Programs & Examples On #Organization

This tag pertains to the organization of source files and other assets in directory structures, organization of actual source code itself, logical organization of application data, and (occasionally) to organizing development projects.

Best practice for Django project working directory structure

There're two kind of Django "projects" that I have in my ~/projects/ directory, both have a bit different structure.:

  • Stand-alone websites
  • Pluggable applications

Stand-alone website

Mostly private projects, but doesn't have to be. It usually looks like this:

~/projects/project_name/

docs/               # documentation
scripts/
  manage.py         # installed to PATH via setup.py
project_name/       # project dir (the one which django-admin.py creates)
  apps/             # project-specific applications
    accounts/       # most frequent app, with custom user model
    __init__.py
    ...
  settings/         # settings for different environments, see below
    __init__.py
    production.py
    development.py
    ...
        
  __init__.py       # contains project version
  urls.py
  wsgi.py
static/             # site-specific static files
templates/          # site-specific templates
tests/              # site-specific tests (mostly in-browser ones)
tmp/                # excluded from git
setup.py
requirements.txt
requirements_dev.txt
pytest.ini
...

Settings

The main settings are production ones. Other files (eg. staging.py, development.py) simply import everything from production.py and override only necessary variables.

For each environment, there are separate settings files, eg. production, development. I some projects I have also testing (for test runner), staging (as a check before final deploy) and heroku (for deploying to heroku) settings.

Requirements

I rather specify requirements in setup.py directly. Only those required for development/test environment I have in requirements_dev.txt.

Some services (eg. heroku) requires to have requirements.txt in root directory.

setup.py

Useful when deploying project using setuptools. It adds manage.py to PATH, so I can run manage.py directly (anywhere).

Project-specific apps

I used to put these apps into project_name/apps/ directory and import them using relative imports.

Templates/static/locale/tests files

I put these templates and static files into global templates/static directory, not inside each app. These files are usually edited by people, who doesn't care about project code structure or python at all. If you are full-stack developer working alone or in a small team, you can create per-app templates/static directory. It's really just a matter of taste.

The same applies for locale, although sometimes it's convenient to create separate locale directory.

Tests are usually better to place inside each app, but usually there is many integration/functional tests which tests more apps working together, so global tests directory does make sense.

Tmp directory

There is temporary directory in project root, excluded from VCS. It's used to store media/static files and sqlite database during development. Everything in tmp could be deleted anytime without any problems.

Virtualenv

I prefer virtualenvwrapper and place all venvs into ~/.venvs directory, but you could place it inside tmp/ to keep it together.

Project template

I've created project template for this setup, django-start-template

Deployment

Deployment of this project is following:

source $VENV/bin/activate
export DJANGO_SETTINGS_MODULE=project_name.settings.production
git pull
pip install -r requirements.txt

# Update database, static files, locales
manage.py syncdb  --noinput
manage.py migrate
manage.py collectstatic --noinput
manage.py makemessages -a
manage.py compilemessages

# restart wsgi
touch project_name/wsgi.py

You can use rsync instead of git, but still you need to run batch of commands to update your environment.

Recently, I made django-deploy app, which allows me to run single management command to update environment, but I've used it for one project only and I'm still experimenting with it.

Sketches and drafts

Draft of templates I place inside global templates/ directory. I guess one can create folder sketches/ in project root, but haven't used it yet.

Pluggable application

These apps are usually prepared to publish as open-source. I've taken example below from django-forme

~/projects/django-app/

docs/
app/
tests/
example_project/
LICENCE
MANIFEST.in
README.md
setup.py
pytest.ini
tox.ini
.travis.yml
...

Name of directories is clear (I hope). I put test files outside app directory, but it really doesn't matter. It is important to provide README and setup.py, so package is easily installed through pip.

What is the best project structure for a Python application?

The "Python Packaging Authority" has a sampleproject:

https://github.com/pypa/sampleproject

It is a sample project that exists as an aid to the Python Packaging User Guide's Tutorial on Packaging and Distributing Projects.

Throwing exceptions from constructors

Although I have not worked C++ at a professional level, in my opinion, it is OK to throw exceptions from the constructors. I do that(if needed) in .Net. Check out this and this link. It might be of your interest.

grep using a character vector with multiple patterns

Have you tried the match() or charmatch() functions?

Example use:

match(c("A1", "A9", "A6"), myfile$Letter)

Why doesn't Java allow overriding of static methods?

Static methods are treated as global by the JVM, there are not bound to an object instance at all.

It could conceptually be possible if you could call static methods from class objects (like in languages like Smalltalk) but it's not the case in Java.

EDIT

You can overload static method, that's ok. But you can not override a static method, because class are no first-class object. You can use reflection to get the class of an object at run-time, but the object that you get does not parallel the class hierarchy.

class MyClass { ... }
class MySubClass extends MyClass { ... }

MyClass obj1 = new MyClass();
MySubClass obj2 = new MySubClass();

ob2 instanceof MyClass --> true

Class clazz1 = obj1.getClass();
Class clazz2 = obj2.getClass();

clazz2 instanceof clazz1 --> false

You can reflect over the classes, but it stops there. You don't invoke a static method by using clazz1.staticMethod(), but using MyClass.staticMethod(). A static method is not bound to an object and there is hence no notion of this nor super in a static method. A static method is a global function; as a consequence there is also no notion of polymorphism and, therefore, method overriding makes no sense.

But this could be possible if MyClass was an object at run-time on which you invoke a method, as in Smalltalk (or maybe JRuby as one comment suggest, but I know nothing of JRuby).

Oh yeah... one more thing. You can invoke a static method through an object obj1.staticMethod() but that really syntactic sugar for MyClass.staticMethod() and should be avoided. It usually raises a warning in modern IDE. I don't know why they ever allowed this shortcut.

Dynamically create Bootstrap alerts box through JavaScript

FWIW I created a JavaScript class that can be used at run-time.
It's over on GitHub, here.

There is a readme there with a more in-depth explanation, but I'll do a quick example below:

var ba = new BootstrapAlert();
ba.addP("Some content here");
$("body").append(ba.render());

The above would create a simple primary alert with a paragraph element inside containing the text "Some content here".

There are also options that can be set on initialisation.
For your requirement you'd do:

var ba = new BootstrapAlert({
    dismissible: true,
    background: 'warning'
});
ba.addP("Invalid Credentials");
$("body").append(ba.render());

The render method will return an HTML element, which can then be inserted into the DOM. In this case, we append it to the bottom of the body tag.

This is a work in progress library, but it still is in a very good working order.

Load local javascript file in chrome for testing?

The easiest way I found was to copy your file contents into you browser console and hit enter. The disadvantage of this approach is that you can only debug with console.log statements.

invalid_grant trying to get oAuth token from google

I had the same error message 'invalid_grant' and it was because the authResult['code'] send from client side javascript was not received correctly on the server.

Try to output it back from the server to see if it is correct and not an empty string.

What is the difference between @Inject and @Autowired in Spring Framework? Which one to use under what condition?

Better use @Inject all the time. Because it is java configuration approach(provided by sun) which makes our application agnostic to the framework. So if you spring also your classes will work.

If you use @Autowired it will works only with spring because @Autowired is spring provided annotation.

Reset AutoIncrement in SQL Server after Delete

DBCC CHECKIDENT('databasename.dbo.tablename', RESEED, number)

if number=0 then in the next insert the auto increment field will contain value 1

if number=101 then in the next insert the auto increment field will contain value 102


Some additional info... May be useful to you

Before giving auto increment number in above query, you have to make sure your existing table's auto increment column contain values less that number.

To get the maximum value of a column(column_name) from a table(table1), you can use following query

 SELECT MAX(column_name) FROM table1

How do I dynamically set HTML5 data- attributes using react?

Note - if you want to pass a data attribute to a React Component, you need to handle them a little differently than other props.

2 options

Don't use camel case

<Option data-img-src='value' ... />

And then in the component, because of the dashes, you need to refer to the prop in quotes.

// @flow
class Option extends React.Component {

  props: {
    'data-img-src': string
  }

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props['data-img-src']} >...</option>
    )
  }
}

Or use camel case

<Option dataImgSrc='value' ... />

And then in the component, you need to convert.

// @flow
class Option extends React.Component {

  props: {
    dataImgSrc: string
  }

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props.dataImgSrc} >...</option>
    )
  }
}

Mainly just realize data- attributes and aria- attributes are treated specially. You are allowed to use hyphens in the attribute name in those two cases.

How can one grab a stack trace in C?

There is no platform independent way to do it.

The nearest thing you can do is to run the code without optimizations. That way you can attach to the process (using the visual c++ debugger or GDB) and get a usable stack trace.

How to indent/format a selection of code in Visual Studio Code with Ctrl + Shift + F

On OS X, choose "Document Format", and select all lines that you need format.

Then Option + Shift + F.

MySQL/Writing file error (Errcode 28)

For xampp users: on my experience, the problem was caused by a file, named '0' and located in the 'mysql' folder. The size was tooooo huge (mine exploded to about 256 Gb). Its removal fixed the problem.

Refresh image with a new one at the same url

I improved the script from AlexMA for showing my webcam on a web page wich periodically uploads a new image with the same name. I had issues that sometimes the image was flickering because of a broken image or not complete (up)loaded image. To prevent flickering I check the natural height of the image because the size of my webcam image did not change. Only if the loaded image height fits the original image height the full image will be shown on page.

  <h3>Webcam</h3>
  <p align="center">
    <img id="webcam" title="Webcam" onload="updateImage();" src="https://www.your-domain.com/webcam/current.jpg" alt="webcam image" width="900" border="0" />

    <script type="text/javascript" language="JavaScript">

    // off-screen image to preload next image
    var newImage = new Image();
    newImage.src = "https://www.your-domain.com/webcam/current.jpg";

    // remember the image height to prevent showing broken images
    var height = newImage.naturalHeight;

    function updateImage()
    {
        // for sure if the first image was a broken image
        if(newImage.naturalHeight > height)
        {
          height = newImage.naturalHeight;
        }

        // off-screen image loaded and the image was not broken
        if(newImage.complete && newImage.naturalHeight == height) 
        {
          // show the preloaded image on page
          document.getElementById("webcam").src = newImage.src;
        }

        // preload next image with cachebreaker
        newImage.src = "https://www.your-domain.com/webcam/current.jpg?time=" + new Date().getTime();

        // refresh image (set the refresh interval to half of webcam refresh, 
        // in my case the webcam refreshes every 5 seconds)
        setTimeout(updateImage, 2500);
    }

    </script>
</p>

Using generic std::function objects with member functions in one class

Unfortunately, C++ does not allow you to directly get a callable object referring to an object and one of its member functions. &Foo::doSomething gives you a "pointer to member function" which refers to the member function but not the associated object.

There are two ways around this, one is to use std::bind to bind the "pointer to member function" to the this pointer. The other is to use a lambda that captures the this pointer and calls the member function.

std::function<void(void)> f = std::bind(&Foo::doSomething, this);
std::function<void(void)> g = [this](){doSomething();};

I would prefer the latter.

With g++ at least binding a member function to this will result in an object three-pointers in size, assigning this to an std::function will result in dynamic memory allocation.

On the other hand, a lambda that captures this is only one pointer in size, assigning it to an std::function will not result in dynamic memory allocation with g++.

While I have not verified this with other compilers, I suspect similar results will be found there.

Hex-encoded String to Byte Array

I think what the questioner is after is converting the string representation of a hexadecimal value to a byte array representing that hexadecimal value.

The apache commons-codec has a class for that, Hex.

String s = "9B7D2C34A366BF890C730641E6CECF6F";    
byte[] bytes = Hex.decodeHex(s.toCharArray());

How to change css property using javascript

Consider the following example: If you want to change a single CSS property(say, color to 'blue'), then the below statement works fine.

document.getElementById("ele_id").style.color="blue";

But, for changing multiple properies the more robust way is using Object.assign() or, object spread operator {...};

See below:

const ele=document.getElementById("ele_id");
const custom_style={
    display: "block",
    color: "red"
}

//Object.assign():
Object.assign(ele.style,custum_style);

Spread operator works similarly, just the syntax is a little different.

Set order of columns in pandas dataframe

You can use this:

columnsTitles = ['onething', 'secondthing', 'otherthing']

frame = frame.reindex(columns=columnsTitles)

WCF Error - Could not find default endpoint element that references contract 'UserService.UserService'

Rename the output.config produced by svcutil.exe to app.config. it worked for me.

What reference do I need to use Microsoft.Office.Interop.Excel in .NET?

Make sure your project is 32 bit.

I had this problem, as soon as I ticked "Prefer 32 bit and rebuilt" all the Office Interop assemblies where available in Reference->Assemblies->Search "Office".

How does the data-toggle attribute work? (What's its API?)

