))

How can I check if my Element ID has focus?

Write below code in script and also add jQuery library

var getElement = document.getElementById('myID');

if (document.activeElement === getElement) {
        $(document).keydown(function(event) {
            if (event.which === 40) {
                console.log('keydown pressed')

Thank you...

Error handling in C code

Here is an approach which I think is interesting, while requiring some discipline.

This assumes a handle-type variable is the instance on which operate all API functions.

The idea is that the struct behind the handle stores the previous error as a struct with necessary data (code, message...), and the user is provided with a function that returns a pointer to this error object. Each operation will update the pointed object so the user can check its status without even calling functions. As opposed to the errno pattern, the error code is not global, which make the approach thread-safe, as long as each handle is properly used.


MyHandle * h = MyApiCreateHandle();

/* first call checks for pointer nullity, since we cannot retrieve error code
   on a NULL pointer */
if (h == NULL)
     return 0; 

/* from here h is a valid handle */

/* get a pointer to the error struct that will be updated with each call */
MyApiError * err = MyApiGetError(h);

MyApiFileDescriptor * fd = MyApiOpenFile("/path/to/file.ext");

/* we want to know what can go wrong */
if (err->code != MyApi_ERROR_OK) {
    fprintf(stderr, "(%d) %s\n", err->code, err->message);
    return 0;

MyApiRecord record;

/* here the API could refuse to execute the operation if the previous one
   yielded an error, and eventually close the file descriptor itself if
   the error is not recoverable */
MyApiReadFileRecord(h, &record, sizeof(record));

/* we want to know what can go wrong, here using a macro checking for failure */
if (MyApi_FAILED(err)) {
    fprintf(stderr, "(%d) %s\n", err->code, err->message);
    return 0;

BeautifulSoup: extract text from anchor tag


It will print the context of the anchor tags


 statement_title = statement.find('h2',class_='briefing-statement__title')
 statement_title_text = statement_title.a.contents[0]

Python Graph Library

I second zweiterlinde's suggestion to use python-graph. I've used it as the basis of a graph-based research project that I'm working on. The library is well written, stable, and has a good interface. The authors are also quick to respond to inquiries and reports.

File upload from <input type="file">

Another way using template reference variable and ViewChild, as proposed by Frelseren:

import { ViewChild } from '@angular/core';

  selector: 'my-app',
  template: `
      <input type="file" #fileInput/>
export class AppComponent {
  @ViewChild("fileInput") fileInputVariable: any;
  randomMethod() {
    const files = this.fileInputVariable.nativeElement.files;

Also see

Angular - "has no exported member 'Observable'"

The angular-split component is not supported in Angular 6, so to make it compatible with Angular 6 install following dependency in your application

To get this working until it's updated use:

"dependencies": {
"angular-split": "1.0.0-rc.3",
"rxjs": "^6.2.2",
    "rxjs-compat": "^6.2.2",

'react-scripts' is not recognized as an internal or external command

Running the npm update command solved my problem.

Printing Even and Odd using two Threads in Java

Simplest Solution!!

public class OddEvenWithThread {
    public static void main(String a[]) {
        Thread t1 = new Thread(new OddEvenRunnable(0), "Even Thread");
        Thread t2 = new Thread(new OddEvenRunnable(1), "Odd Thread");


class OddEvenRunnable implements Runnable {
    Integer evenflag;
    static Integer number = 1;
    static Object lock = new Object();

    OddEvenRunnable(Integer evenFlag) {
        this.evenflag = evenFlag;

    public void run() {
        while (number < 10) {
            synchronized (lock) {
                try {
                    while (number % 2 != evenflag) {
                } catch (InterruptedException e) {

                System.out.println(Thread.currentThread().getName() + " " + number);

Laravel - Session store not set on request

Do you can use ->stateless() before the ->redirect(). Then you dont need the session anymore.

'Field required a bean of type that could not be found.' error spring restful API using mongodb

I also had the same error:



Field repository in required a bean of type '' that could not be found.


Consider defining a bean of type '' in your here

And my packages were constructed in the same way as mentioned in the accepted answer. I fixed my issue by adding EnableMongoRepositories annotation in the main class like this:

@EnableMongoRepositories(basePackageClasses = CustomerRepository.class)
public class CampaignAPI {

    public static void main(String[] args) {, args);

If you need to add multiple don't forget the curly braces:

    = {
        MSASMSRepository.class, APartyMappingRepository.class

Keep only date part when using pandas.to_datetime

Pandas DatetimeIndex and Series have a method called normalize that does exactly what you want.

You can read more about it in this answer.

It can be used as ser.dt.normalize()

How to use 'git pull' from the command line?

One more option is to add the path of the privatekey file like this in terminal:

ssh-add "path to the privatekeyfile"

and then execute the pull command

Java Singleton and Synchronization

Yes, it is necessary. There are several methods you can use to achieve thread safety with lazy initialization:

Draconian synchronization:

private static YourObject instance;

public static synchronized YourObject getInstance() {
    if (instance == null) {
        instance = new YourObject();
    return instance;

This solution requires that every thread be synchronized when in reality only the first few need to be.

Double check synchronization:

private static final Object lock = new Object();
private static volatile YourObject instance;

public static YourObject getInstance() {
    YourObject r = instance;
    if (r == null) {
        synchronized (lock) {    // While we were waiting for the lock, another 
            r = instance;        // thread may have instantiated the object.
            if (r == null) {  
                r = new YourObject();
                instance = r;
    return r;

This solution ensures that only the first few threads that try to acquire your singleton have to go through the process of acquiring the lock.

Initialization on Demand:

private static class InstanceHolder {
    private static final YourObject instance = new YourObject();

public static YourObject getInstance() {
    return InstanceHolder.instance;

This solution takes advantage of the Java memory model's guarantees about class initialization to ensure thread safety. Each class can only be loaded once, and it will only be loaded when it is needed. That means that the first time getInstance is called, InstanceHolder will be loaded and instance will be created, and since this is controlled by ClassLoaders, no additional synchronization is necessary.

Adding an onclick event to a table row

Here is how I do this. I create a table with a thead and tbody tags. And then add a click event to the tbody element by id.

    document.getElementById("mytbody").click = clickfunc;
    function clickfunc(e) {
        // to find what td element has the data you are looking for
        var tdele =[x].innerHTML;
        // to find the row
        var trele =;
            <th>Header 1</th>
            <th>Header 2</th>
    <tbody id="mytbody">
        <tr><td>Data Row</td><td>1</td></tr>
        <tr><td>Data Row</td><td>2</td></tr>
        <tr><td>Data Row</td><td>3</td></tr>

Spring schemaLocation fails when there is no internet connection

If there is no internet connection in your platform and you use Eclipse, follow these steps (it solves my problem)

  1. Find the exact xsd files (You can unzip these files from their jars. For example, spring-beans-x.y.xsd in spring-beans-x.y.z.RELEASE.jar)
  2. Add these xsd files to Eclipse XML Catalog. (Preferences->XML->XML Catalog, Add files)
  3. Add these files location to configuration file. (Be careful, write the exact version of file)


xsi:schemaLocation=" "

Unlink of file Failed. Should I try again?

I encountered this issue while doing a git pull.

I tried git gc and it resolved my problem.

How do I validate a date in rails?

Using the chronic gem:

class MyModel < ActiveRecord::Base
  validate :valid_date?

  def valid_date?
    unless Chronic.parse(from_date)
      errors.add(:from_date, "is missing or invalid")


mysql said: Cannot connect: invalid settings. xampp

Opsss. after I change user to 'admin', it doesn't have privelege to add database.. so I change back the user to 'root'.

Then I change the password from the browser.

  1. Go to http://localhost/security/ and then click on the link http://localhost/security/xamppsecurity.php . After that change pasword for superuser to 'root'.

  2. After that open your http://localhost/phpmyadmin/

    Now it works.

NULL value for int in Update statement

Assuming the column is set to support NULL as a value:

   SET column = NULL

Be aware of the database NULL handling - by default in SQL Server, NULL is an INT. So if the column is a different data type you need to CAST/CONVERT NULL to the proper data type:


...assuming column is a DATETIME data type in the example above.

Git - How to use .netrc file on Windows to save user and password

This will let Git authenticate on HTTPS using .netrc:

  • The file should be named _netrc and located in c:\Users\<username>.
  • You will need to set an environment variable called HOME=%USERPROFILE% (set system-wide environment variables using the System option in the control panel. Depending on the version of Windows, you may need to select "Advanced Options".).
  • The password stored in the _netrc file cannot contain spaces (quoting the password will not work).