The data-toggle attribute simple tell Bootstrap what exactly to do by giving it the name of the toggle action it is about to perform on a target element. If you specify collapse. It means bootstrap will collapse or uncollapse the element pointed by data-target of the action you clicked

Note: the target element must have the appropriate class for bootstrap to carry out the action

Source action:
data-toggle = collapse //type of toggle
data-target = #myDiv

Target:
class=collapse //I can collapse
id=myDiv

This is same for other type of toggle actions like tab, modal, dropdown

NodeJs : TypeError: require(...) is not a function

For me, I got similar error when switched between branches - one used newer ("typescriptish") version of @google-cloud/datastore packages which returns object with Datastore constructor as one of properties of exported object and I switched to other branch for a task, an older datastore version was used there, which exports Datastore constructor "directly" as module.exports value. I got the error because node_modules still had newer modules used by branch I switched from.

How do you change text to bold in Android?

Define a new style with the format you want in the style.xml file in the values folder

<style name="TextViewStyle" parent="AppBaseTheme">
    <item name="android:textStyle">bold</item>
    <item name="android:typeface">monospace</item>
    <item name="android:textSize">16sp</item>
    <item name="android:textColor">#5EADED</item>

</style>

Then apply this style to the TextView by writing the following code with the properties of the TextView

style="@style/TextViewStyle"

Reading string by char till end of line C/C++

You want to use single quotes:

if(c=='\0')

Double quotes (") are for strings, which are sequences of characters. Single quotes (') are for individual characters.

However, the end-of-line is represented by the newline character, which is '\n'.

Note that in both cases, the backslash is not part of the character, but just a way you represent special characters. Using backslashes you can represent various unprintable characters and also characters which would otherwise confuse the compiler.

Determining if an Object is of primitive type

I'm late to the show, but if you're testing a field, you can use getGenericType:

import static org.junit.Assert.*;

import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;

import org.junit.Test;

public class PrimitiveVsObjectTest {

    private static final Collection<String> PRIMITIVE_TYPES = 
            new HashSet<>(Arrays.asList("byte", "short", "int", "long", "float", "double", "boolean", "char"));

    private static boolean isPrimitive(Type type) {
        return PRIMITIVE_TYPES.contains(type.getTypeName());
    }

    public int i1 = 34;
    public Integer i2 = 34;

    @Test
    public void primitive_type() throws NoSuchFieldException, SecurityException {
        Field i1Field = PrimitiveVsObjectTest.class.getField("i1");
        Type genericType1 = i1Field.getGenericType();
        assertEquals("int", genericType1.getTypeName());
        assertNotEquals("java.lang.Integer", genericType1.getTypeName());
        assertTrue(isPrimitive(genericType1));
    }

    @Test
    public void object_type() throws NoSuchFieldException, SecurityException {
        Field i2Field = PrimitiveVsObjectTest.class.getField("i2");
        Type genericType2 = i2Field.getGenericType();
        assertEquals("java.lang.Integer", genericType2.getTypeName());
        assertNotEquals("int", genericType2.getTypeName());
        assertFalse(isPrimitive(genericType2));
    }
}

The Oracle docs list the 8 primitive types.

"A referral was returned from the server" exception when accessing AD from C#

I know this might sound silly, but I recently came across this myself, Make sure the domain controller is not read-only.

Storing data into list with class

This line is your problem:

lstemail.Add("JOhn","Smith","Los Angeles");

There is no direct cast from 3 strings to your custom class. The compiler has no way of figuring out what you're trying to do with this line. You need to Add() an instance of the class to lstemail:

lstemail.Add(new EmailData { FirstName = "JOhn", LastName = "Smith", Location = "Los Angeles" });

comparing elements of the same array in java

for (int i = 0; i < a.length; i++) {
    for (int k = 0; k < a.length; k++) {
        if (a[i] != a[k]) {
            System.out.println(a[i] + " not the same with  " + a[k + 1] + "\n");
        }
    }
}

You can start from k=1 & keep "a.length-1" in outer for loop, in order to reduce two comparisions,but that doesnt make any significant difference.

Can't access RabbitMQ web management interface after fresh install

If you are in Mac OS, you need to open the /usr/local/etc/rabbitmq/rabbitmq-env.conf and set NODE_IP_ADDRESS=, it used to be 127.0.0.1. Then add another user as the accepted answer suggested. After that, restart rabbitMQ, brew services restart rabbitmq

How to sort a List<Object> alphabetically using Object name field

From your code, it looks like your Comparator is already parameterized with Campaign. This will only work with List<Campaign>. Also, the method you're looking for is compareTo.

if (list.size() > 0) {
  Collections.sort(list, new Comparator<Campaign>() {
      @Override
      public int compare(final Campaign object1, final Campaign object2) {
          return object1.getName().compareTo(object2.getName());
      }
  });
}

Or if you are using Java 1.8

list
  .stream()
  .sorted((object1, object2) -> object1.getName().compareTo(object2.getName()));

One final comment -- there's no point in checking the list size. Sort will work on an empty list.

How do I convert csv file to rdd

Another alternative is to use the mapPartitionsWithIndex method as you'll get the partition index number and a list of all lines within that partition. Partition 0 and line 0 will be be the header

val rows = sc.textFile(path)
  .mapPartitionsWithIndex({ (index: Int, rows: Iterator[String]) => 
    val results = new ArrayBuffer[(String, Int)]

    var first = true
    while (rows.hasNext) {
      // check for first line
      if (index == 0 && first) {
        first = false
        rows.next // skip the first row
      } else {
        results += rows.next
      }
    }

    results.toIterator
}, true)

rows.flatMap { row => row.split(",") }

how to check redis instance version?

To support the answers given above, The details of the redis instance can be obtained by

$ redis-cli
$ INFO

This gives all the info you may need

# Server
redis_version:5.0.5
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:da75abdfe06a50f8
redis_mode:standalone
os:Linux 5.3.0-51-generic x86_64
arch_bits:64
multiplexing_api:epoll
atomicvar_api:atomic-builtin
gcc_version:7.5.0
process_id:14126
run_id:adfaeec5683d7381a2a175a2111f6159b6342830
tcp_port:6379
uptime_in_seconds:16860
uptime_in_days:0
hz:10
configured_hz:10
lru_clock:15766886
executable:/tmp/redis-5.0.5/src/redis-server
config_file:

# Clients
connected_clients:22
....More Verbose

The version lies in the second line :)

What is the difference between `new Object()` and object literal notation?

2019 Update

I ran the same code as @rjloura on my OSX High Sierra 10.13.6 node version 10.13.0 and these are the results

console.log('Testing Array:');
console.time('using[]');
for(var i=0; i<200000000; i++){var arr = []};
console.timeEnd('using[]');

console.time('using new');
for(var i=0; i<200000000; i++){var arr = new Array};
console.timeEnd('using new');

console.log('Testing Object:');

console.time('using{}');
for(var i=0; i<200000000; i++){var obj = {}};
console.timeEnd('using{}');

console.time('using new');
for(var i=0; i<200000000; i++){var obj = new Object};
console.timeEnd('using new');


Testing Array:
using[]: 117.613ms
using new: 117.168ms
Testing Object:
using{}: 117.205ms
using new: 118.644ms

How to convert seconds to time format?

If You want nice format like: 0:00:00 use str_pad() as @Gardner.

Iterating through a string word by word

s = 'hi how are you'
l = list(map(lambda x: x,s.split()))
print(l)

Output: ['hi', 'how', 'are', 'you']

How to install popper.js with Bootstrap 4?

I had problems installing it Bootstrap as well, so I did:

Install popper.js: npm install popper.js@^1.12.3 --save

Install jQuery: npm install [email protected] --save

Then I had a high severity vulnerability message when installing [email protected] and got this message:

run npm audit fix to fix them, or npm audit for details

So I did npm audit fix, and after another npm audit fix --force it successfully installed!

Find kth smallest element in a binary search tree in Optimum way

Python Solution Time Complexity : O(n) Space Complexity : O(1)

Idea is to use Morris Inorder Traversal

class Solution(object):
def inorderTraversal(self, current , k ):
    while(current is not None):    #This Means we have reached Right Most Node i.e end of LDR traversal

        if(current.left is not None):  #If Left Exists traverse Left First
            pre = current.left   #Goal is to find the node which will be just before the current node i.e predecessor of current node, let's say current is D in LDR goal is to find L here
            while(pre.right is not None and pre.right != current ): #Find predecesor here
                pre = pre.right
            if(pre.right is None):  #In this case predecessor is found , now link this predecessor to current so that there is a path and current is not lost
                pre.right = current
                current = current.left
            else:                   #This means we have traverse all nodes left to current so in LDR traversal of L is done
                k -= 1
                if(k == 0):
                    return current.val
                pre.right = None       #Remove the link tree restored to original here 
                current = current.right
        else:               #In LDR  LD traversal is done move to R 
            k -= 1
            if(k == 0):
                return current.val
            current = current.right

    return 0

def kthSmallest(self, root, k):
    return self.inorderTraversal( root , k  )

Check if an object belongs to a class in Java

I agree with the use of instanceof already mentioned.

An additional benefit of using instanceof is that when used with a null reference instanceof of will return false, while a.getClass() would throw a NullPointerException.

Use dynamic (variable) string as regex pattern in JavaScript

You don't need the " to define a regular expression so just:

var regex = /(?!(?:[^<]+>|[^>]+<\/a>))\b(value)\b/is; // this is valid syntax

If value is a variable and you want a dynamic regular expression then you can't use this notation; use the alternative notation.

String.replace also accepts strings as input, so you can do "fox".replace("fox", "bear");

Alternative:

var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(value)\b/", "is");
var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(" + value + ")\b/", "is");
var regex = new RegExp("/(?!(?:[^<]+>|[^>]+<\/a>))\b(.*?)\b/", "is");

Keep in mind that if value contains regular expressions characters like (, [ and ? you will need to escape them.

Sending email from Azure

If you're looking for some ESP alternatives, you should have a look at Mailjet for Microsoft Azure too! As a global email service and infrastructure provider, they enable you to send, deliver and track transactional and marketing emails via their APIs, SMTP Relay or UI all from one single platform, thought both for developers and emails owners.

Disclaimer: I’m working at Mailjet as a Developer Evangelist.

jQuery UI 1.10: dialog and zIndex option

Add zIndex property to dialog object:

$(elm).dialog(
 zIndex: 10000
);

Resetting Select2 value in dropdown with reset button

What I found works well is as follows:

if you have a placeholder option like 'All' or '-Select-' and its the first option and that's that you want to set the value to when you 'reset' you can use

$('#id').select2('val',0);

0 is essentially the option that you want to set it to on reset. If you want to set it to the last option then get the length of options and set it that length - 1. Basically use the index of whatever option you want to set the select2 value to on reset.

If you don't have a placeholder and just want no text to appear in the field use:

$('#id').select2('val','');

How do I remove my IntelliJ license in 2019.3?

To remove the license key:

  1. Find the IntelliJ configuration directory
  2. Find the .key license file
  3. Remove or rename the .key license file

In my case on a Windows 7 machine I could find this license key in C:\Users\you\.IntelliJIdea13\config\idea13.key

How to select an element inside "this" in jQuery?

$( this ).find( 'li.target' ).css("border", "3px double red");

or

$( this ).children( 'li.target' ).css("border", "3px double red");

Use children for immediate descendants, or find for deeper elements.

Trying Gradle build - "Task 'build' not found in root project"

run

gradle clean 

then try

gradle build 

it worked for me

Why is there still a row limit in Microsoft Excel?

Probably because of optimizations. Excel 2007 can have a maximum of 16 384 columns and 1 048 576 rows. Strange numbers?

14 bits = 16 384, 20 bits = 1 048 576

14 + 20 = 34 bits = more than one 32 bit register can hold.

But they also need to store the format of the cell (text, number etc) and formatting (colors, borders etc). Assuming they use two 32-bit words (64 bit) they use 34 bits for the cell number and have 30 bits for other things.

Why is that important? In memory they don't need to allocate all the memory needed for the whole spreadsheet but only the memory necessary for your data, and every data is tagged with in what cell it is supposed to be in.

Update 2016:

Found a link to Microsoft's specification for Excel 2013 & 2016

  • Open workbooks: Limited by available memory and system resources
  • Worksheet size: 1,048,576 rows (20 bits) by 16,384 columns (14 bits)
  • Column width: 255 characters (8 bits)
  • Row height: 409 points
  • Page breaks: 1,026 horizontal and vertical (unexpected number, probably wrong, 10 bits is 1024)
  • Total number of characters that a cell can contain: 32,767 characters (signed 16 bits)
  • Characters in a header or footer: 255 (8 bits)
  • Sheets in a workbook: Limited by available memory (default is 1 sheet)
  • Colors in a workbook: 16 million colors (32 bit with full access to 24 bit color spectrum)
  • Named views in a workbook: Limited by available memory
  • Unique cell formats/cell styles: 64,000 (16 bits = 65536)
  • Fill styles: 256 (8 bits)
  • Line weight and styles: 256 (8 bits)
  • Unique font types: 1,024 (10 bits) global fonts available for use; 512 per workbook
  • Number formats in a workbook: Between 200 and 250, depending on the language version of Excel that you have installed
  • Names in a workbook: Limited by available memory
  • Windows in a workbook: Limited by available memory
  • Hyperlinks in a worksheet: 66,530 hyperlinks (unexpected number, probably wrong. 16 bits = 65536)
  • Panes in a window: 4
  • Linked sheets: Limited by available memory
  • Scenarios: Limited by available memory; a summary report shows only the first 251 scenarios
  • Changing cells in a scenario: 32
  • Adjustable cells in Solver: 200
  • Custom functions: Limited by available memory
  • Zoom range: 10 percent to 400 percent
  • Reports: Limited by available memory
  • Sort references: 64 in a single sort; unlimited when using sequential sorts
  • Undo levels: 100
  • Fields in a data form: 32
  • Workbook parameters: 255 parameters per workbook
  • Items displayed in filter drop-down lists: 10,000

What does Python's socket.recv() return for non-blocking sockets if no data is received until a timeout occurs?