How do I get the path of the current executed file in Python?

Simply add the following:

from sys import *
path_to_current_file = sys.argv[0]


from sys import *

How to save a PNG image server-side, from a base64 data string

I had to replace spaces with plus symbols str_replace(' ', '+', $img); to get this working.

Here is the full code

$img = $_POST['img']; // Your data 'data:image/png;base64,AAAFBfj42Pj4';
$img = str_replace('data:image/png;base64,', '', $img);
$img = str_replace(' ', '+', $img);
$data = base64_decode($img);
file_put_contents('/tmp/image.png', $data);

Hope that helps.

How do I push a local Git branch to master branch in the remote?

As an extend to @Eugene's answer another version which will work to push code from local repo to master/develop branch .

Switch to branch ‘master’:

$ git checkout master

Merge from local repo to master:

$ git merge --no-ff FEATURE/<branch_Name>

Push to master:

$ git push

How to make a simple rounded button in Storyboard?

I am using Xcode Version 11.4

In the attribute inspector, you can define the corner radius.

It won't show in the Storyboard but it will work fine when you run the project.

enter image description here

Checking character length in ruby

Instead of using a regular expression, just check if string.length > 25

How can I close a Twitter Bootstrap popover with a click from anywhere (else) on the page?

Presuming that only one popover can be visible at any time, you can use a set of flags to mark when there's a popover visible, and only then hide them.

If you set the event listener on the document body, it will trigger when you click the element marked with 'popup-marker'. So you'll have to call stopPropagation() on the event object. And apply the same trick when clicking on the popover itself.

Below is a working JavaScript code that does this. It uses jQuery >= 1.7

jQuery(function() {
    var isVisible = false;

    var hideAllPopovers = function() {
       $('.popup-marker').each(function() {

        html: true,
        trigger: 'manual'
    }).on('click', function(e) {
        // if any other popovers are visible, hide them
        if(isVisible) {


        // handle clicking on the popover itself
        $('.popover').off('click').on('click', function(e) {
            e.stopPropagation(); // prevent event for bubbling up => will not get caught with document.onclick

        isVisible = true;

    $(document).on('click', function(e) {
        isVisible = false;

The only caveat is that you won't be able to open 2 popovers at the same time. But I think that would be confusing for the user, anyway :-)

How do I scroll a row of a table into view (element.scrollintoView) using jQuery?

much simpler:

$("selector for element").get(0).scrollIntoView();

if more than one item returns in the selector, the get(0) will get only the first item.

In Java, what is the best way to determine the size of an object?

Back when I worked at Twitter, I wrote a utility for calculating deep object size. It takes into account different memory models (32-bit, compressed oops, 64-bit), padding, subclass padding, works correctly on circular data structures and arrays. You can just compile this one .java file; it has no external dependencies:

Install opencv for Python 3.3

I had a lot of trouble getting opencv 3.0 to work on OSX with python3 bindings and virtual environments. The other answers helped a lot, but it still took a bit. Hopefully this will help the next person. Save this to Then download opencv, modify the variables in the below shell script, cross your fingers, and run it (. ./ For debugging, use the other posts, especially James Fletchers.

Don't forget to add the opencv lib dir to your PYTHONPATH.

Note - this also downloads opencv-contrib, where many of the functions have been moved. And they are also now referenced by a different namespace than the documentation - for instance SIFT is now under cv2.xfeatures2d.SIFT_create. Uggh.

# Install opencv with python3 bindings:

# First download opencv and put in OPENCV_DIR

# Edit this section
CONTRIB_TAG="3.0.0"  # This will also download opencv_contrib and checkout the appropriate tag

# Run it

set -e  # Exit if error


if  [[ ! -d opencv_contrib ]]
    echo '**Get contrib modules'
    [[ -d opencv_contrib ]] || mkdir opencv_contrib
    git clone [email protected]:Itseez/opencv_contrib.git .
    git checkout ${CONTRIB_TAG}
    echo '**Contrib directory already exists. Not fetching.'


echo '**Going to do: cmake'
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D PYTHON_EXECUTABLE=${PYTHON_DIR}/bin/python3 \
    -D PYTHON_LIBRARY=${PYTHON_DIR}/lib/libpython3.4m.dylib \
    -D PYTHON_INCLUDE_DIR=${PYTHON_DIR}/include/python3.4m \
    -D PYTHON_NUMPY_INCLUDE_DIRS=${PYTHON_DIR}/lib/python3.4/site-packages/numpy/core/include/numpy \
    -D PYTHON_PACKAGES_PATH=${PYTHON_DIR}lib/python3.4/site-packages \
    -D OPENCV_EXTRA_MODULES_PATH=opencv_contrib/modules \
    -D BUILD_opencv_legacy=OFF  \

echo '**Going to do: make'
make -j${NUM_THREADS}

echo '**Going to do: make install'
sudo make  install

echo '**Add the following to your .bashrc: export PYTHONPATH=${PYTHONPATH}:${OPENCV_DIR}/lib'

echo '**Testing if it worked'
python3 -c 'import cv2'
echo 'opencv properly installed with python3 bindings!'  # The script will exit if the above failed.

React.createElement: type is invalid -- expected a string

This is an error that is some how had to debug. As it has been said many times, improper import/export can cause this error but surprisingly i got this error from a small bug in my react-router-dom authentication setup below is my case:


const PrivateRoute = ({ component: Component, }) => (
        render={(props) => (token ? <Component {...props} /> : <Redirect to={{ pathname: "/login" }} />)}


const PrivateRoute = ({ component: Component, token, }) => (
        render={(props) => (token ? <Component {...props} /> : <Redirect to={{ pathname: "/login" }} />)}

The only difference was I was deconstructing the token in the PrivateRoute component. By the way the token is gotten from localstorage like this const token = localStorage.getItem("authUser"); so if it is not there I know the user is not authenticated. This can also cause that error.

2D cross-platform game engine for Android and iOS?

I've tried AppGameKit, It's both c++ and Basic. It's very easy to code 2d games in the Basic varient, with physics, collision and heaps more. It's also in active development, and really cheap (65$). The main problem is that it's really hard to compile for Android (you need to download heaps of files and follow difficult guides and things like that) My opinion is that it isn't yet good enough for commercial use, but is good for indie programmers It's got a medium size community

How to get my Android device Internal Download Folder path

if a device has an SD card, you use:


if you don't have an SD card, you use:


if there is no SD card, you can create your own directory on the device locally.

    //if there is no SD card, create new directory objects to make directory on device
        if (Environment.getExternalStorageState() == null) {
                        //create new file directory object
            directory = new File(Environment.getDataDirectory()
                    + "/RobotiumTestLog/");
            photoDirectory = new File(Environment.getDataDirectory()
                    + "/Robotium-Screenshots/");
             * this checks to see if there are any previous test photo files
             * if there are any photos, they are deleted for the sake of
             * memory
            if (photoDirectory.exists()) {
                File[] dirFiles = photoDirectory.listFiles();
                if (dirFiles.length != 0) {
                    for (int ii = 0; ii <= dirFiles.length; ii++) {
            // if no directory exists, create new directory
            if (!directory.exists()) {

            // if phone DOES have sd card
        } else if (Environment.getExternalStorageState() != null) {
            // search for directory on SD card
            directory = new File(Environment.getExternalStorageDirectory()
                    + "/RobotiumTestLog/");
            photoDirectory = new File(
                            + "/Robotium-Screenshots/");
            if (photoDirectory.exists()) {
                File[] dirFiles = photoDirectory.listFiles();
                if (dirFiles.length > 0) {
                    for (int ii = 0; ii < dirFiles.length; ii++) {
                    dirFiles = null;
            // if no directory exists, create new directory to store test
            // results
            if (!directory.exists()) {
        }// end of SD card checking

add permissions on your manifest.xml

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Happy coding..

Getting request payload from POST request in Java servlet

With Apache Commons IO you can do this in one line.


The opposite of Intersect()

As stated, if you want to get 4 as the result, you can do like this:

var nonintersect = array2.Except(array1);

If you want the real non-intersection (also both 1 and 4), then this should do the trick:

var nonintersect = array1.Except(array2).Union( array2.Except(array1));

This will not be the most performant solution, but for small lists it should work just fine.

What happens to a declared, uninitialized variable in C? Does it have a value?

Because computers have finite storage capacity, automatic variables will typically be held in storage elements (whether registers or RAM) that have previously been used for some other arbitrary purpose. If a such a variable is used before a value has been assigned to it, that storage may hold whatever it held previously, and so the contents of the variable will be unpredictable.

As an additional wrinkle, many compilers may keep variables in registers which are larger than the associated types. Although a compiler would be required to ensure that any value which is written to a variable and read back will be truncated and/or sign-extended to its proper size, many compilers will perform such truncation when variables are written and expect that it will have been performed before the variable is read. On such compilers, something like:

uint16_t hey(uint32_t x, uint32_t mode)
{ uint16_t q; 
  if (mode==1) q=2; 
  if (mode==3) q=4; 
  return q; }

 uint32_t wow(uint32_t mode) {
   return hey(1234567, mode);

might very well result in wow() storing the values 1234567 into registers 0 and 1, respectively, and calling foo(). Since x isn't needed within "foo", and since functions are supposed to put their return value into register 0, the compiler may allocate register 0 to q. If mode is 1 or 3, register 0 will be loaded with 2 or 4, respectively, but if it is some other value, the function may return whatever was in register 0 (i.e. the value 1234567) even though that value is not within the range of uint16_t.

To avoid requiring compilers to do extra work to ensure that uninitialized variables never seem to hold values outside their domain, and avoid needing to specify indeterminate behaviors in excessive detail, the Standard says that use of uninitialized automatic variables is Undefined Behavior. In some cases, the consequences of this may be even more surprising than a value being outside the range of its type. For example, given:

void moo(int mode)
  if (mode < 5)
  hey(0, mode);      

a compiler could infer that because invoking moo() with a mode which is greater than 3 will inevitably lead to the program invoking Undefined Behavior, the compiler may omit any code which would only be relevant if mode is 4 or greater, such as the code which would normally prevent the launch of nukes in such cases. Note that neither the Standard, nor modern compiler philosophy, would care about the fact that the return value from "hey" is ignored--the act of trying to return it gives a compiler unlimited license to generate arbitrary code.

printf() formatting for hex

The # part gives you a 0x in the output string. The 0 and the x count against your "8" characters listed in the 08 part. You need to ask for 10 characters if you want it to be the same.

int i = 7;

printf("%#010x\n", i);  // gives 0x00000007
printf("0x%08x\n", i);  // gives 0x00000007
printf("%#08x\n", i);   // gives 0x000007

Also changing the case of x, affects the casing of the outputted characters.

printf("%04x", 4779); // gives 12ab
printf("%04X", 4779); // gives 12AB

What is the $? (dollar question mark) variable in shell scripting?

It is the returned error code of the last executed command. 0 = success

How to add Apache HTTP API (legacy) as compile-time dependency to build.grade for Android M?

Just copied file: org.apache.http.legacy.jar from Android/Sdk/platforms/android-23/optional folder into project folder app/libs.

Worked like charm for 23.1.1.

How to force HTTPS using a web.config file

To augment LazyOne's answer, here is an annotated version of the answer.

     <clear />
     <rule name="Redirect all requests to https" stopProcessing="true">
       <match url="(.*)" />
         <conditions logicalGrouping="MatchAll">
           <add input="{HTTPS}" pattern="off" ignoreCase="true" />
            type="Redirect" url="https://{HTTP_HOST}{REQUEST_URI}" 
            redirectType="Permanent" appendQueryString="false" />

Clear all the other rules that might already been defined on this server. Create a new rule, that we will name "Redirect all requests to https". After processing this rule, do not process any more rules! Match all incoming URLs. Then check whether all of these other conditions are true: HTTPS is turned OFF. Well, that's only one condition (but make sure it's true). If it is, send a 301 Permanent redirect back to the client at Don't add the query string at the end of that, because it would duplicate the query string!

This is what the properties, attributes, and some of the values mean.

  • clear removes all server rules that we might otherwise inherit.
  • rule defines a rule.
    • name an arbitrary (though unique) name for the rule.
    • stopProcessing whether to forward the request immediately to the IIS request pipeline or first to process additional rules.
  • match when to run this rule.
    • url a pattern against which to evaluate the URL
  • conditions additional conditions about when to run this rule; conditions are processed only if there is first a match.
    • logicalGrouping whether all the conditions must be true (MatchAll) or any of the conditions must be true (MatchAny); similar to AND vs OR.
  • add adds a condition that must be met.
    • input the input that a condition is evaluating; input can be server variables.
    • pattern the standard against which to evaluate the input.
    • ignoreCase whether capitalization matters or not.
  • action what to do if the match and its conditions are all true.
    • type can generally be redirect (client-side) or rewrite (server-side).
    • url what to produce as a result of this rule; in this case, concatenate https:// with two server variables.
    • redirectType what HTTP redirect to use; this one is a 301 Permanent.
    • appendQueryString whether to add the query string at the end of the resultant url or not; in this case, we are setting it to false, because the {REQUEST_URI} already includes it.

The server variables are

  • {HTTPS} which is either OFF or ON.
  • {HTTP_HOST} is, and
  • {REQUEST_URI} includes the rest of the URI, e.g. /home?key=value
    • the browser handles the #fragment (see comment from LazyOne).

See also:

make an ID in a mysql table auto_increment (after the fact)




But none of these will work if your bar_id is a foreign key in another table: you'll be getting

an error 1068: Multiple primary key defined

To solve this, temporary disable foreign key constraint checks by

set foreign_key_checks = 0;

and after running the statements above, enable them back again.

set foreign_key_checks = 1;

Detect if an input has text in it using CSS -- on a page I am visiting and do not control?

You can take advantage of the placeholder and use:

input:not(:placeholder-shown) {
  border: 1px solid red;

PHP : send mail in localhost

It is configured to use localhost:25 for the mail server.

The error message says that it can't connect to localhost:25.

Therefore you have two options:

  1. Install / Properly configure an SMTP server on localhost port 25
  2. Change the configuration to point to some other SMTP server that you can connect to

scrollTop animation without jquery


<button onclick="scrollToTop(1000);"></button>

1# JavaScript (linear):

function scrollToTop (duration) {
    // cancel if already on top
    if (document.scrollingElement.scrollTop === 0) return;

    const totalScrollDistance = document.scrollingElement.scrollTop;
    let scrollY = totalScrollDistance, oldTimestamp = null;

    function step (newTimestamp) {
        if (oldTimestamp !== null) {
            // if duration is 0 scrollY will be -Infinity
            scrollY -= totalScrollDistance * (newTimestamp - oldTimestamp) / duration;
            if (scrollY <= 0) return document.scrollingElement.scrollTop = 0;
            document.scrollingElement.scrollTop = scrollY;
        oldTimestamp = newTimestamp;

2# JavaScript (ease in and out):

function scrollToTop (duration) {
    // cancel if already on top
    if (document.scrollingElement.scrollTop === 0) return;

    const cosParameter = document.scrollingElement.scrollTop / 2;
    let scrollCount = 0, oldTimestamp = null;

    function step (newTimestamp) {
        if (oldTimestamp !== null) {
            // if duration is 0 scrollCount will be Infinity
            scrollCount += Math.PI * (newTimestamp - oldTimestamp) / duration;
            if (scrollCount >= Math.PI) return document.scrollingElement.scrollTop = 0;
            document.scrollingElement.scrollTop = cosParameter + cosParameter * Math.cos(scrollCount);
        oldTimestamp = newTimestamp;
  - pi is the length/end point of the cosinus intervall (see below)
  - newTimestamp indicates the current time when callbacks queued by requestAnimationFrame begin to fire.
    (for more information see
  - newTimestamp - oldTimestamp equals the delta time

    a * cos (bx + c) + d                        | c translates along the x axis = 0
  = a * cos (bx) + d                            | d translates along the y axis = 1 -> only positive y values
  = a * cos (bx) + 1                            | a stretches along the y axis = cosParameter = window.scrollY / 2
  = cosParameter + cosParameter * (cos bx)  | b stretches along the x axis = scrollCount = Math.PI / (scrollDuration / (newTimestamp - oldTimestamp))
  = cosParameter + cosParameter * (cos scrollCount * x)


  • Duration in milliseconds (1000ms = 1s)
  • Second script uses the cos function. Example curve:

enter image description here

3# Simple scrolling library on Github

Core dump file is not generated

If one is on a Linux distro (e.g. CentOS, Debian) then perhaps the most accessible way to find out about core files and related conditions is in the man page. Just run the following command from a terminal:

man 5 core

Environment variable substitution in sed

Dealing with VARIABLES within sed

[root@gislab00207 ldom]# echo domainname: None > /tmp/1.txt

[root@gislab00207 ldom]# cat /tmp/1.txt

domainname: None

[root@gislab00207 ldom]# echo ${DOMAIN_NAME}

[root@gislab00207 ldom]# cat /tmp/1.txt | sed -e 's/domainname: None/domainname: ${DOMAIN_NAME}/g'

 --- Below is the result -- very funny.

domainname: ${DOMAIN_NAME}

 --- You need to single quote your variable like this ... 