It is simple: if recv() returns 0 bytes; you will not receive any more data on this connection. Ever. You still might be able to send.

It means that your non-blocking socket have to raise an exception (it might be system-dependent) if no data is available but the connection is still alive (the other end may send).

Recording video feed from an IP camera over a network

Why don't you consider www.cameraftp.com? it supports image upload and online viewer

How do I convert Int/Decimal to float in C#?

It is just:

float f = (float)6;

"X does not name a type" error in C++

You need to define MyMessageBox before User -- because User include object of MyMessageBox by value (and so compiler should know its size).

Also you'll need to forward declare User befor MyMessageBox -- because MyMessageBox include member of User* type.

What's the best free C++ profiler for Windows?

Please try my profiler, called cRunWatch. It is just two files, so it is easy to integrate with your projects, and requires adding exactly one line to instrument a piece of code.

http://ravenspoint.wordpress.com/2010/06/16/timing/

Requires the Boost library.

Bootstrap - Removing padding or margin when screen size is smaller

The easy solution is to write something like that,

px-lg-1

mb-lg-5

By adding lg, the class will be applied only on large screens

'AND' vs '&&' as operator

Precedence differs between && and and (&& has higher precedence than and), something that causes confusion when combined with a ternary operator. For instance,

$predA && $predB ? "foo" : "bar"

will return a string whereas

$predA and $predB ? "foo" : "bar"

will return a boolean.

Difference between Big-O and Little-O Notation

In general

Asymptotic notation is something you can understand as: how do functions compare when zooming out? (A good way to test this is simply to use a tool like Desmos and play with your mouse wheel). In particular:

  • f(n) ? o(n) means: at some point, the more you zoom out, the more f(n) will be dominated by n (it will progressively diverge from it).
  • g(n) ? T(n) means: at some point, zooming out will not change how g(n) compare to n (if we remove ticks from the axis you couldn't tell the zoom level).

Finally h(n) ? O(n) means that function h can be in either of these two categories. It can either look a lot like n or it could be smaller and smaller than n when n increases. Basically, both f(n) and g(n) are also in O(n).

In computer science

In computer science, people will usually prove that a given algorithm admits both an upper O and a lower bound . When both bounds meet that means that we found an asymptotically optimal algorithm to solve that particular problem.

For example, if we prove that the complexity of an algorithm is both in O(n) and (n) it implies that its complexity is in T(n). That's the definition of T and it more or less translates to "asymptotically equal". Which also means that no algorithm can solve the given problem in o(n). Again, roughly saying "this problem can't be solved in less than n steps".

An upper bound of O(n) simply means that even in the worse case, the algorithm will terminate in at most n steps (ignoring all constant factors, both multiplicative and additive). A lower bound of (n) means on the opposite that we built some examples where the problem solved by this algorithm couldn't be solved in less than n steps (again ignoring multiplicative and additive constants). The number of steps is at most n and at least n so this problem complexity is "exactly n". Instead of saying "ignoring constant multiplicative/additive factor" every time we just write T(n) for short.

How to check if a column exists in Pandas

To check if one or more columns all exist, you can use set.issubset, as in:

if set(['A','C']).issubset(df.columns):
   df['sum'] = df['A'] + df['C']                

As @brianpck points out in a comment, set([]) can alternatively be constructed with curly braces,

if {'A', 'C'}.issubset(df.columns):

See this question for a discussion of the curly-braces syntax.

Or, you can use a list comprehension, as in:

if all([item in df.columns for item in ['A','C']]):

jQuery '.each' and attaching '.click' event

No need to use .each. click already binds to all div occurrences.

$('div').click(function(e) {
    ..    
});

See Demo

Note: use hard binding such as .click to make sure dynamically loaded elements don't get bound.

Selecting fields from JSON output

Assume you stored that dictionary in a variable called values. To get id in to a variable, do:

idValue = values['criteria'][0]['id']

If that json is in a file, do the following to load it:

import json
jsonFile = open('your_filename.json', 'r')
values = json.load(jsonFile)
jsonFile.close()

If that json is from a URL, do the following to load it:

import urllib, json
f = urllib.urlopen("http://domain/path/jsonPage")
values = json.load(f)
f.close()

To print ALL of the criteria, you could:

for criteria in values['criteria']:
    for key, value in criteria.iteritems():
        print key, 'is:', value
    print ''

What is the time complexity of indexing, inserting and removing from common data structures?

Information on this topic is now available on Wikipedia at: Search data structure

+----------------------+----------+------------+----------+--------------+
|                      |  Insert  |   Delete   |  Search  | Space Usage  |
+----------------------+----------+------------+----------+--------------+
| Unsorted array       | O(1)     | O(1)       | O(n)     | O(n)         |
| Value-indexed array  | O(1)     | O(1)       | O(1)     | O(n)         |
| Sorted array         | O(n)     | O(n)       | O(log n) | O(n)         |
| Unsorted linked list | O(1)*    | O(1)*      | O(n)     | O(n)         |
| Sorted linked list   | O(n)*    | O(1)*      | O(n)     | O(n)         |
| Balanced binary tree | O(log n) | O(log n)   | O(log n) | O(n)         |
| Heap                 | O(log n) | O(log n)** | O(n)     | O(n)         |
| Hash table           | O(1)     | O(1)       | O(1)     | O(n)         |
+----------------------+----------+------------+----------+--------------+

 * The cost to add or delete an element into a known location in the list 
   (i.e. if you have an iterator to the location) is O(1). If you don't 
   know the location, then you need to traverse the list to the location
   of deletion/insertion, which takes O(n) time. 

** The deletion cost is O(log n) for the minimum or maximum, O(n) for an
   arbitrary element.

String escape into XML

Thanks to @sehe for the one-line escape:

var escaped = new System.Xml.Linq.XText(unescaped).ToString();

I add to it the one-line un-escape:

var unescapedAgain = System.Xml.XmlReader.Create(new StringReader("<r>" + escaped + "</r>")).ReadElementString();

Making a div vertically scrollable using CSS

Well the above answers have give a good explanations to half of the question. For the other half.

Why don't just hide the scroll bar itself. This way it will look more appealing as most of the people ( including me ) hate the scroll bar. You can use this code

::-webkit-scrollbar {
    width: 0px;  /* Remove scrollbar space */
    background: transparent;  /* Optional: just make scrollbar invisible */
}

Python, TypeError: unhashable type: 'list'

The problem is that you can't use a list as the key in a dict, since dict keys need to be immutable. Use a tuple instead.

This is a list:

[x, y]

This is a tuple:

(x, y)

Note that in most cases, the ( and ) are optional, since , is what actually defines a tuple (as long as it's not surrounded by [] or {}, or used as a function argument).

You might find the section on tuples in the Python tutorial useful:

Though tuples may seem similar to lists, they are often used in different situations and for different purposes. Tuples are immutable, and usually contain an heterogeneous sequence of elements that are accessed via unpacking (see later in this section) or indexing (or even by attribute in the case of namedtuples). Lists are mutable, and their elements are usually homogeneous and are accessed by iterating over the list.

And in the section on dictionaries:

Unlike sequences, which are indexed by a range of numbers, dictionaries are indexed by keys, which can be any immutable type; strings and numbers can always be keys. Tuples can be used as keys if they contain only strings, numbers, or tuples; if a tuple contains any mutable object either directly or indirectly, it cannot be used as a key. You can’t use lists as keys, since lists can be modified in place using index assignments, slice assignments, or methods like append() and extend().


In case you're wondering what the error message means, it's complaining because there's no built-in hash function for lists (by design), and dictionaries are implemented as hash tables.

How to push both value and key into PHP array

I wrote a simple function:

function push(&$arr,$new) {
    $arr = array_merge($arr,$new);
}

so that I can "upsert" new element easily:

push($my_array, ['a'=>1,'b'=>2])

How to append strings using sprintf?

I find the following method works nicely.

sprintf(Buffer,"Hello World");
sprintf(&Buffer[strlen[Buffer]],"Good Morning");
sprintf(&Buffer[strlen[Buffer]],"Good Afternoon");

Partly cherry-picking a commit with Git

If you want to specify a list of files on the command line, and get the whole thing done in a single atomic command, try:

git apply --3way <(git show -- list-of-files)

--3way: If a patch does not apply cleanly, Git will create a merge conflict so you can run git mergetool. Omitting --3way will make Git give up on patches which don't apply cleanly.

CSS table-cell equal width

This can be done by setting table-cell style to width: auto, and content empty. The columns are now equal-wide, but holding no content.

To insert content to the cell, add an div with css:

position: absolute;
left: 0;
top: 0;
right: 0;
bottom: 0;

You also need to add position: relative to the cells.

Now you can put the actual content into the div talked above.

https://jsfiddle.net/vensdvvb/

Gradient of n colors ranging from color 1 and color 2

The above answer is useful but in graphs, it is difficult to distinguish between darker gradients of black. One alternative I found is to use gradients of gray colors as follows

palette(gray.colors(10, 0.9, 0.4))
plot(rep(1,10),col=1:10,pch=19,cex=3))

More info on gray scale here.

Added

When I used the code above for different colours like blue and black, the gradients were not that clear. heat.colors() seems more useful.

This document has more detailed information and options. pdf

How do I implement basic "Long Polling"?

I've got a really simple chat example as part of slosh.

Edit: (since everyone's pasting their code in here)

This is the complete JSON-based multi-user chat using long-polling and slosh. This is a demo of how to do the calls, so please ignore the XSS problems. Nobody should deploy this without sanitizing it first.

Notice that the client always has a connection to the server, and as soon as anyone sends a message, everyone should see it roughly instantly.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Copyright (c) 2008 Dustin Sallings <[email protected]> -->
<html lang="en">
  <head>
    <title>slosh chat</title>
    <script type="text/javascript"
      src="http://code.jquery.com/jquery-latest.js"></script>
    <link title="Default" rel="stylesheet" media="screen" href="style.css" />
  </head>

  <body>
    <h1>Welcome to Slosh Chat</h1>

    <div id="messages">
      <div>
        <span class="from">First!:</span>
        <span class="msg">Welcome to chat. Please don't hurt each other.</span>
      </div>
    </div>

    <form method="post" action="#">
      <div>Nick: <input id='from' type="text" name="from"/></div>
      <div>Message:</div>
      <div><textarea id='msg' name="msg"></textarea></div>
      <div><input type="submit" value="Say it" id="submit"/></div>
    </form>

    <script type="text/javascript">
      function gotData(json, st) {
        var msgs=$('#messages');
        $.each(json.res, function(idx, p) {
          var from = p.from[0]
          var msg = p.msg[0]
          msgs.append("<div><span class='from'>" + from + ":</span>" +
            " <span class='msg'>" + msg + "</span></div>");
        });
        // The jQuery wrapped msgs above does not work here.
        var msgs=document.getElementById("messages");
        msgs.scrollTop = msgs.scrollHeight;
      }

      function getNewComments() {
        $.getJSON('/topics/chat.json', gotData);
      }

      $(document).ready(function() {
        $(document).ajaxStop(getNewComments);
        $("form").submit(function() {
          $.post('/topics/chat', $('form').serialize());
          return false;
        });
        getNewComments();
      });
    </script>
  </body>
</html>

Date object to Calendar [Java]

Calendar.setTime()

It's often useful to look at the signature and description of API methods, not just their name :) - Even in the Java standard API, names can sometimes be misleading.

Java: Calculating the angle between two points in degrees

What about something like :

angle = angle % 360;

Applying Comic Sans Ms font style

The font may exist with different names, and not at all on some systems, so you need to use different variations and fallback to get the closest possible look on all systems:

font-family: "Comic Sans MS", "Comic Sans", cursive;

Be careful what you use this font for, though. Many consider it as ugly and overused, so it should not be use for something that should look professional.

Get int value from enum in C#

Maybe I missed it, but has anyone tried a simple generic extension method?