[root@gislab00207 ldom]# cat /tmp/1.txt | sed -e 's/domainname: None/domainname: '${DOMAIN_NAME}'/g'

--- The right result is below 


Get an object's class name at runtime

If you already know what types to expect (for example, when a method returns a union type), then you can use type guards.

For example, for primitive types you can use a typeof guard:

if (typeof thing === "number") {
  // Do stuff

For complex types you can use an instanceof guard:

if (thing instanceof Array) {
  // Do stuff

Do not want scientific notation on plot axis

Normally setting axis limit @ max of your variable is enough

a <- c(0:1000000)
b <- c(0:1000000)

plot(a, b, ylim = c(0, max(b)))

How to replace master branch in Git, entirely, from another branch?

What about using git branch -m to rename the master branch to another one, then rename seotweaks branch to master? Something like this:

git branch -m master old-master
git branch -m seotweaks master
git push -f origin master

This might remove commits in origin master, please check your origin master before running git push -f origin master.

R: `which` statement with multiple conditions

The && function is not vectorized. You need the & function:

EUR <- PCs[which(PCs$V13 < 9 & PCs$V13 > 3), ]

Python unittest - opposite of assertRaises?

you can try like that. try: self.assertRaises(None,function,arg1, arg2) except: pass if you don't put code inside try block it will through exception' AssertionError: None not raised " and test case will be failed. Test case will be pass if put inside try block which is expected behaviour.

adding css class to multiple elements

Try using:

.button input, .button a {
    // css stuff

Also, read up on CSS.

Edit: If it were me, I'd add the button class to the element, not to the parent tag. Like so:


<a href="#" class='button'>BUTTON TEXT</a>
<input type="submit" class='button' value='buttontext' />


.button {
    // css stuff

For specific css stuff use:

input.button {
    // css stuff
a.button {
    // css stuff

text-overflow: ellipsis not working

Add the Following lines in CSS for ellipsis to work

 p {
     display: block; // change it as per your requirement
     overflow: hidden;
     text-overflow: ellipsis;
     white-space: nowrap;

htaccess "order" Deny, Allow, Deny

Just use order allow,deny instead and remove the deny from all line.

How to escape special characters in building a JSON string?

regarding AlexB's post:

 \'  Apostrophe or single quote
 \"  Double quote

escaping single quotes is only valid in single quoted json strings
escaping double quotes is only valid in double quoted json strings


'Bart\'s car'       -> valid
'Bart says \"Hi\"'  -> invalid

Heroku + node.js error (Web process failed to bind to $PORT within 60 seconds of launch)

I realized that I don't need the port number in the request endpoint, so the endpoint was and not

The listen() call can be without host and callback:


Calculate the date yesterday in JavaScript

solve boundary date problem (2020, 01, 01) -> 2019, 12, 31

var now = new Date();
return new Date(now.getMonth() - 1 === 0 ? now.getFullYear() - 1 : now.getFullYear(),
                now.getDate() - 1 === 0 ? now.getMonth() - 1: now.getMonth(),
                now.getDate() - 1);

Permission denied (publickey,gssapi-keyex,gssapi-with-mic)

I had the same problem and for some reason The sshKeys was not syncing up with my user on the instance.

I created another user by adding --ssh_user=anotheruser to gcutil command.

The gcutil looked like this

gcutil --service_version="v1" --project="project"  --ssh_user=anotheruser ssh  --zone="us-central1-a" "inst1"

How can I convert string date to NSDate?

For Swift 3

func stringToDate(_ str: String)->Date{
    let formatter = DateFormatter()
    formatter.dateFormat="yyyy-MM-dd hh:mm:ss Z"
    return str)!
func dateToString(_ str: Date)->String{
    var dateFormatter = DateFormatter()
    return dateFormatter.string(from: str)

Scikit-learn train_test_split with indices

Here's the simplest solution (Jibwa made it seem complicated in another answer), without having to generate indices yourself - just using the ShuffleSplit object to generate 1 split.

import numpy as np 
from sklearn.model_selection import ShuffleSplit # or StratifiedShuffleSplit
sss = ShuffleSplit(n_splits=1, test_size=0.1)

data_size = 100
X = np.reshape(np.random.rand(data_size*2),(data_size,2))
y = np.random.randint(2, size=data_size)

sss.get_n_splits(X, y)
train_index, test_index = next(sss.split(X, y)) 

X_train, X_test = X[train_index], X[test_index] 
y_train, y_test = y[train_index], y[test_index]

Adding space/padding to a UILabel

Easy padding:

import UIKit

    class NewLabel: UILabel {

        override func textRectForBounds(bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {

            return CGRectInset(self.bounds, CGFloat(15.0), CGFloat(15.0))

        override func drawRect(rect: CGRect) {

            super.drawTextInRect(CGRectInset(self.bounds,CGFloat(5.0), CGFloat(5.0)))


Semi-transparent color layer over background-image?

You need then a wrapping element with the bg image and in it the content element with the bg color:

<div id="Wrapper">
  <div id="Content">
    <!-- content here -->

and the css:



How do I raise the same Exception with a custom message in Python?

Python 3 built-in exceptions have the strerror field:

except ValueError as err:
  err.strerror = "New error message"
  raise err

How can I determine the type of an HTML element in JavaScript?

nodeName is the attribute you are looking for. For example:

var elt = document.getElementById('foo');

Note that nodeName returns the element name capitalized and without the angle brackets, which means that if you want to check if an element is an <div> element you could do it as follows:

elt.nodeName == "DIV"

While this would not give you the expected results:

elt.nodeName == "<div>"

Why is Visual Studio 2010 not able to find/open PDB files?

Referring to the first thread / another possibility VS cant open or find pdb file of the process is when you have your executable running in the background. I was working with mpiexec and ran into this issue. Always check your task manager and kill any exec process that your gonna build in your project. Once I did that, it debugged or built fine.

Also, if you try to continue with the warning , the breakpoints would not be hit and it would not have the current executable

psql: could not connect to server: No such file or directory (Mac OS X)

SUPER NEWBIE ALERT: I'm just learning web development and the particular tutorial I was following mentioned I have to install Postgres but didn't actually mention I have to run it as well... Once I opened the Postgres application everything was fine and dandy.

Best way to encode Degree Celsius symbol into web page?

  1. The degree sign belongs to the number, and not to the "C". You can regard the degree sign as a number symbol, just like the minus sign.
  2. There shall not be any space between the digits and the degree sign.
  3. There shall be a non-breaking space between the degree sign and the "C".

How can I select all elements without a given class in jQuery?

You could use this to pick all li elements without class:

$('ul#list li:not([class])')

Timeout for python requests.get entire response

timeout = int(seconds)

Since requests >= 2.4.0, you can use the timeout argument, i.e:

requests.get('', timeout=10)


timeout is not a time limit on the entire response download; rather, an exception is raised if the server has not issued a response for timeout seconds ( more precisely, if no bytes have been received on the underlying socket for timeout seconds). If no timeout is specified explicitly, requests do not time out.

Call an overridden method from super class in typescript

below is an generic example

    //base class
    class A {
        // The virtual method
        protected virtualStuff1?():void;
        public Stuff2(){
            //Calling overridden child method by parent if implemented
            this.virtualStuff1 && this.virtualStuff1();
            alert("Baseclass Stuff2");
    //class B implementing virtual method
    class B extends A{
        // overriding virtual method
        public virtualStuff1()
            alert("Class B virtualStuff1");
    //Class C not implementing virtual method
    class C extends A{
    var b1 = new B();
    var c1= new C();

How do I negate a condition in PowerShell?

You almost had it with Not. It should be:

if (-Not (Test-Path C:\Code)) {
    write "it doesn't exist!"

You can also use !: if (!(Test-Path C:\Code)){}

Just for fun, you could also use bitwise exclusive or, though it's not the most readable/understandable method.

if ((test-path C:\code) -bxor 1) {write "it doesn't exist!"}

When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used?