This works great for me. You can avoid the type cast in your API this way but ultimately it results in a change type operation. This is a good case for programming Roslyn to have the compiler make a GetValue<T> method for you.

    public static void Main()
    {
        int test = MyCSharpWrapperMethod(TestEnum.Test1);

        Debug.Assert(test == 1);
    }

    public static int MyCSharpWrapperMethod(TestEnum customFlag)
    {
        return MyCPlusPlusMethod(customFlag.GetValue<int>());
    }

    public static int MyCPlusPlusMethod(int customFlag)
    {
        // Pretend you made a PInvoke or COM+ call to C++ method that require an integer
        return customFlag;
    }

    public enum TestEnum
    {
        Test1 = 1,
        Test2 = 2,
        Test3 = 3
    }
}

public static class EnumExtensions
{
    public static T GetValue<T>(this Enum enumeration)
    {
        T result = default(T);

        try
        {
            result = (T)Convert.ChangeType(enumeration, typeof(T));
        }
        catch (Exception ex)
        {
            Debug.Assert(false);
            Debug.WriteLine(ex);
        }

        return result;
    }
}

How to get current date time in milliseconds in android

The problem is that System. currentTimeMillis(); returns the number of milliseconds from 1970-01-01T00:00:00Z, but new Date() gives the current local time. Adding the ZONE_OFFSET and DST_OFFSET from the Calendar class gives you the time in UTC.

Calendar rightNow = Calendar.getInstance();

// offset to add since we're not UTC

long offset = rightNow.get(Calendar.ZONE_OFFSET) +
    rightNow.get(Calendar.DST_OFFSET);

long sinceMidnight = (rightNow.getTimeInMillis() + offset) %
    (24 * 60 * 60 * 1000);

System.out.println(sinceMidnight + " milliseconds since midnight");

Java, Check if integer is multiple of a number

//More Efficiently
public class Multiples {
    public static void main(String[]args) {

        int j = 5;

        System.out.println(j % 4 == 0);

    }
}

Simulate a button click in Jest

Additionally to the solutions that were suggested in sibling comments, you may change your testing approach a little bit and test not the whole page all at once (with a deep children components tree), but do an isolated component testing. This will simplify testing of onClick() and similar events (see example below).

The idea is to test only one component at a time and not all of them together. In this case all children components will be mocked using the jest.mock() function.

Here is an example of how the onClick() event may be tested in an isolated SearchForm component using Jest and react-test-renderer.

import React from 'react';
import renderer from 'react-test-renderer';
import { SearchForm } from '../SearchForm';

describe('SearchForm', () => {
  it('should fire onSubmit form callback', () => {
    // Mock search form parameters.
    const searchQuery = 'kittens';
    const onSubmit = jest.fn();

    // Create test component instance.
    const testComponentInstance = renderer.create((
      <SearchForm query={searchQuery} onSearchSubmit={onSubmit} />
    )).root;

    // Try to find submit button inside the form.
    const submitButtonInstance = testComponentInstance.findByProps({
      type: 'submit',
    });
    expect(submitButtonInstance).toBeDefined();

    // Since we're not going to test the button component itself
    // we may just simulate its onClick event manually.
    const eventMock = { preventDefault: jest.fn() };
    submitButtonInstance.props.onClick(eventMock);

    expect(onSubmit).toHaveBeenCalledTimes(1);
    expect(onSubmit).toHaveBeenCalledWith(searchQuery);
  });
});

how to get the cookies from a php curl into a variable

$ch = curl_init('http://www.google.com/');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
// get headers too with this line
curl_setopt($ch, CURLOPT_HEADER, 1);
$result = curl_exec($ch);
// get cookie
// multi-cookie variant contributed by @Combuster in comments
preg_match_all('/^Set-Cookie:\s*([^;]*)/mi', $result, $matches);
$cookies = array();
foreach($matches[1] as $item) {
    parse_str($item, $cookie);
    $cookies = array_merge($cookies, $cookie);
}
var_dump($cookies);

How can I do factory reset using adb in android?

Warning

From @sidharth: "caused my lava iris alfa to go into a bootloop :("


For my Motorola Nexus 6 running Android Marshmallow 6.0.1 I did:

adb devices       # Check the phone is running
adb reboot bootloader
# Wait a few seconds
fastboot devices  # Check the phone is in bootloader
fastboot -w       # Wipe user data

How to programmatically close a JFrame

This examples shows how to realize the confirmed window close operation.

The window has a Window adapter which switches the default close operation to EXIT_ON_CLOSEor DO_NOTHING_ON_CLOSE dependent on your answer in the OptionDialog.

The method closeWindow of the ConfirmedCloseWindow fires a close window event and can be used anywhere i.e. as an action of an menu item

public class WindowConfirmedCloseAdapter extends WindowAdapter {

    public void windowClosing(WindowEvent e) {

        Object options[] = {"Yes", "No"};

        int close = JOptionPane.showOptionDialog(e.getComponent(),
                "Really want to close this application?\n", "Attention",
                JOptionPane.YES_NO_OPTION,
                JOptionPane.INFORMATION_MESSAGE,
                null,
                options,
                null);

        if(close == JOptionPane.YES_OPTION) {
           ((JFrame)e.getSource()).setDefaultCloseOperation(
                   JFrame.EXIT_ON_CLOSE);
        } else {
           ((JFrame)e.getSource()).setDefaultCloseOperation(
                   JFrame.DO_NOTHING_ON_CLOSE);
        }
    }
}

public class ConfirmedCloseWindow extends JFrame {

    public ConfirmedCloseWindow() {

        addWindowListener(new WindowConfirmedCloseAdapter());
    }

    private void closeWindow() {
        processWindowEvent(new WindowEvent(this, WindowEvent.WINDOW_CLOSING));
    }
}

Makefile: How to correctly include header file and its directory?

The preprocessor is looking for StdCUtil/split.h in

and in

  • $INC_DIR (i.e. ../StdCUtil/ = /root/Core/../StdCUtil/ = /root/StdCUtil/). So ../StdCUtil/ + StdCUtil/split.h = ../StdCUtil/StdCUtil/split.h and the file is missing

You can fix the error changing the $INC_DIR variable (best solution):

$INC_DIR = ../

or the include directive:

#include "split.h"

but in this way you lost the "path syntax" that makes it very clear what namespace or module the header file belongs to.

Reference:

EDIT/UPDATE

It should also be

CXX = g++
CXXFLAGS = -c -Wall -I$(INC_DIR)

...

%.o: %.cpp $(DEPS)
    $(CXX) -o $@ $< $(CXXFLAGS)

How can I get CMake to find my alternative Boost installation?

After digging around in CMake and experimenting, I determined that CMake was unhappy with the fact that all of my Boost libraries were contained in /usr/local/lib/boost and not /usr/local/lib. Once I soft-linked them back out, the build worked.

How to ignore PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException?

I have used the below code to override the SSL checking in my project and it worked for me.

package com.beingjavaguys.testftp;

import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.cert.X509Certificate;

/**
 * Fix for Exception in thread "main" javax.net.ssl.SSLHandshakeException:
 * sun.security.validator.ValidatorException: PKIX path building failed:
 * sun.security.provider.certpath.SunCertPathBuilderException: unable to find
 * valid certification path to requested target
 */
public class ConnectToHttpsUrl {
    public static void main(String[] args) throws Exception {
        /* Start of Fix */
        TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
            public java.security.cert.X509Certificate[] getAcceptedIssuers() { return null; }
            public void checkClientTrusted(X509Certificate[] certs, String authType) { }
            public void checkServerTrusted(X509Certificate[] certs, String authType) { }

        } };

        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, new java.security.SecureRandom());
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());

        // Create all-trusting host name verifier
        HostnameVerifier allHostsValid = new HostnameVerifier() {
            public boolean verify(String hostname, SSLSession session) { return true; }
        };
        // Install the all-trusting host verifier
        HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);
        /* End of the fix*/

        URL url = new URL("https://nameofthesecuredurl.com");
        URLConnection con = url.openConnection();
        Reader reader = new InputStreamReader(con.getInputStream());
        while (true) {
            int ch = reader.read();
            if (ch == -1) 
                break;
            System.out.print((char) ch);
        }
    }
}

VIM Disable Automatic Newline At End Of File

And for vim 7.4+ you can use (preferably on your .vimrc) (thanks to ??? for that last bit of news!):

:set nofixendofline

Now regarding older versions of vim.

Even if the file was already saved with new lines at the end:

vim -b file and once in vim:

:set noeol
:wq

done.

alternatively you can open files in vim with :e ++bin file

Yet another alternative:

:set binary
:set noeol
:wq

see more details at Why do I need vim in binary mode for 'noeol' to work?

android studio 0.4.2: Gradle project sync failed error

For those who are upgrading to v1.0 of Android Studio and see the error Gradle DSL method not found: 'runProguard', If you are using version 0.14.0 or higher of the gradle plugin, you should replace "runProguard" with "minifyEnabled" in your build.gradle files. i.e.

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
    }
}

How to avoid annoying error "declared and not used"

In case others have a hard time making sense of this, I think it might help to explain it in very straightforward terms. If you have a variable that you don't use, for example a function for which you've commented out the invocation (a common use-case):

myFn := func () { }
// myFn()

You can assign a useless/blank variable to the function so that it's no longer unused:

myFn := func () { }
_ = myFn
// myFn()

Rearrange columns using cut

You may also combine cut and paste:

paste <(cut -f2 file.txt) <(cut -f1 file.txt)

via comments: It's possible to avoid bashisms and remove one instance of cut by doing:

paste file.txt file.txt | cut -f2,3

Relative instead of Absolute paths in Excel VBA

Just to clarify what yalestar said, this will give you the relative path:

Workbooks.Open FileName:= ThisWorkbook.Path & "\TRICATEndurance Summary.html"

Evaluate empty or null JSTL c tags

to also check blank string, I suggest following

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<c:if test="${empty fn:trim(var1)}">

</c:if>

It also handles nulls

Concatenate a list of pandas dataframes together

Given that all the dataframes have the same columns, you can simply concat them:

import pandas as pd
df = pd.concat(list_of_dataframes)

Using setattr() in python

Setattr: We use setattr to add an attribute to our class instance. We pass the class instance, the attribute name, and the value. and with getattr we retrive these values

For example

Employee = type("Employee", (object,), dict())

employee = Employee()

# Set salary to 1000
setattr(employee,"salary", 1000 )

# Get the Salary
value = getattr(employee, "salary")

print(value)

How to stretch children to fill cross-axis?

  • The children of a row-flexbox container automatically fill the container's vertical space.

  • Specify flex: 1; for a child if you want it to fill the remaining horizontal space:

_x000D_
_x000D_
.wrapper {_x000D_
  display: flex;_x000D_
  flex-direction: row;_x000D_
  align-items: stretch;_x000D_
  width: 100%;_x000D_
  height: 5em;_x000D_
  background: #ccc;_x000D_
}_x000D_
.wrapper > .left_x000D_
{_x000D_
  background: #fcc;_x000D_
}_x000D_
.wrapper > .right_x000D_
{_x000D_
  background: #ccf;_x000D_
  flex: 1; _x000D_
}
_x000D_
<div class="wrapper">_x000D_
  <div class="left">Left</div>_x000D_
  <div class="right">Right</div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

  • Specify flex: 1; for both children if you want them to fill equal amounts of the horizontal space:

_x000D_
_x000D_
.wrapper {_x000D_
  display: flex;_x000D_
  flex-direction: row;_x000D_
  align-items: stretch;_x000D_
  width: 100%;_x000D_
  height: 5em;_x000D_
  background: #ccc;_x000D_
}_x000D_
.wrapper > div _x000D_
{_x000D_
  flex: 1; _x000D_
}_x000D_
.wrapper > .left_x000D_
{_x000D_
  background: #fcc;_x000D_
}_x000D_
.wrapper > .right_x000D_
{_x000D_
  background: #ccf;_x000D_
}
_x000D_
<div class="wrapper">_x000D_
  <div class="left">Left</div>_x000D_
  <div class="right">Right</div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

Python NLTK: SyntaxError: Non-ASCII character '\xc3' in file (Sentiment Analysis -NLP)

Add the following to the top of your file # coding=utf-8

If you go to the link in the error you can seen the reason why:

Defining the Encoding

Python will default to ASCII as standard encoding if no other encoding hints are given. To define a source code encoding, a magic comment must be placed into the source files either as first or second line in the file, such as: # coding=

how to check if a datareader is null or empty

First of all, you probably want to check for a DBNull not a regular Null.

Or you could look at the IsDBNull method

SQL Server: Best way to concatenate multiple columns?

If the fields are nullable, then you'll have to handle those nulls. Remember that null is contagious, and concat('foo', null) simply results in NULL as well:

SELECT CONCAT(ISNULL(column1, ''),ISNULL(column2,'')) etc...

Basically test each field for nullness, and replace with an empty string if so.

How to pass parameters to a modal?

If you're not using AngularJS UI Bootstrap, here's how I did it.

I created a directive that will hold that entire element of your modal, and recompile the element to inject your scope into it.

angular.module('yourApp', []).
directive('myModal',
       ['$rootScope','$log','$compile',
function($rootScope,  $log,  $compile) {
    var _scope = null;
    var _element = null;
    var _onModalShow = function(event) {
        _element.after($compile(event.target)(_scope));
    };

    return {
        link: function(scope, element, attributes) {
            _scope = scope;
            _element = element;
            $(element).on('show.bs.modal',_onModalShow);
        }
    };
}]);

I'm assuming your modal template is inside the scope of your controller, then add directive my-modal to your template. If you saved the clicked user to $scope.aModel, the original template will now work.