Does this answer your question?

I have never used reinterpret_cast, and wonder whether running into a case that needs it isn't a smell of bad design. In the code base I work on dynamic_cast is used a lot. The difference with static_cast is that a dynamic_cast does runtime checking which may (safer) or may not (more overhead) be what you want (see msdn).

How can I select random files from a directory in bash?

How about a Perl solution slightly doctored from Mr. Kang over here:
How can I shuffle the lines of a text file on the Unix command line or in a shell script?

$ ls | perl -MList::Util=shuffle -e '@lines = shuffle(<>); print @lines[0..4]'

python list in sql query as parameter

string.join the list values separated by commas, and use the format operator to form a query string.

myquery = "select name from studens where id in (%s)" % ",".join(map(str,mylist))

(Thanks, blair-conrad)

How can I solve equations in Python?

Use a different tool. Something like Wolfram Alpha, Maple, R, Octave, Matlab or any other algebra software package.

As a beginner you should probably not attempt to solve such a non-trivial problem.

How to display a JSON representation and not [Object Object] on the screen

<li *ngFor="let obj of myArray">{{obj | json}}</li>

How to import a module in Python with importlib.import_module

And don't forget to create a with each folder/subfolder (even if they are empty)

How can I show data using a modal when clicking a table row (using bootstrap)?

One thing you can do is get rid of all those onclick attributes and do it the right way with bootstrap. You don't need to open them manually; you can specify the trigger and even subscribe to events before the modal opens so that you can do your operations and populate data in it.

I am just going to show as a static example which you can accommodate in your real world.

On each of your <tr>'s add a data attribute for id (i.e. data-id) with the corresponding id value and specify a data-target, which is a selector you specify, so that when clicked, bootstrap will select that element as modal dialog and show it. And then you need to add another attribute data-toggle=modal to make this a trigger for modal.

  <tr data-toggle="modal" data-id="1" data-target="#orderModal">
  <tr data-toggle="modal" data-id="2" data-target="#orderModal">
  <tr data-toggle="modal" data-id="3" data-target="#orderModal">

And now in the javascript just set up the modal just once and event listen to its events so you can do your work.

        keyboard: true,
        backdrop: "static",

    }).on('show', function(){ //subscribe to show method
          var getIdFromRow = $('tr').data('id'); //get the id from tr
        //make your ajax call populate items or what even you need
        $(this).find('#orderDetails').html($('<b> Order Id selected: ' + getIdFromRow  + '</b>'))


Do not use inline click attributes any more. Use event bindings instead with vanilla js or using jquery.

Alternative ways here:

Demo2 or Demo3

How to efficiently calculate a running standard deviation?

As the following answer describes: Does pandas/scipy/numpy provide a cumulative standard deviation function? The Python Pandas module contains a method to calculate the running or cumulative standard deviation. For that you'll have to convert your data into a pandas dataframe (or a series if it is 1D), but there are functions for that.

A simple jQuery form validation script

You can simply use the jQuery Validate plugin as follows.


$(document).ready(function () {

    $('#myform').validate({ // initialize the plugin
        rules: {
            field1: {
                required: true,
                email: true
            field2: {
                required: true,
                minlength: 5



<form id="myform">
    <input type="text" name="field1" />
    <input type="text" name="field2" />
    <input type="submit" />




Standard Rules:

Optional Rules available with the additional-methods.js file:

email2 (optional TLD)
url2 (optional TLD)

How to start a Process as administrator mode in C#

This works when I try it. I double-checked with two sample programs:

using System;
using System.Diagnostics;

namespace ConsoleApplication1 {
  class Program {
    static void Main(string[] args) {

using System;
using System.IO;

namespace ConsoleApplication2 {
  class Program {
    static void Main(string[] args) {
      try {
        File.WriteAllText(@"c:\program files\test.txt", "hello world");
      catch (Exception ex) {

First verified that I get the UAC bomb:

System.UnauthorizedAccessException: Access to the path 'c:\program files\test.txt' is denied.
// etc..

Then added a manifest to ConsoleApplication1 with the phrase:

    <requestedExecutionLevel level="requireAdministrator" uiAccess="false" />

No bomb. And a file I can't easily delete :) This is consistent with several previous tests on various machines running Vista and Win7. The started program inherits the security token from the starter program. If the starter has acquired admin privileges, the started program has them as well.

Remote debugging Tomcat with Eclipse

In the tomcat bin directory wherecatalina.bat or .sh is found (aka {CATALINA_BASE}/bin), edit (create if not there):


Add the following line:

CATALINA_OPTS="-Xdebug -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n"

That's all you need to do, you don't need to edit the catalina.bat (or .sh) file.

See the comments in catalina.bator

You may have to adjust the syntax for your particular environment/situation. For example, if you already have CATALINA_OPTS defined, you might do something like this (in a windows environment):

set CATALINA_OPTS=%CATALINA_OPTS% -Xdebug -Xrunjdwp:transport=dt_socket,address=8088,server=y,suspend=n

To debug from Eclipse:

run->Debug configurations...->Remote Java Application->New

and specify a name, the project you are debugging, and the tomcat host and debug port specified above.

Does the Java &= operator apply & or &&?

i came across a similar situation using booleans where I wanted to avoid calling b() if a was already false.

This worked for me:

a &= a && b()

IF EXISTS before INSERT, UPDATE, DELETE for optimization





patterns work as expected under high concurrency. Both may fail. Both may fail very frequently. MERGE is the king - it holds up much better.Let us do some stress testing and see for ourselves.

Here is the table we shall be using:

      i1 INT NOT NULL ,
      i2 INT NOT NULL ,
      version ROWVERSION
    ) ;

        ( ID, i1, i2 )
VALUES  ( 1, 0, 0 ) ;    

IF EXISTS(…) THEN pattern frequently fails under high concurrency.

Let us insert or update rows in a loop using the following simple logic: if a row with given ID exists, update it, and otherwise insert a new one. The following loop implements this logic. Cut and paste it into two tabs, switch into text mode in both tabs, and run them simultaneously.

-- hit Ctrl+T to execute in text mode



SET @ID = 0 ;
WHILE @ID > -100000
    BEGIN ;
        SET @ID = ( SELECT  MIN(ID)
                    FROM    dbo.TwoINTs
                  ) - 1 ;
        BEGIN TRY ;

            IF EXISTS ( SELECT  *
                        FROM    dbo.TwoINTs
                        WHERE   ID = @ID )
                BEGIN ;
                    UPDATE  dbo.TwoINTs
                    SET     i1 = 1
                    WHERE   ID = @ID ;
                END ;
                BEGIN ;
                    INSERT  INTO dbo.TwoINTs
                            ( ID, i1, i2 )
                    VALUES  ( @ID, 0, 0 ) ;
                END ;
            COMMIT ; 
        END TRY
        BEGIN CATCH ;
            ROLLBACK ; 
            SELECT  error_message() ;
        END CATCH ;
    END ; 

When we run this script simultaneously in two tabs, we shall immediately get a huge amount of primary key violations in both tabs. This demonstrates how unreliable the IF EXISTS pattern is when it executes under high concurrency.

Note: this example also demonstrates that it is not safe to use SELECT MAX(ID)+1 or SELECT MIN(ID)-1 as the next available unique value if we do it under concurrency.

How to launch an application from a browser?

Some applications launches themselves by protocols. like itunes with "itms://" links. I don't know however how you can register that with windows.

Python list of dictionaries search

This is a general way of searching a value in a list of dictionaries:

def search_dictionaries(key, value, list_of_dictionaries):
    return [element for element in list_of_dictionaries if element[key] == value]

javascript onclick increment number

I know this is an old post but its relevant to what I'm working on currently.

What I'm aiming to do is create next/previous page buttons at the top of a html page, and say I'm on 'book.html', with the current 'display' ID content being 'page-1.html' through ajax, if i click the 'next' button it will load 'page-2.html' through ajax, WITHOUT reloading the page.

How would I go about doing this through AJAX as I have seen many examples but most of them are completely different, and most examples of using AJAX are for WordPress forms and stuff.

Currently using the below line will open the entire page, I want to know the best way to go about using AJAX instead if possible :) window.location(url);

I'm incorportating the below code as an example:

var i = 1;
var url = "pages/page-" + i + ".html";

    function incPage() {
    if (i < 10) {
        window.location = url; 
        //load next page in body using AJAX request

    } else if (i = 10) {
        i = 0;
    document.getElementById("display").innerHTML = i;

function decPage() {
    if (i > 0) {
        window.location = url; 
        //load previous page in body using AJAX request
    } else if (i = 0) {
        i = 10;
    document.getElementById("display").innerHTML = i;

Scanner only reads first word instead of line

Use input.nextLine(); instead of;

How do I set a ViewModel on a window in XAML using DataContext property?

You might want to try Catel. It allows you to define a DataWindow class (instead of Window), and that class automatically creates the view model for you. This way, you can use the declaration of the ViewModel as you did in your original post, and the view model will still be created and set as DataContext.

See this article for an example.

How to calculate md5 hash of a file using javascript

The following snippet shows an example, which can archive a throughput of 400 MB/s while reading and hashing the file.

It is using a library called hash-wasm, which is based on WebAssembly and calculates the hash faster than js-only libraries. As of 2020, all modern browsers support WebAssembly.

const chunkSize = 64 * 1024 * 1024;
const fileReader = new FileReader();
let hasher = null;

function hashChunk(chunk) {
  return new Promise((resolve, reject) => {
    fileReader.onload = async(e) => {
      const view = new Uint8Array(;


const readFile = async(file) => {
  if (hasher) {
  } else {
    hasher = await hashwasm.createMD5();

  const chunkNumber = Math.floor(file.size / chunkSize);

  for (let i = 0; i <= chunkNumber; i++) {
    const chunk = file.slice(
      chunkSize * i,
      Math.min(chunkSize * (i + 1), file.size)
    await hashChunk(chunk);

  const hash = hasher.digest();
  return Promise.resolve(hash);

const fileSelector = document.getElementById("file-input");
const resultElement = document.getElementById("result");

fileSelector.addEventListener("change", async(event) => {
  const file =[0];

  resultElement.innerHTML = "Loading...";
  const start =;
  const hash = await readFile(file);
  const end =;
  const duration = end - start;
  const fileSizeMB = file.size / 1024 / 1024;
  const throughput = fileSizeMB / (duration / 1000);
  resultElement.innerHTML = `
    Hash: ${hash}<br>
    Duration: ${duration} ms<br>
    Throughput: ${throughput.toFixed(2)} MB/s
<script src=""></script>
<!-- defines the global `hashwasm` variable -->

<input type="file" id="file-input">
<div id="result"></div>

Why do we check up to the square root of a prime number to determine if it is prime?

Yes, as it was properly explained above, it's enough to iterate up to Math.floor of a number's square root to check its primality (because sqrt covers all possible cases of division; and Math.floor, because any integer above sqrt will already be beyond its range).

Here is a runnable JavaScript code snippet that represents a simple implementation of this approach – and its "runtime-friendliness" is good enough for handling pretty big numbers (I tried checking both prime and not prime numbers up to 10**12, i.e. 1 trillion, compared results with the online database of prime numbers and encountered no errors or lags even on my cheap phone):

function isPrime(num) {
  if (num % 2 === 0 || num < 3 || !Number.isInteger(num)) {
    return num === 2;
  } else {
    const sqrt = Math.floor(Math.sqrt(num));
    for (let i = 3; i <= sqrt; i += 2) {
      if (num % i === 0) {
        return false;
    return true;
<label for="inp">Enter a number and click "Check!":</label><br>
<input type="number" id="inp"></input>
<button onclick="alert(isPrime(+document.getElementById('inp').value) ? 'Prime' : 'Not prime')" type="button">Check!</button>

python pandas: Remove duplicates by columns A, keeping the row with the highest value in column B

This takes the last. Not the maximum though:

In [10]: df.drop_duplicates(subset='A', keep="last")
   A   B
1  1  20
3  2  40
4  3  10

You can do also something like:

In [12]: df.groupby('A', group_keys=False).apply(lambda x: x.loc[x.B.idxmax()])
   A   B
1  1  20
2  2  40
3  3  10

Execution time of C program

ANSI C only specifies second precision time functions. However, if you are running in a POSIX environment you can use the gettimeofday() function that provides microseconds resolution of time passed since the UNIX Epoch.

As a side note, I wouldn't recommend using clock() since it is badly implemented on many(if not all?) systems and not accurate, besides the fact that it only refers to how long your program has spent on the CPU and not the total lifetime of the program, which according to your question is what I assume you would like to measure.

Convert form data to JavaScript object with jQuery

For a quick, modern solution, use the JSONify jQuery plugin. The example below is taken verbatim from the GitHub README. All credit to Kushal Pandya, author of the plugin.


<form id="myform">
    <input type="text" name="name"/>
    <input type="text" name="email"/>
    <input type="password" name="password"/>




{"name":"Joe User","email":"[email protected]","password":"mypass"}

If you want to do a jQuery POST with this JSON object:

$('#mybutton').click(function() {
    $.post('/api/user', JSON.stringify($('#myform').jsonify()));

Don't change link color when a link is clicked

You need to use an explicit color value (e.g. #000 or blue) for the color-property. none is invalid here. The initial value is browser-specific and cannot be restored using CSS. Keep in mind that there are some other pseudo-classes than :active, too.

Servlet Mapping using web.xml

It allows servlets to have multiple servlet mappings:


It allows filters to be mapped on the particular servlet:


Your proposal would support neither of them. Note that the web.xml is read and parsed only once during application's startup, not on every HTTP request as you seem to think.

Since Servlet 3.0, there's the @WebServlet annotation which minimizes this boilerplate:

public class Servlet1 extends HttpServlet {

See also:

How do I use two submit buttons, and differentiate between which one was used to submit the form?

If you can't put value on buttons. I have just a rough solution. Put a hidden field. And when one of the buttons are clicked before submitting, populate the value of hidden field with like say 1 when first button clicked and 2 if second one is clicked. and in submit page check for the value of this hidden field to determine which one is clicked.

Node.js/Express.js App Only Works on Port 3000

Answer according to current version of express

If you talk about the current version of express, if you run app.listen() to start listening without specifying port, Express will chose a random port for your application, to find out about which port it is currently running on use

app.listen(0, () => {

should output the port of your app. Moreover that first parameter 0 can be totally ignored but is not recommended

LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup

In my case, it's because I accidentally removed (not deleted) the stdafx.h and targetver.h files in the Header Files section.

Add these files back to Header Files and the problem is solved.

I had these:

#pragma comment( linker, "/entry:\"mainCRTStartup\"" ) // set the entry point to be main()

I just need to comment that (by prepending //) and it's good.

How to communicate between Docker containers via "hostname"

As far as I know, by using only Docker this is not possible. You need some DNS to map container ip:s to hostnames.

If you want out of the box solution. One solution is to use for example Kontena. It comes with network overlay technology from Weave and this technology is used to create virtual private LAN networks for each service and every service can be reached by service_name.kontena.local-address.

Here is simple example of Wordpress application's YAML file where Wordpress service connects to MySQL server with wordpress-mysql.kontena.local address:

  image: wordpress:4.1                                                             
  stateful: true                                                                   
    - 80:80                                                                      
    - mysql:wordpress-mysql                                                        
    - WORDPRESS_DB_HOST=wordpress-mysql.kontena.local                              
    - WORDPRESS_DB_PASSWORD=secret                                                 
  image: mariadb:5.5                                                               
  stateful: true                                                                   

C# Telnet Library

I ended up finding MinimalistTelnet and adapted it to my uses. I ended up needing to be able to heavily modify the code due to the unique** device that I am attempting to attach to.

** Unique in this instance can be validly interpreted as brain-dead.

Creating object with dynamic keys

You can't define an object literal with a dynamic key. Do this :

var o = {};
o[key] = value;
return o;

There's no shortcut (edit: there's one now, with ES6, see the other answer).

how to list all sub directories in a directory

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TRIAL
    public class Class1
        static void Main(string[] args)
           string[] fileArray = Directory.GetDirectories("YOUR PATH");
           for (int i = 0; i < fileArray.Length; i++)


Display the binary representation of a number in C?

Use a lookup table, like:

char *table[16] = {"0000", "0001", .... "1111"};

then print each nibble like this

printf("%s%s", table[a / 0x10], table[a % 0x10]);

Surely you can use just one table, but it will be marginally faster and too big.

How is __eq__ handled in Python and in what order?

When Python2.x sees a == b, it tries the following.