Note: The entire scope is now visible to your modal so you can also access $scope.users in it.

<div my-modal id="encouragementModal" class="modal hide fade">
  <div class="modal-header">
    <button type="button" class="close" data-dismiss="modal"
      aria-hidden="true">&times;</button>
    <h3>Confirm encouragement?</h3>
  </div>
  <div class="modal-body">
      Do you really want to encourage <b>{{aModel.userName}}</b>?
  </div>
  <div class="modal-footer">
    <button class="btn btn-info"
      ng-click="encourage('${createLink(uri: '/encourage/')}',{{aModel.userName}})">
      Confirm
    </button>
    <button class="btn" data-dismiss="modal" aria-hidden="true">Never Mind</button>
  </div>
</div>

How to scroll to the bottom of a RecyclerView? scrollToPosition doesn't work

When you call setAdapter, that does not immediately lay out and position items on the screen (that takes a single layout pass) hence your scrollToPosition() call has no actual elements to scroll to when you call it.

Instead, you should register a ViewTreeObserver.OnGlobalLayoutListener (via addOnGlobalLayoutListner() from a ViewTreeObserver created by conversationView.getViewTreeObserver()) which delays your scrollToPosition() until after the first layout pass:

conversationView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
  public void onGlobalLayout() {
    conversationView.scrollToPosition(GENERIC_MESSAGE_LIST.size();
    // Unregister the listener to only call scrollToPosition once
    conversationView.getViewTreeObserver().removeGlobalOnLayoutListener(this);

    // Use vto.removeOnGlobalLayoutListener(this) on API16+ devices as 
    // removeGlobalOnLayoutListener is deprecated.
    // They do the same thing, just a rename so your choice.
  }
});

Why can't I do <img src="C:/localfile.jpg">?

Newtang's observation about the security rules aside, how are you going to know that anyone who views your page will have the correct images at c:\localfile.jpg? You can't. Even if you think you can, you can't. It presupposes a windows environment, for one thing.

TypeError: Converting circular structure to JSON in nodejs

JSON doesn't accept circular objects - objects which reference themselves. JSON.stringify() will throw an error if it comes across one of these.

The request (req) object is circular by nature - Node does that.

In this case, because you just need to log it to the console, you can use the console's native stringifying and avoid using JSON:

console.log("Request data:");
console.log(req);

BackgroundWorker vs background Thread

I knew how to use threads before I knew .NET, so it took some getting used to when I began using BackgroundWorkers. Matt Davis has summarized the difference with great excellence, but I would add that it's more difficult to comprehend exactly what the code is doing, and this can make debugging harder. It's easier to think about creating and shutting down threads, IMO, than it is to think about giving work to a pool of threads.

I still can't comment other people's posts, so forgive my momentary lameness in using an answer to address piers7

Don't use Thread.Abort(); instead, signal an event and design your thread to end gracefully when signaled. Thread.Abort() raises a ThreadAbortException at an arbitrary point in the thread's execution, which can do all kinds of unhappy things like orphan Monitors, corrupt shared state, and so on.
http://msdn.microsoft.com/en-us/library/system.threading.thread.abort.aspx

Python OpenCV2 (cv2) wrapper to get image size?

import cv2
img=cv2.imread('my_test.jpg')
img_info = img.shape
print("Image height :",img_info[0])
print("Image Width :", img_info[1])
print("Image channels :", img_info[2])

Ouput :- enter image description here

My_test.jpg link ---> https://i.pinimg.com/originals/8b/ca/f5/8bcaf5e60433070b3210431e9d2a9cd9.jpg

What does -z mean in Bash?

The expression -z string is true if the length of string is zero.

How to implement my very own URI scheme on Android

Complementing the @DanielLew answer, to get the values of the parameteres you have to do this:

URI example: myapp://path/to/what/i/want?keyOne=valueOne&keyTwo=valueTwo

in your activity:

Intent intent = getIntent();
if (Intent.ACTION_VIEW.equals(intent.getAction())) {
  Uri uri = intent.getData();
  String valueOne = uri.getQueryParameter("keyOne");
  String valueTwo = uri.getQueryParameter("keyTwo");
}

Passing Parameters JavaFX FXML

Here is an example for passing parameters to a fxml document through namespace.

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.BorderPane?>
<?import javafx.scene.layout.VBox?>
<VBox xmlns="http://javafx.com/javafx/null" xmlns:fx="http://javafx.com/fxml/1">
    <BorderPane>
        <center>
            <Label text="$labelText"/>
        </center>
    </BorderPane>
</VBox>

Define value External Text for namespace variable labelText:

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.io.IOException;

public class NamespaceParameterExampleApplication extends Application {

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

    @Override
    public void start(Stage primaryStage) throws IOException {
        final FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("namespace-parameter-example.fxml"));

        fxmlLoader.getNamespace()
                  .put("labelText", "External Text");

        final Parent root = fxmlLoader.load();

        primaryStage.setTitle("Namespace Parameter Example");
        primaryStage.setScene(new Scene(root, 400, 400));
        primaryStage.show();
    }
}

How to find and replace string?

Do we really need a Boost library for seemingly such a simple task?

To replace all occurences of a substring use this function:

std::string ReplaceString(std::string subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();
    }
    return subject;
}

If you need performance, here is an optimized function that modifies the input string, it does not create a copy of the string:

void ReplaceStringInPlace(std::string& subject, const std::string& search,
                          const std::string& replace) {
    size_t pos = 0;
    while ((pos = subject.find(search, pos)) != std::string::npos) {
         subject.replace(pos, search.length(), replace);
         pos += replace.length();
    }
}

Tests:

std::string input = "abc abc def";
std::cout << "Input string: " << input << std::endl;

std::cout << "ReplaceString() return value: " 
          << ReplaceString(input, "bc", "!!") << std::endl;
std::cout << "ReplaceString() input string not modified: " 
          << input << std::endl;

ReplaceStringInPlace(input, "bc", "??");
std::cout << "ReplaceStringInPlace() input string modified: " 
          << input << std::endl;

Output:

Input string: abc abc def
ReplaceString() return value: a!! a!! def
ReplaceString() input string not modified: abc abc def
ReplaceStringInPlace() input string modified: a?? a?? def

React : difference between <Route exact path="/" /> and <Route path="/" />

Take a look here: https://reacttraining.com/react-router/core/api/Route/exact-bool

exact: bool

When true, will only match if the path matches the location.pathname exactly.

**path**    **location.pathname**   **exact**   **matches?**

/one        /one/two                true        no
/one        /one/two                false       yes

SSL Error: CERT_UNTRUSTED while using npm command

I had same problem and finally I understood that my node version is old. For example, you can install the current active LTS node version in Ubuntu by the following steps:

sudo apt-get update
curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
sudo apt-get install nodejs -y

Installation instructions for more versions and systems can be found in the following link:

https://github.com/nodesource/distributions/blob/master/README.md

How to get query string parameter from MVC Razor markup?

Noneof the answers worked for me, I was getting "'HttpRequestBase' does not contain a definition for 'Query'", but this did work:

HttpContext.Current.Request.QueryString["index"]

Insertion sort vs Bubble Sort Algorithms

Another difference, I didn't see here:

Bubble sort has 3 value assignments per swap: you have to build a temporary variable first to save the value you want to push forward(no.1), than you have to write the other swap-variable into the spot you just saved the value of(no.2) and then you have to write your temporary variable in the spot other spot(no.3). You have to do that for each spot - you want to go forward - to sort your variable to the correct spot.

With insertion sort you put your variable to sort in a temporary variable and then put all variables in front of that spot 1 spot backwards, as long as you reach the correct spot for your variable. That makes 1 value assignement per spot. In the end you write your temp-variable into the the spot.

That makes far less value assignements, too.

This isn't the strongest speed-benefit, but i think it can be mentioned.

I hope, I expressed myself understandable, if not, sorry, I'm not a nativ Britain

What is an optional value in Swift?

From https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/OptionalChaining.html:

Optional chaining is a process for querying and calling properties, methods, and subscripts on an optional that might currently be nil. If the optional contains a value, the property, method, or subscript call succeeds; if the optional is nil, the property, method, or subscript call returns nil. Multiple queries can be chained together, and the entire chain fails gracefully if any link in the chain is nil.

To understand deeper, read the link above.

Undefined reference to sqrt (or other mathematical functions)

Just adding the #include <math.h> in c source file and -lm in Makefile at the end will work for me.

    gcc -pthread -o p3 p3.c -lm

Splitting a string at every n-th character

import java.util.ArrayList;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        for (String part : getParts("foobarspam", 3)) {
            System.out.println(part);
        }
    }
    private static List<String> getParts(String string, int partitionSize) {
        List<String> parts = new ArrayList<String>();
        int len = string.length();
        for (int i=0; i<len; i+=partitionSize)
        {
            parts.add(string.substring(i, Math.min(len, i + partitionSize)));
        }
        return parts;
    }
}

Excel: Creating a dropdown using a list in another sheet?

That cannot be done in excel 2007. The list must be in the same sheet as your data. It might work in later versions though.

How do write IF ELSE statement in a MySQL query

according to the mySQL reference manual this the syntax of using if and else statement :

IF search_condition THEN statement_list
[ELSEIF search_condition THEN statement_list] ...
[ELSE statement_list]
END IF

So regarding your query :

x = IF((action=2)&&(state=0),1,2);

or you can use

IF ((action=2)&&(state=0)) then 
state = 1;
ELSE 
state = 2;
END IF;

There is good example in this link : http://easysolutionweb.com/sql-pl-sql/how-to-use-if-and-else-in-mysql/

What exactly is LLVM?

According to 'Getting Started With LLVM Core Libraries' book (c):

In fact, the name LLVM might refer to any of the following:

  • The LLVM project/infrastructure: This is an umbrella for several projects that, together, form a complete compiler: frontends, backends, optimizers, assemblers, linkers, libc++, compiler-rt, and a JIT engine. The word "LLVM" has this meaning, for example, in the following sentence: "LLVM is comprised of several projects".

  • An LLVM-based compiler: This is a compiler built partially or completely with the LLVM infrastructure. For example, a compiler might use LLVM for the frontend and backend but use GCC and GNU system libraries to perform the final link. LLVM has this meaning in the following sentence, for example: "I used LLVM to compile C programs to a MIPS platform".

  • LLVM libraries: This is the reusable code portion of the LLVM infrastructure. For example, LLVM has this meaning in the sentence: "My project uses LLVM to generate code through its Just-in-Time compilation framework".

  • LLVM core: The optimizations that happen at the intermediate language level and the backend algorithms form the LLVM core where the project started. LLVM has this meaning in the following sentence: "LLVM and Clang are two different projects".

  • The LLVM IR: This is the LLVM compiler intermediate representation. LLVM has this meaning when used in sentences such as "I built a frontend that translates my own language to LLVM".

What does $@ mean in a shell script?

$@ is nearly the same as $*, both meaning "all command line arguments". They are often used to simply pass all arguments to another program (thus forming a wrapper around that other program).

The difference between the two syntaxes shows up when you have an argument with spaces in it (e.g.) and put $@ in double quotes:

wrappedProgram "$@"
# ^^^ this is correct and will hand over all arguments in the way
#     we received them, i. e. as several arguments, each of them
#     containing all the spaces and other uglinesses they have.
wrappedProgram "$*"
# ^^^ this will hand over exactly one argument, containing all
#     original arguments, separated by single spaces.
wrappedProgram $*
# ^^^ this will join all arguments by single spaces as well and
#     will then split the string as the shell does on the command
#     line, thus it will split an argument containing spaces into
#     several arguments.

Example: Calling

wrapper "one two    three" four five "six seven"

will result in:

"$@": wrappedProgram "one two    three" four five "six seven"
"$*": wrappedProgram "one two    three four five six seven"
                             ^^^^ These spaces are part of the first
                                  argument and are not changed.
$*:   wrappedProgram one two three four five six seven

How do I convert an ANSI encoded file to UTF-8 with Notepad++?

If you don't have non-ASCII characters (codepoints 128 and above) in your file, UTF-8 without BOM is the same as ASCII, byte for byte - so Notepad++ will guess wrong.

What you need to do is to specify the character encoding when serving the AJAX response - e.g. with PHP, you'd do this:

header('Content-Type: application/json; charset=utf-8');

The important part is to specify the charset with every JS response - else IE will fall back to user's system default encoding, which is wrong most of the time.

How do I add an "Add to Favorites" button or link on my website?

This code is the corrected version of iambriansreed's answer:

<script type="text/javascript">
    $(function() {
        $("#bookmarkme").click(function() {
            // Mozilla Firefox Bookmark
            if ('sidebar' in window && 'addPanel' in window.sidebar) { 
                window.sidebar.addPanel(location.href,document.title,"");
            } else if( /*@cc_on!@*/false) { // IE Favorite
                window.external.AddFavorite(location.href,document.title); 
            } else { // webkit - safari/chrome
                alert('Press ' + (navigator.userAgent.toLowerCase().indexOf('mac') != - 1 ? 'Command/Cmd' : 'CTRL') + ' + D to bookmark this page.');
            }
        });
    });
</script>

How do I crop an image in Java?