  • If type(b) is a new-style class, and type(b) is a subclass of type(a), and type(b) has overridden __eq__, then the result is b.__eq__(a).
  • If type(a) has overridden __eq__ (that is, type(a).__eq__ isn't object.__eq__), then the result is a.__eq__(b).
  • If type(b) has overridden __eq__, then the result is b.__eq__(a).
  • If none of the above are the case, Python repeats the process looking for __cmp__. If it exists, the objects are equal iff it returns zero.
  • As a final fallback, Python calls object.__eq__(a, b), which is True iff a and b are the same object.

If any of the special methods return NotImplemented, Python acts as though the method didn't exist.

Note that last step carefully: if neither a nor b overloads ==, then a == b is the same as a is b.


Hibernate Error: org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session

I had a similar problem. In my case I had forgotten to set the increment_by value in the database to be the same like the one used by the cache_size and allocationSize. (The arrows point to the mentioned attributes)


CREATED         26.07.16
LAST_DDL_TIME   26.07.16
MIN_VALUE       1
MAX_VALUE       9999999999999999999999999999
CACHE_SIZE      20 <-


@SequenceGenerator(name = "mySG", schema = "my", 
sequenceName = "my_id_seq", allocationSize = 20 <-)

HTML5 image icon to input placeholder

I don't know whether there's a better answer out there as time goes by but this is simple and it works;

input[type='email'] {
  background: white url(images/mail.svg) no-repeat ;
input[type='email']:focus {
  background-image: none;

Style it up to suit.

Bower: ENOGIT Git is not installed or not in the PATH

I had the same problem and needed to restart the cmd - and the problem goes away.

How can I obtain the element-wise logical NOT of a pandas Series?

In support to the excellent answers here, and for future convenience, there may be a case where you want to flip the truth values in the columns and have other values remain the same (nan values for instance)

In[1]: series = pd.Series([True, np.nan, False, np.nan])
In[2]: series = series[series.notna()] #remove nan values
In[3]: series # without nan                                            
0     True
2    False
dtype: object

# Out[4] expected to be inverse of Out[3], pandas applies bitwise complement 
# operator instead as in `lambda x : (-1*x)-1`

In[4]: ~series
0    -2
2    -1
dtype: object

as a simple non-vectorized solution you can just, 1. check types2. inverse bools

In[1]: series = pd.Series([True, np.nan, False, np.nan])

In[2]: series = series.apply(lambda x : not x if x is bool else x)
0     True
1      NaN
2    False
3      NaN
dtype: object

Call two functions from same onclick

You can create a single function that calls both of those, and then use it in the event.

function myFunction(){

And then, for the button:

<input id="btn" type="button" value="click" onclick="myFunction();"/>

How to track down access violation "at address 00000000"

I will second madExcept and similar tools, like Eurekalog, but I think you can come a good way with FastMM also. With full debugmode enabled, it should give you some clues of whats wrong.

Anyway, even though Delphi uses FastMM as default, it's worth getting the full FastMM for it's additional control over logging.

How Do I Insert a Byte[] Into an SQL Server VARBINARY Column

You can do something like this, very simple and efficient solution: What i did was actually use a parameter instead of basic placeholder, created a SqlParameter object and used another existing execution method. For e.g in your scenario:

string sql = "INSERT INTO mssqltable (varbinarycolumn) VALUES (@img)";
SqlParameter param = new SqlParameter("img", arraytoinsert); //where img is your parameter name in the query
ExecuteStoreCommand(sql, param);

This should work like a charm, provided you have an open sql connection established.

How do I run a Python program in the Command Prompt in Windows 7?

Just want to mention, when you do:

cd C:\Python27
python Tools\Scripts\

The PATH variable in "user variables for administrator" is changed.

But you can also follow the others' answer to open:

System -> advanced system settings -> advanced -> Environment Variables,

and modify/add the variable Path in "System Variables", add ;C:\Python27 at the end of it.

JWT authentication for ASP.NET Web API

I answered this question: How to secure an ASP.NET Web API 4 years ago using HMAC.

Now, lots of things changed in security, especially that JWT is getting popular. In this answer, I will try to explain how to use JWT in the simplest and basic way that I can, so we won't get lost from jungle of OWIN, Oauth2, ASP.NET Identity... :)

If you don't know about JWT tokens, you need to take a look at:

Basically, a JWT token looks like this:

<base64-encoded header>.<base64-encoded claims>.<base64-encoded signature>



A JWT token has three sections:

  1. Header: JSON format which is encoded in Base64
  2. Claims: JSON format which is encoded in Base64.
  3. Signature: Created and signed based on Header and Claims which is encoded in Base64.

If you use the website with the token above, you can decode the token and see it like below:

A screenshot of with the raw jwt source and the decoded JSON it represents

Technically, JWT uses a signature which is signed from headers and claims with security algorithm specified in the headers (example: HMACSHA256). Therefore, JWT must be transferred over HTTPs if you store any sensitive information in its claims.

Now, in order to use JWT authentication, you don't really need an OWIN middleware if you have a legacy Web Api system. The simple concept is how to provide JWT token and how to validate the token when the request comes. That's it.

In the demo I've created (github), to keep the JWT token lightweight, I only store username and expiration time. But this way, you have to re-build new local identity (principal) to add more information like roles, if you want to do role authorization, etc. But, if you want to add more information into JWT, it's up to you: it's very flexible.

Instead of using OWIN middleware, you can simply provide a JWT token endpoint by using a controller action:

public class TokenController : ApiController
    // This is naive endpoint for demo, it should use Basic authentication
    // to provide token or POST request
    public string Get(string username, string password)
        if (CheckUser(username, password))
            return JwtManager.GenerateToken(username);

        throw new HttpResponseException(HttpStatusCode.Unauthorized);

    public bool CheckUser(string username, string password)
        // should check in the database
        return true;

This is a naive action; in production you should use a POST request or a Basic Authentication endpoint to provide the JWT token.

How to generate the token based on username?

You can use the NuGet package called System.IdentityModel.Tokens.Jwt from Microsoft to generate the token, or even another package if you like. In the demo, I use HMACSHA256 with SymmetricKey:

/// <summary>
/// Use the below code to generate symmetric Secret Key
///     var hmac = new HMACSHA256();
///     var key = Convert.ToBase64String(hmac.Key);
/// </summary>
private const string Secret = "db3OIsj+BXE9NZDy0t8W3TcNekrF+2d/1sFnWG4HnV8TZY30iTOdtVWJG8abWvB1GlOgJuQZdcF2Luqm/hccMw==";

public static string GenerateToken(string username, int expireMinutes = 20)
    var symmetricKey = Convert.FromBase64String(Secret);
    var tokenHandler = new JwtSecurityTokenHandler();

    var now = DateTime.UtcNow;
    var tokenDescriptor = new SecurityTokenDescriptor
        Subject = new ClaimsIdentity(new[]
            new Claim(ClaimTypes.Name, username)

        Expires = now.AddMinutes(Convert.ToInt32(expireMinutes)),
        SigningCredentials = new SigningCredentials(
            new SymmetricSecurityKey(symmetricKey), 

    var stoken = tokenHandler.CreateToken(tokenDescriptor);
    var token = tokenHandler.WriteToken(stoken);

    return token;

The endpoint to provide the JWT token is done.

How to validate the JWT when the request comes?

In the demo, I have built JwtAuthenticationAttribute which inherits from IAuthenticationFilter (more detail about authentication filter in here).

With this attribute, you can authenticate any action: you just have to put this attribute on that action.

public class ValueController : ApiController
    public string Get()
        return "value";

You can also use OWIN middleware or DelegateHander if you want to validate all incoming requests for your WebAPI (not specific to Controller or action)

Below is the core method from authentication filter:

private static bool ValidateToken(string token, out string username)
    username = null;

    var simplePrinciple = JwtManager.GetPrincipal(token);
    var identity = simplePrinciple.Identity as ClaimsIdentity;

    if (identity == null)
        return false;

    if (!identity.IsAuthenticated)
        return false;

    var usernameClaim = identity.FindFirst(ClaimTypes.Name);
    username = usernameClaim?.Value;

    if (string.IsNullOrEmpty(username))
       return false;

    // More validate to check whether username exists in system

    return true;

protected Task<IPrincipal> AuthenticateJwtToken(string token)
    string username;

    if (ValidateToken(token, out username))
        // based on username to get more information from database 
        // in order to build local identity
        var claims = new List<Claim>
            new Claim(ClaimTypes.Name, username)
            // Add more claims if needed: Roles, ...

        var identity = new ClaimsIdentity(claims, "Jwt");
        IPrincipal user = new ClaimsPrincipal(identity);

        return Task.FromResult(user);

    return Task.FromResult<IPrincipal>(null);

The workflow is to use the JWT library (NuGet package above) to validate the JWT token and then return back ClaimsPrincipal. You can perform more validation, like check whether user exists on your system, and add other custom validations if you want.

The code to validate JWT token and get principal back:

public static ClaimsPrincipal GetPrincipal(string token)
        var tokenHandler = new JwtSecurityTokenHandler();
        var jwtToken = tokenHandler.ReadToken(token) as JwtSecurityToken;

        if (jwtToken == null)
            return null;

        var symmetricKey = Convert.FromBase64String(Secret);

        var validationParameters = new TokenValidationParameters()
            RequireExpirationTime = true,
            ValidateIssuer = false,
            ValidateAudience = false,
            IssuerSigningKey = new SymmetricSecurityKey(symmetricKey)

        SecurityToken securityToken;
        var principal = tokenHandler.ValidateToken(token, validationParameters, out securityToken);

        return principal;
    catch (Exception)
        //should write log
        return null;

If the JWT token is validated and the principal is returned, you should build a new local identity and put more information into it to check role authorization.

Remember to add config.Filters.Add(new AuthorizeAttribute()); (default authorization) at global scope in order to prevent any anonymous request to your resources.

You can use Postman to test the demo:

Request token (naive as I mentioned above, just for demo):

GET http://localhost:{port}/api/token?username=cuong&password=1

Put JWT token in the header for authorized request, example:

GET http://localhost:{port}/api/value

Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1bmlxdWVfbmFtZSI6ImN1b25nIiwibmJmIjoxNDc3NTY1MjU4LCJleHAiOjE0Nzc1NjY0NTgsImlhdCI6MTQ3NzU2NTI1OH0.dSwwufd4-gztkLpttZsZ1255oEzpWCJkayR_4yvNL1s

The demo can be found here:

setting the id attribute of an input element dynamically in IE: alternative for setAttribute method

Forget setAttribute(): it's badly broken and doesn't always do what you might expect in old IE (IE <= 8 and compatibility modes in later versions). Use the element's properties instead. This is generally a good idea, not just for this particular case. Replace your code with the following, which will work in all major browsers:

var hiddenInput = document.createElement("input"); = "uniqueIdentifier";
hiddenInput.type = "hidden";                     
hiddenInput.value = ID;
hiddenInput.className = "ListItem";


The nasty hack in the second code block in the question is unnecessary, and the code above works fine in all major browsers, including IE 6. See The reason why you get null in your alert() is that when it is called, the new input is not yet in the document, hence the document.getElementById() call cannot find it.

How to search text using php if ($text contains "World")

What you need is strstr()(or stristr(), like LucaB pointed out). Use it like this:

if(strstr($text, "world")) {/* do stuff */}

Convert integer into its character equivalent, where 0 => a, 1 => b, etc

Javascript's String.fromCharCode(code1, code2, ..., codeN) takes an infinite number of arguments and returns a string of letters whose corresponding ASCII values are code1, code2, ... codeN. Since 97 is 'a' in ASCII, we can adjust for your indexing by adding 97 to your index.

function indexToChar(i) {
  return String.fromCharCode(i+97); //97 in ASCII is 'a', so i=0 returns 'a', 
                                    // i=1 returns 'b', etc

Validate SSL certificates with Python

You can use Twisted to verify certificates. The main API is CertificateOptions, which can be provided as the contextFactory argument to various functions such as listenSSL and startTLS.

Unfortunately, neither Python nor Twisted comes with a the pile of CA certificates required to actually do HTTPS validation, nor the HTTPS validation logic. Due to a limitation in PyOpenSSL, you can't do it completely correctly just yet, but thanks to the fact that almost all certificates include a subject commonName, you can get close enough.

Here is a naive sample implementation of a verifying Twisted HTTPS client which ignores wildcards and subjectAltName extensions, and uses the certificate-authority certificates present in the 'ca-certificates' package in most Ubuntu distributions. Try it with your favorite valid and invalid certificate sites :).

import os
import glob
from OpenSSL.crypto import load_certificate, FILETYPE_PEM
from twisted.python.urlpath import URLPath
from twisted.internet.ssl import ContextFactory
from twisted.internet import reactor
from twisted.web.client import getPage
certificateAuthorityMap = {}
for certFileName in glob.glob("/etc/ssl/certs/*.pem"):
    # There might be some dead symlinks in there, so let's make sure it's real.
    if os.path.exists(certFileName):
        data = open(certFileName).read()
        x509 = load_certificate(FILETYPE_PEM, data)
        digest = x509.digest('sha1')
        # Now, de-duplicate in case the same cert has multiple names.
        certificateAuthorityMap[digest] = x509
class HTTPSVerifyingContextFactory(ContextFactory):
    def __init__(self, hostname):
        self.hostname = hostname
    isClient = True
    def getContext(self):
        ctx = Context(TLSv1_METHOD)
        store = ctx.get_cert_store()
        for value in certificateAuthorityMap.values():
        ctx.set_verify(VERIFY_PEER | VERIFY_FAIL_IF_NO_PEER_CERT, self.verifyHostname)
        return ctx
    def verifyHostname(self, connection, x509, errno, depth, preverifyOK):
        if preverifyOK:
            if self.hostname != x509.get_subject().commonName:
                return False
        return preverifyOK
def secureGet(url):
    return getPage(url, HTTPSVerifyingContextFactory(URLPath.fromString(url).netloc))
def done(result):
    print 'Done!', len(result)

Encode html entities in javascript

If you're already using jQuery, try html().

// "&lt;script&gt;alert("gotcha!")&lt;/script&gt;"

An in-memory text node is instantiated, and html() is called on it.

It's ugly, it wastes a bit of memory, and I have no idea if it's as thorough as something like the he library but if you're already using jQuery, maybe this is an option for you.

Taken from blog post Encode HTML entities with jQuery by Felix Geisendörfer.

How to uncommit my last commit in Git

Be careful, reset --hard will remove your local (uncommitted) modifications, too.

git reset --hard HEAD^

note: if you're on windows you'll need to quote the HEAD^ so

git reset --hard "HEAD^"

If you want to revert the commit WITHOUT throwing away work, use the --soft flag instead of --hard

How to Delete node_modules - Deep Nested Folder in Windows

simple just run for windows I haven't tested it for other operating systems

rm -r node_modules

in fact, you can delete any folder with this.

like rm -r AnyFolderWhichIsNotDeletableFromShiftDeleteOrDelete.

just open the gitbash move to root of the folder and run this command

Hope this will help.

Thanks, Ajay Kotnala

Why can't I reference my class library?

If using TFS, performing a Get latest (recursive) doesn't always work. Instead, I force a get latest by clicking Source control => Get specific version then clicking both boxes. This tends to work.

enter image description here

If it still doesn't work then deleting the suo file (usually found in the same place as the solution) forces visual studio to get all the files from the source (and subsequently rebuild the suo file).

If that doesn't work then try closing all your open files and closing Visual studio. When you next open Visual studio it should be fixed. There is a resharper bug that is resolved this way.

how to show lines in common (reverse diff)?

Found this answer on a question listed as a duplicate. I find grep to be more admin-friendly than comm, so if you just want the set of matching lines (useful for comparing CSVs, for instance) simply use

grep -F -x -f file1 file2

or the simplified fgrep version

fgrep -xf file1 file2

Plus, you can use file2* to glob and look for lines in common with multiple files, rather than just two.

Some other handy variations include

  • -n flag to show the line number of each matched line
  • -c to only count the number of lines that match
  • -v to display only the lines in file2 that differ (or use diff).

Using comm is faster, but that speed comes at the expense of having to sort your files first. It isn't very useful as a 'reverse diff'.

MySql ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

You must run your mysql by xampp-controle.exe in folder XAMPP. After that login:

mysql -u root

View a file in a different Git branch without changing branches

Add the following to your ~/.gitconfig file

  cat = "!git show \"$1:$2\" #"

And then try this


Personally I prefer separate parameters without a colon. Why? This choice mirrors the parameters of the checkout command, which I tend to use rather frequently and I find it thus much easier to remember than the bizarro colon-separated parameter of the show command.

How to deal with missing src/test/java source folder in Android/Maven project?

Removing the m2 plugin from startup-up plugin's list and doing a Maven->Update Projects on all the projects worked for me.

Note** One should not create additional folders to avoid merging them while using SVN/Git based branches.