You need to read about Java Image API and mouse-related API, maybe somewhere under the java.awt.event package.

For a start, you need to be able to load and display the image to the screen, maybe you'll use a JPanel.

Then from there, you will try implement a mouse motion listener interface and other related interfaces. Maybe you'll get tied on the mouseDragged method...

For a mousedragged action, you will get the coordinate of the rectangle form by the drag...

Then from these coordinates, you will get the subimage from the image you have and you sort of redraw it anew....

And then display the cropped image... I don't know if this will work, just a product of my imagination... just a thought!

How should I escape commas and speech marks in CSV files so they work in Excel?

According to Yashu's instructions, I wrote the following function (it's PL/SQL code, but it should be easily adaptable to any other language).

FUNCTION field(str IN VARCHAR2) RETURN VARCHAR2 IS
    C_NEWLINE CONSTANT CHAR(1) := '
'; -- newline is intentional

    v_aux VARCHAR2(32000);
    v_has_double_quotes BOOLEAN;
    v_has_comma BOOLEAN;
    v_has_newline BOOLEAN;
BEGIN
    v_has_double_quotes := instr(str, '"') > 0;
    v_has_comma := instr(str,',') > 0;
    v_has_newline := instr(str, C_NEWLINE) > 0;

    IF v_has_double_quotes OR v_has_comma OR v_has_newline THEN
        IF v_has_double_quotes THEN
            v_aux := replace(str,'"','""');
        ELSE
            v_aux := str;
        END IF;
        return '"'||v_aux||'"';
    ELSE
        return str;
    END IF;
END;

Vertical line using XML drawable

add this in your styles.xml

        <style name="Divider">
            <item name="android:layout_width">1dip</item>
            <item name="android:layout_height">match_parent</item>
            <item name="android:background">@color/divider_color</item>
        </style>

        <style name="Divider_invisible">
            <item name="android:layout_width">1dip</item>
            <item name="android:layout_height">match_parent</item>
        </style>

then wrap this style in a linear layout where you want the vertical line, I used the vertical line as a column divider in my table. 

     <TableLayout
                android:id="@+id/table"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal"
                android:stretchColumns="*" >

                <TableRow
                    android:id="@+id/tableRow1"
                    android:layout_width="fill_parent"
                    android:layout_height="match_parent"
                    android:background="#92C94A" >

                    <TextView
                        android:id="@+id/textView11"
                        android:paddingBottom="10dp"
                        android:paddingLeft="5dp"
                        android:paddingRight="5dp"
                        android:paddingTop="10dp" />
    //...................................................................    

                    <LinearLayout
                        android:layout_width="1dp"
                        android:layout_height="match_parent" >

                        <View style="@style/Divider_invisible" />
                    </LinearLayout>
        //...................................................................
                    <TextView
                        android:id="@+id/textView12"
                        android:paddingBottom="10dp"
                        android:paddingLeft="5dp"
                        android:paddingRight="5dp"
                        android:paddingTop="10dp"
                        android:text="@string/main_wo_colon"
                        android:textColor="@color/white"
                        android:textSize="16sp" />
  //...............................................................  
                    <LinearLayout
                        android:layout_width="1dp"
                        android:layout_height="match_parent" >

                        <View style="@style/Divider" />
                    </LinearLayout>

    //...................................................................
                    <TextView
                        android:id="@+id/textView13"
                        android:paddingBottom="10dp"
                        android:paddingLeft="5dp"
                        android:paddingRight="5dp"
                        android:paddingTop="10dp"
                        android:text="@string/side_wo_colon"
                        android:textColor="@color/white"
                        android:textSize="16sp" />

                    <LinearLayout
                        android:layout_width="1dp"
                        android:layout_height="match_parent" >

                        <View style="@style/Divider" />
                    </LinearLayout>

                    <TextView
                        android:id="@+id/textView14"
                        android:paddingBottom="10dp"
                        android:paddingLeft="5dp"
                        android:paddingRight="5dp"
                        android:paddingTop="10dp"
                        android:text="@string/total"
                        android:textColor="@color/white"
                        android:textSize="16sp" />
                </TableRow>

                <!-- display this button in 3rd column via layout_column(zero based) -->

                <TableRow
                    android:id="@+id/tableRow2"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:background="#6F9C33" >

                    <TextView
                        android:id="@+id/textView21"
                        android:padding="5dp"
                        android:text="@string/servings"
                        android:textColor="@color/white"
                        android:textSize="16sp" />

                    <LinearLayout
                        android:layout_width="1dp"
                        android:layout_height="match_parent" >

                        <View style="@style/Divider" />
                    </LinearLayout>

    ..........
    .......
    ......

Drop default constraint on a column in TSQL

I would like to refer a previous question, Because I have faced same problem and solved by this solution. First of all a constraint is always built with a Hash value in it's name. So problem is this HASH is varies in different Machine or Database. For example DF__Companies__IsGlo__6AB17FE4 here 6AB17FE4 is the hash value(8 bit). So I am referring a single script which will be fruitful to all

DECLARE @Command NVARCHAR(MAX)
     declare @table_name nvarchar(256)
     declare @col_name nvarchar(256)
     set @table_name = N'ProcedureAlerts'
     set @col_name = N'EmailSent'

     select @Command ='Alter Table dbo.ProcedureAlerts Drop Constraint [' + ( select d.name
     from 
         sys.tables t
         join sys.default_constraints d on d.parent_object_id = t.object_id
         join sys.columns c on c.object_id = t.object_id
                               and c.column_id = d.parent_column_id
     where 
         t.name = @table_name
         and c.name = @col_name) + ']'

    --print @Command
    exec sp_executesql @Command

It will drop your default constraint. However if you want to create it again you can simply try this

ALTER TABLE [dbo].[ProcedureAlerts] ADD DEFAULT((0)) FOR [EmailSent]

Finally, just simply run a DROP command to drop the column.

Convert line endings

Doing this with POSIX is tricky:

  • POSIX Sed does not support \r or \15. Even if it did, the in place option -i is not POSIX

  • POSIX Awk does support \r and \15, however the -i inplace option is not POSIX

  • d2u and dos2unix are not POSIX utilities, but ex is

  • POSIX ex does not support \r, \15, \n or \12

To remove carriage returns:

awk 'BEGIN{RS="^$";ORS="";getline;gsub("\r","");print>ARGV[1]}' file

To add carriage returns:

awk 'BEGIN{RS="^$";ORS="";getline;gsub("\n","\r&");print>ARGV[1]}' file

How to get week number of the month from the date in sql server 2008

Here are 2 different ways, both are assuming the week starts on monday

If you want weeks to be whole, so they belong to the month in which they start: So saturday 2012-09-01 and sunday 2012-09-02 is week 4 and monday 2012-09-03 is week 1 use this:

declare @date datetime = '2012-09-01'
select datepart(day, datediff(day, 0, @date)/7 * 7)/7 + 1

If your weeks cut on monthchange so saturday 2012-09-01 and sunday 2012-09-02 is week 1 and monday 2012-09-03 is week 2 use this:

declare @date datetime = '2012-09-01'
select datediff(week, dateadd(week, 
  datediff(day,0,dateadd(month,
    datediff(month,0,@date),0))/7, 0),@date-1) + 1

I recieved an email from Gerald. He pointed out a flaw in the second method. This should be fixed now

How do I look inside a Python object?

Many good tipps already, but the shortest and easiest (not necessarily the best) has yet to be mentioned:

object?

How to insert text into the textarea at the current cursor position?

Changed it to getElementById(myField)

 function insertAtCursor(myField, myValue) {
    //IE support
    if (document.selection) {
        document.getElementById(myField).focus();
        sel = document.selection.createRange();
        sel.text = myValue;
    }
    //MOZILLA and others
    else if (document.getElementById(myField).selectionStart || document.getElementById(myField).selectionStart == '0') {
        var startPos = document.getElementById(myField).selectionStart;
        var endPos = document.getElementById(myField).selectionEnd;
        document.getElementById(myField).value = document.getElementById(myField).value.substring(0, startPos)
            + myValue
            + document.getElementById(myField).value.substring(endPos, document.getElementById(myField).value.length);
    } else {
        document.getElementById(myField).value += myValue;
    }
}

How to properly create composite primary keys - MYSQL

the syntax is CONSTRAINT constraint_name PRIMARY KEY(col1,col2,col3) for example ::

CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)

the above example will work if you are writting it while you are creating the table for example ::

CREATE TABLE person (
   P_Id int ,
   ............,
   ............,
   CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)
);

to add this constraint to an existing table you need to follow the following syntax

ALTER TABLE table_name ADD CONSTRAINT constraint_name PRIMARY KEY (P_Id,LastName)

Select a Dictionary<T1, T2> with LINQ

A more explicit option is to project collection to an IEnumerable of KeyValuePair and then convert it to a Dictionary.

Dictionary<int, string> dictionary = objects
    .Select(x=> new KeyValuePair<int, string>(x.Id, x.Name))
    .ToDictionary(x=>x.Key, x=>x.Value);

Bootstrap how to get text to vertical align in a div container

h2.text-left{
  position:relative;
  top:50%;
  transform: translateY(-50%);
  -webkit-transform: translateY(-50%);
  -ms-transform: translateY(-50%);
}

Explanation:

The top:50% style essentially pushes the header element down 50% from the top of the parent element. The translateY stylings also act in a similar manner by moving then element down 50% from the top.

Please note that this works well for headers with 1 (maybe 2) lines of text as this simply moves the top of the header element down 50% and then the rest of the content fills in below that, which means that with multiple lines of text it would appear to be slightly below vertically aligned.

A possible fix for multiple lines would be to use a percentage slightly less than 50%.

ERROR 1064 (42000): You have an error in your SQL syntax;

Use varchar instead of VAR_CHAR and omit the comma in the last line i.e.phone INT NOT NULL );. The last line during creating table is kept "comma free". Ex:- CREATE TABLE COMPUTER ( Model varchar(50) ); Here, since we have only one column ,that's why there is no comma used during entire code.

Why doesn't Dijkstra's algorithm work for negative weight edges?

Recall that in Dijkstra's algorithm, once a vertex is marked as "closed" (and out of the open set) - the algorithm found the shortest path to it, and will never have to develop this node again - it assumes the path developed to this path is the shortest.

But with negative weights - it might not be true. For example:

       A
      / \
     /   \
    /     \
   5       2
  /         \
  B--(-10)-->C

V={A,B,C} ; E = {(A,C,2), (A,B,5), (B,C,-10)}

Dijkstra from A will first develop C, and will later fail to find A->B->C


EDIT a bit deeper explanation:

Note that this is important, because in each relaxation step, the algorithm assumes the "cost" to the "closed" nodes is indeed minimal, and thus the node that will next be selected is also minimal.

The idea of it is: If we have a vertex in open such that its cost is minimal - by adding any positive number to any vertex - the minimality will never change.
Without the constraint on positive numbers - the above assumption is not true.

Since we do "know" each vertex which was "closed" is minimal - we can safely do the relaxation step - without "looking back". If we do need to "look back" - Bellman-Ford offers a recursive-like (DP) solution of doing so.

"Unorderable types: int() < str()"

The issue here is that input() returns a string in Python 3.x, so when you do your comparison, you are comparing a string and an integer, which isn't well defined (what if the string is a word, how does one compare a string and a number?) - in this case Python doesn't guess, it throws an error.

To fix this, simply call int() to convert your string to an integer:

int(input(...))

As a note, if you want to deal with decimal numbers, you will want to use one of float() or decimal.Decimal() (depending on your accuracy and speed needs).

Note that the more pythonic way of looping over a series of numbers (as opposed to a while loop and counting) is to use range(). For example:

def main():
    print("Let me Retire Financial Calculator")
    deposit = float(input("Please input annual deposit in dollars: $"))
    rate = int(input ("Please input annual rate in percentage: %")) / 100
    time = int(input("How many years until retirement?"))
    value = 0
    for x in range(1, time+1):
        value = (value * rate) + deposit
        print("The value of your account after" + str(x) + "years will be $" + str(value))

How to increase executionTimeout for a long-running query?

You can set executionTimeout in web.config to support the longer execution time.

executionTimeout specifies the maximum number of seconds that a request is allowed to execute before being automatically shut down by ASP.NET. MSDN

<httpRuntime  executionTimeout = "300" />

This make execution timeout to five minutes.

Optional Int32 attribute.

Specifies the maximum number of seconds that a request is allowed to execute before being automatically shut down by ASP.NET.

This time-out applies only if the debug attribute in the compilation element is False. Therefore, if the debug attribute is True, you do not have to set this attribute to a large value in order to avoid application shutdown while you are debugging. The default is 110 seconds, Reference.

Linux Script to check if process is running and act on the result

If you changed awk '{print $1}' to '{ $1=""; print $0}' you will get all processes except for the first as a result. It will start with the field separator (a space generally) but I don't recall killall caring. So:

#! /bin/bash

logfile="/var/oscamlog/oscam1check.log"

case "$(pidof oscam1 | wc -w)" in

0)  echo "oscam1 not running, restarting oscam1:     $(date)" >> $logfile
    /usr/local/bin/oscam1 -b -c /usr/local/etc/oscam1 -t /usr/local/tmp.oscam1 &
    ;;
2)  echo "oscam1 running, all OK:     $(date)" >> $logfile
    ;;
*)  echo "multiple instances of oscam1 running. Stopping & restarting oscam1:     $(date)" >> $logfile
    kill $(pidof oscam1 | awk '{ $1=""; print $0}')
    ;;
esac

It is worth noting that the pidof route seems to work fine for commands that have no spaces, but you would probably want to go back to a ps-based string if you were looking for, say, a python script named myscript that showed up under ps like

root 22415 54.0 0.4 89116 79076 pts/1 S 16:40 0:00 /usr/bin/python /usr/bin/myscript

Just an FYI

Cannot find Dumpbin.exe

A little refresh as for the Visual Studio 2015.

DUMPBIN is being shipped within Common Tools for Visual C++, so be sure to select this feature in the process of installation of Visual Studio. The utility resides at:

C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\

It become available within Developer Command Prompt for VS 2015, which can be executed from Start Menu:

Visual Studio 2015 \ Visual Studio Tools \ Developer Command Prompt for VS2015

If you want to make it available in the regular command prompt, then add the utility's location to the PATH environment variable on your machine.

enter image description here

How to get a specific column value from a DataTable in c#

The table normally contains multiple rows. Use a loop and use row.Field<string>(0) to access the value of each row.

foreach(DataRow row in dt.Rows)
{
    string file = row.Field<string>("File");
}

You can also access it via index:

foreach(DataRow row in dt.Rows)
{
    string file = row.Field<string>(0);
}

If you expect only one row, you can also use the indexer of DataRowCollection:

string file = dt.Rows[0].Field<string>(0); 

Since this fails if the table is empty, use dt.Rows.Count to check if there is a row:

if(dt.Rows.Count > 0)
    file = dt.Rows[0].Field<string>(0);

Change default icon

If your designated icon shows when you run the EXE but not when you run it from Visual Studio, then, for a WPF project add the following at the top of your XAML: Icon="Images\MyIcon.ico". Put this just where you have the Title, and xmlns definitions. (Assuming you have an Images folder in your project, and that you added MyIcon.ico there).

ASP.NET Core Web API Authentication

To use this only for specific controllers for example use this:

app.UseWhen(x => (x.Request.Path.StartsWithSegments("/api", StringComparison.OrdinalIgnoreCase)), 
            builder =>
            {
                builder.UseMiddleware<AuthenticationMiddleware>();
            });

SQL Server: Null VS Empty String

The conceptual differences between NULL and "empty-string" are real and very important in database design, but often misunderstood and improperly applied - here's a short description of the two:

NULL - means that we do NOT know what the value is, it may exist, but it may not exist, we just don't know.

Empty-String - means we know what the value is and that it is nothing.

Here's a simple example: Suppose you have a table with people's names including separate columns for first_name, middle_name, and last_name. In the scenario where first_name = 'John', last_name = 'Doe', and middle_name IS NULL, it means that we do not know what the middle name is, or if it even exists. Change that scenario such that middle_name = '' (i.e. empty-string), and it now means that we know that there is no middle name.

I once heard a SQL Server instructor promote making every character type column in a database required, and then assigning a DEFAULT VALUE to each of either '' (empty-string), or 'unknown'. In stating this, the instructor demonstrated he did not have a clear understanding of the difference between NULLs and empty-strings. Admittedly, the differences can seem confusing, but for me the above example helps to clarify the difference. Also, it is important to understand the difference when writing SQL code, and properly handle for NULLs as well as empty-strings.

"Call to undefined function mysql_connect()" after upgrade to php-7

From the PHP Manual:

Warning This extension was deprecated in PHP 5.5.0, and it was removed in PHP 7.0.0. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide. Alternatives to this function include:

mysqli_connect()

PDO::__construct()

use MySQLi or PDO

<?php
$con = mysqli_connect('localhost', 'username', 'password', 'database');

What's the difference between lists and tuples?

This is an example of Python lists:

my_list = [0,1,2,3,4]
top_rock_list = ["Bohemian Rhapsody","Kashmir","Sweet Emotion", "Fortunate Son"]

This is an example of Python tuple:

my_tuple = (a,b,c,d,e)
celebrity_tuple = ("John", "Wayne", 90210, "Actor", "Male", "Dead")

Python lists and tuples are similar in that they both are ordered collections of values. Besides the shallow difference that lists are created using brackets "[ ... , ... ]" and tuples using parentheses "( ... , ... )", the core technical "hard coded in Python syntax" difference between them is that the elements of a particular tuple are immutable whereas lists are mutable (...so only tuples are hashable and can be used as dictionary/hash keys!). This gives rise to differences in how they can or can't be used (enforced a priori by syntax) and differences in how people choose to use them (encouraged as 'best practices,' a posteriori, this is what smart programers do). The main difference a posteriori in differentiating when tuples are used versus when lists are used lies in what meaning people give to the order of elements.

For tuples, 'order' signifies nothing more than just a specific 'structure' for holding information. What values are found in the first field can easily be switched into the second field as each provides values across two different dimensions or scales. They provide answers to different types of questions and are typically of the form: for a given object/subject, what are its attributes? The object/subject stays constant, the attributes differ.

For lists, 'order' signifies a sequence or a directionality. The second element MUST come after the first element because it's positioned in the 2nd place based on a particular and common scale or dimension. The elements are taken as a whole and mostly provide answers to a single question typically of the form, for a given attribute, how do these objects/subjects compare? The attribute stays constant, the object/subject differs.

There are countless examples of people in popular culture and programmers who don't conform to these differences and there are countless people who might use a salad fork for their main course. At the end of the day, it's fine and both can usually get the job done.

To summarize some of the finer details

Similarities:

  1. Duplicates - Both tuples and lists allow for duplicates
  2. Indexing, Selecting, & Slicing - Both tuples and lists index using integer values found within brackets. So, if you want the first 3 values of a given list or tuple, the syntax would be the same:

    >>> my_list[0:3]
    [0,1,2]
    >>> my_tuple[0:3]
    [a,b,c]
    
  3. Comparing & Sorting - Two tuples or two lists are both compared by their first element, and if there is a tie, then by the second element, and so on. No further attention is paid to subsequent elements after earlier elements show a difference.

    >>> [0,2,0,0,0,0]>[0,0,0,0,0,500]
    True
    >>> (0,2,0,0,0,0)>(0,0,0,0,0,500)
    True
    

Differences: - A priori, by definition

  1. Syntax - Lists use [], tuples use ()

  2. Mutability - Elements in a given list are mutable, elements in a given tuple are NOT mutable.

    # Lists are mutable:
    >>> top_rock_list
    ['Bohemian Rhapsody', 'Kashmir', 'Sweet Emotion', 'Fortunate Son']
    >>> top_rock_list[1]
    'Kashmir'
    >>> top_rock_list[1] = "Stairway to Heaven"
    >>> top_rock_list
    ['Bohemian Rhapsody', 'Stairway to Heaven', 'Sweet Emotion', 'Fortunate Son']
    
    # Tuples are NOT mutable:       
    >>> celebrity_tuple
    ('John', 'Wayne', 90210, 'Actor', 'Male', 'Dead')
    >>> celebrity_tuple[5]
    'Dead'
    >>> celebrity_tuple[5]="Alive"
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    TypeError: 'tuple' object does not support item assignment
    
  3. Hashtables (Dictionaries) - As hashtables (dictionaries) require that its keys are hashable and therefore immutable, only tuples can act as dictionary keys, not lists.

    #Lists CAN'T act as keys for hashtables(dictionaries)
    >>> my_dict = {[a,b,c]:"some value"}
    Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    TypeError: unhashable type: 'list'
    
    #Tuples CAN act as keys for hashtables(dictionaries)
    >>> my_dict = {("John","Wayne"): 90210}
    >>> my_dict
    {('John', 'Wayne'): 90210}
    

Differences - A posteriori, in usage

  1. Homo vs. Heterogeneity of Elements - Generally list objects are homogenous and tuple objects are heterogeneous. That is, lists are used for objects/subjects of the same type (like all presidential candidates, or all songs, or all runners) whereas although it's not forced by), whereas tuples are more for heterogenous objects.

  2. Looping vs. Structures - Although both allow for looping (for x in my_list...), it only really makes sense to do it for a list. Tuples are more appropriate for structuring and presenting information (%s %s residing in %s is an %s and presently %s % ("John","Wayne",90210, "Actor","Dead"))

Execute Insert command and return inserted Id in Sql

SQL Server stored procedure:

CREATE PROCEDURE [dbo].[INS_MEM_BASIC]
    @na varchar(50),
    @occ varchar(50),
    @New_MEM_BASIC_ID int OUTPUT
AS
BEGIN
    SET NOCOUNT ON;

    INSERT INTO Mem_Basic
    VALUES (@na, @occ)

    SELECT @New_MEM_BASIC_ID = SCOPE_IDENTITY()
END

C# code:

public int CreateNewMember(string Mem_NA, string Mem_Occ )
{
    // values 0 --> -99 are SQL reserved.
    int new_MEM_BASIC_ID = -1971;   
    SqlConnection SQLconn = new SqlConnection(Config.ConnectionString);
    SqlCommand cmd = new SqlCommand("INS_MEM_BASIC", SQLconn);

    cmd.CommandType = CommandType.StoredProcedure;

    SqlParameter outPutVal = new SqlParameter("@New_MEM_BASIC_ID", SqlDbType.Int);

    outPutVal.Direction = ParameterDirection.Output;
    cmd.Parameters.Add(outPutVal);
    cmd.Parameters.Add("@na", SqlDbType.Int).Value = Mem_NA;
    cmd.Parameters.Add("@occ", SqlDbType.Int).Value = Mem_Occ;

    SQLconn.Open();
    cmd.ExecuteNonQuery();
    SQLconn.Close();

    if (outPutVal.Value != DBNull.Value) new_MEM_BASIC_ID = Convert.ToInt32(outPutVal.Value);
        return new_MEM_BASIC_ID;
}

I hope these will help to you ....

You can also use this if you want ...

public int CreateNewMember(string Mem_NA, string Mem_Occ )
{
    using (SqlConnection con=new SqlConnection(Config.ConnectionString))
    {
        int newID;
        var cmd = "INSERT INTO Mem_Basic(Mem_Na,Mem_Occ) VALUES(@na,@occ);SELECT CAST(scope_identity() AS int)";

        using(SqlCommand cmd=new SqlCommand(cmd, con))
        {
            cmd.Parameters.AddWithValue("@na", Mem_NA);
            cmd.Parameters.AddWithValue("@occ", Mem_Occ);

            con.Open();
            newID = (int)insertCommand.ExecuteScalar();

            if (con.State == System.Data.ConnectionState.Open) con.Close();
                return newID;
        }
    }
}

How to get rid of the "No bootable medium found!" error in Virtual Box?

Follow the steps below:

1) Select your VM Instance. Go to Settings->Storage

2) Under the storage tree select the default image or "Empty"(which ever is present)

3) Under the attributes frame, click on the CD image and select "Choose a virtual CD/DVD disk file"

4) Browse and select the image file(iso or what ever format) from the system

5) Select OK.

Abishek's solution is correct. But the highlighted area in 2nd image could be misleading.

How to write UPDATE SQL with Table alias in SQL Server 2008?

The syntax for using an alias in an update statement on SQL Server is as follows:

UPDATE Q
SET Q.TITLE = 'TEST'
FROM HOLD_TABLE Q
WHERE Q.ID = 101;

The alias should not be necessary here though.

How add "or" in switch statements?

You do it by stacking case labels:

switch(myvar)
{
    case 2:
    case 5:
    ...
    break;

    case 7: 
    case 12:
    ...
    break;
    ...
}

Rails: call another controller action from a controller

Composition to the rescue!

Given the reason, rather than invoking actions across controllers one should design controllers to seperate shared and custom parts of the code. This will help to avoid both - code duplication and breaking MVC pattern.

Although that can be done in a number of ways, using concerns (composition) is a good practice.

# controllers/a_controller.rb
class AController < ApplicationController
  include Createable

  private def redirect_url
    'one/url'
  end
end

# controllers/b_controller.rb
class BController < ApplicationController
  include Createable

  private def redirect_url
    'another/url'
  end
end

# controllers/concerns/createable.rb
module Createable
  def create
    do_usefull_things
    redirect_to redirect_url
  end
end

Hope that helps.

How to adjust the size of y axis labels only in R?

Don't know what you are doing (helpful to show what you tried that didn't work), but your claim that cex.axis only affects the x-axis is not true:

set.seed(123)
foo <- data.frame(X = rnorm(10), Y = rnorm(10))
plot(Y ~ X, data = foo, cex.axis = 3)

at least for me with:

> sessionInfo()
R version 2.11.1 Patched (2010-08-17 r52767)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_GB.UTF-8        LC_COLLATE=en_GB.UTF-8    
 [5] LC_MONETARY=C              LC_MESSAGES=en_GB.UTF-8   
 [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] ggplot2_0.8.8 proto_0.3-8   reshape_0.8.3 plyr_1.2.1   

loaded via a namespace (and not attached):
[1] digest_0.4.2 tools_2.11.1

Also, cex.axis affects the labelling of tick marks. cex.lab is used to control what R call the axis labels.

plot(Y ~ X, data = foo, cex.lab = 3)

but even that works for both the x- and y-axis.


Following up Jens' comment about using barplot(). Check out the cex.names argument to barplot(), which allows you to control the bar labels:

dat <- rpois(10, 3) names(dat) <- LETTERS[1:10] barplot(dat, cex.names = 3, cex.axis = 2)

As you mention that cex.axis was only affecting the x-axis I presume you had horiz = TRUE in your barplot() call as well? As the bar labels are not drawn with an axis() call, applying Joris' (otherwise very useful) answer with individual axis() calls won't help in this situation with you using barplot()

HTH

How to add an image in Tkinter?

There is no "Syntax Error" in the code above - it either ocurred in some other line (the above is not all of your code, as there are no imports, neither the declaration of your path variable) or you got some other error type.

The example above worked fine for me, testing on the interactive interpreter.

Check that an email address is valid on iOS

To check if a string variable contains a valid email address, the easiest way is to test it against a regular expression. There is a good discussion of various regex's and their trade-offs at regular-expressions.info.

Here is a relatively simple one that leans on the side of allowing some invalid addresses through: ^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,6}$

How you can use regular expressions depends on the version of iOS you are using.

iOS 4.x and Later

You can use NSRegularExpression, which allows you to compile and test against a regular expression directly.

iOS 3.x

Does not include the NSRegularExpression class, but does include NSPredicate, which can match against regular expressions.

NSString *emailRegex = ...;
NSPredicate *emailTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", emailRegex];
BOOL isValid = [emailTest evaluateWithObject:checkString];

Read a full article about this approach at cocoawithlove.com.

iOS 2.x

Does not include any regular expression matching in the Cocoa libraries. However, you can easily include RegexKit Lite in your project, which gives you access to the C-level regex APIs included on iOS 2.0.

How to remove all options from a dropdown using jQuery / JavaScript

You didn't say on which event.Just use below on your event listener.Or in your page load

$('#models').empty()

Then to repopulate

$.getJSON('@Url.Action("YourAction","YourController")',function(data){
 var dropdown=$('#models');
dropdown.empty();  
$.each(data, function (index, item) {
    dropdown.append(
        $('<option>', {
            value: item.valueField,
            text: item.DisplayField
        }, '</option>'))
      }
     )});

Rewrite URL after redirecting 404 error htaccess

Try adding this rule to the top of your htaccess:

RewriteEngine On
RewriteRule ^404/?$ /pages/errors/404.php [L]

Then under that (or any other rules that you have):

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^ http://domain.com/404/ [L,R]

What is difference between INNER join and OUTER join

Inner join - An inner join using either of the equivalent queries gives the intersection of the two tables, i.e. the two rows they have in common.
Left outer join - A left outer join will give all rows in A, plus any common rows in B.
Full outer join - A full outer join will give you the union of A and B, i.e. All the rows in A and all the rows in B. If something in A doesn't have a corresponding datum in B, then the B portion is null, and vice versa. check this

How to install Intellij IDEA on Ubuntu?

JetBrains has a new application called the Toolbox App which quickly and easily installs any JetBrains software you want, assuming you have the license. It also manages your login once to apply across all JetBrains software, a very useful feature.

To use it, download the tar.gz file here, then extract it and run the included executable jetbrains-toolbox. Then sign in, and press install next to IntelliJ IDEA:

enter image description here

If you want to move the executable to /usr/bin/ feel free, however it works fine out of the box wherever you extract it to.

This will also make the appropriate desktop entries upon install.

Replacing NULL and empty string within Select statement

Sounds like you want a view instead of altering actual table data.

Coalesce(NullIf(rtrim(Address.Country),''),'United States')

This will force your column to be null if it is actually an empty string (or blank string) and then the coalesce will have a null to work with.

Multi-line string with extra space (preserved indentation)

If you're trying to get the string into a variable, another easy way is something like this:

USAGE=$(cat <<-END
    This is line one.
    This is line two.
    This is line three.
END
)

If you indent your string with tabs (i.e., '\t'), the indentation will be stripped out. If you indent with spaces, the indentation will be left in.

NOTE: It is significant that the last closing parenthesis is on another line. The END text must appear on a line by itself.

Order columns through Bootstrap4

Since column-ordering doesn't work in Bootstrap 4 beta as described in the code provided in the revisited answer above, you would need to use the following (as indicated in the codeply 4 Flexbox order demo - alpha/beta links that were provided in the answer).

<div class="container">
<div class="row">
    <div class="col-3 col-md-6">
        <div class="card card-block">1</div>
    </div>
    <div class="col-6 col-md-12  flex-md-last">
        <div class="card card-block">3</div>
    </div>
    <div class="col-3 col-md-6 ">
        <div class="card card-block">2</div>
    </div>
</div>

Note however that the "Flexbox order demo - beta" goes to an alpha codebase, and changing the codebase to Beta (and running it) results in the divs incorrectly displaying in a single column -- but that looks like a codeply issue since cutting and pasting the code out of codeply works as described.

How to get old Value with onchange() event in text box

You should use HTML5 data attributes. You can create your own attributes and save different values in them.

Codesign error: Provisioning profile cannot be found after deleting expired profile

Select the lines in codesigning that are blank under Any iOS SDK and select the right certificate.

How to run a maven created jar file using just the command line

Just use the exec-maven-plugin.

<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.2.1</version>
            <configuration>
                <mainClass>com.example.Main</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

Then you run you program:

mvn exec:java

Detach (move) subdirectory into separate Git repository

Update: This process is so common, that the git team made it much simpler with a new tool, git subtree. See here: Detach (move) subdirectory into separate Git repository


You want to clone your repository and then use git filter-branch to mark everything but the subdirectory you want in your new repo to be garbage-collected.

  1. To clone your local repository:

    git clone /XYZ /ABC
    

    (Note: the repository will be cloned using hard-links, but that is not a problem since the hard-linked files will not be modified in themselves - new ones will be created.)

  2. Now, let us preserve the interesting branches which we want to rewrite as well, and then remove the origin to avoid pushing there and to make sure that old commits will not be referenced by the origin:

    cd /ABC
    for i in branch1 br2 br3; do git branch -t $i origin/$i; done
    git remote rm origin
    

    or for all remote branches:

    cd /ABC
    for i in $(git branch -r | sed "s/.*origin\///"); do git branch -t $i origin/$i; done
    git remote rm origin
    
  3. Now you might want to also remove tags which have no relation with the subproject; you can also do that later, but you might need to prune your repo again. I did not do so and got a WARNING: Ref 'refs/tags/v0.1' is unchanged for all tags (since they were all unrelated to the subproject); additionally, after removing such tags more space will be reclaimed. Apparently git filter-branch should be able to rewrite other tags, but I could not verify this. If you want to remove all tags, use git tag -l | xargs git tag -d.

  4. Then use filter-branch and reset to exclude the other files, so they can be pruned. Let's also add --tag-name-filter cat --prune-empty to remove empty commits and to rewrite tags (note that this will have to strip their signature):

    git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter ABC -- --all
    

    or alternatively, to only rewrite the HEAD branch and ignore tags and other branches:

    git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter ABC HEAD
    
  5. Then delete the backup reflogs so the space can be truly reclaimed (although now the operation is destructive)

    git reset --hard
    git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d
    git reflog expire --expire=now --all
    git gc --aggressive --prune=now
    

    and now you have a local git repository of the ABC sub-directory with all its history preserved.

Note: For most uses, git filter-branch should indeed have the added parameter -- --all. Yes that's really --space-- all. This needs to be the last parameters for the command. As Matli discovered, this keeps the project branches and tags included in the new repo.

Edit: various suggestions from comments below were incorporated to make sure, for instance, that the repository is actually shrunk (which was not always the case before).

Java Keytool error after importing certificate , "keytool error: java.io.FileNotFoundException & Access Denied"

I even run the command prompt as Administrator but it didn't work for me with the below error.

'keytool' is not recognized as an internal or external command,
 operable program or batch file.

If the path to the keytool is not in your System paths then you will need to use the full path to use the keytool, which is

C:\Program Files\Java\jre<version>\bin

So, the command should be like

"C:\Program Files\Java\jre<version>\bin\keytool.exe" -importcert -alias certificateFileAlias -file CertificateFileName.cer -keystore cacerts

that worked for me.

How to Set/Update State of StatefulWidget from other StatefulWidget in Flutter?

I would like to extend Mohamed Elrashid answer, in case you require to pass a variable from the child widget to the parent widget

On child widget:

class ChildWidget extends StatefulWidget {
  final Function() notifyParent;
  ChildWidget({Key key, @required this.notifyParent}) : super(key: key);
}

On parent widget

void refresh(dynamic childValue) {
  setState(() {
    _parentVariable = childValue;
  });
}

On parent widget: pass the function above to the child widget

new ChildWidget( notifyParent: refresh ); 

On child widget: call the parent function with any variable from the the child widget

widget.notifyParent(childVariable);

Equivalent of .bat in mac os

The common convention would be to put it in a .sh file that looks like this -

#!/bin/bash
java -cp  ".;./supportlibraries/Framework_Core.jar;... etc

Note that '\' become '/'.

You could execute as

sh myfile.sh

or set the x bit on the file

chmod +x myfile.sh

and then just call

myfile.sh

xampp MySQL does not start

I found out that re-installing Xampp as an administrator and running it as an Administrator worked.

Serialize form data to JSON

Here's a function for this use case:

function getFormData($form){
    var unindexed_array = $form.serializeArray();
    var indexed_array = {};

    $.map(unindexed_array, function(n, i){
        indexed_array[n['name']] = n['value'];
    });

    return indexed_array;
}

Usage:

var $form = $("#form_data");
var data = getFormData($form);

Is it possible to remove inline styles with jQuery?

Change the plugin to no longer apply the style. That would be much better than removing the style there-after.

'printf' with leading zeros in C

Your format specifier is incorrect. From the printf() man page on my machine:

0 A zero '0' character indicating that zero-padding should be used rather than blank-padding. A '-' overrides a '0' if both are used;

Field Width: An optional digit string specifying a field width; if the output string has fewer characters than the field width it will be blank-padded on the left (or right, if the left-adjustment indicator has been given) to make up the field width (note that a leading zero is a flag, but an embedded zero is part of a field width);

Precision: An optional period, '.', followed by an optional digit string giving a precision which specifies the number of digits to appear after the decimal point, for e and f formats, or the maximum number of characters to be printed from a string; if the digit string is missing, the precision is treated as zero;

For your case, your format would be %09.3f:

#include <stdio.h>

int main(int argc, char **argv)
{
  printf("%09.3f\n", 4917.24);
  return 0;
}

Output:

$ make testapp
cc     testapp.c   -o testapp
$ ./testapp 
04917.240

Note that this answer is conditional on your embedded system having a printf() implementation that is standard-compliant for these details - many embedded environments do not have such an implementation.

Is there a C++ decompiler?

You can use IDA Pro by Hex-Rays. You will usually not get good C++ out of a binary unless you compiled in debugging information. Prepare to spend a lot of manual labor reversing the code.

If you didn't strip the binaries there is some hope as IDA Pro can produce C-alike code for you to work with. Usually it is very rough though, at least when I used it a couple of years ago.

How to execute IN() SQL queries with Spring's JDBCTemplate effectively?

Many things changed since 2009, but I can only find answers saying you need to use NamedParametersJDBCTemplate.

For me it works if I just do a

db.query(sql, new MyRowMapper(), StringUtils.join(listeParamsForInClause, ","));

using SimpleJDBCTemplate or JDBCTemplate

How does database indexing work?

Classic example "Index in Books"

Consider a "Book" of 1000 pages, divided by 10 Chapters, each section with 100 pages.

Simple, huh?

Now, imagine you want to find a particular Chapter that contains a word "Alchemist". Without an index page, you have no other option than scanning through the entire book/Chapters. i.e: 1000 pages.

This analogy is known as "Full Table Scan" in database world.

enter image description here

But with an index page, you know where to go! And more, to lookup any particular Chapter that matters, you just need to look over the index page, again and again, every time. After finding the matching index you can efficiently jump to that chapter by skipping the rest.

But then, in addition to actual 1000 pages, you will need another ~10 pages to show the indices, so totally 1010 pages.

Thus, the index is a separate section that stores values of indexed column + pointer to the indexed row in a sorted order for efficient look-ups.

Things are simple in schools, isn't it? :P

Timestamp Difference In Hours for PostgreSQL

Get fields where a timestamp is greater than date in postgresql:

SELECT * from yourtable 
WHERE your_timestamp_field > to_date('05 Dec 2000', 'DD Mon YYYY');

Subtract minutes from timestamp in postgresql:

SELECT * from yourtable 
WHERE your_timestamp_field > current_timestamp - interval '5 minutes'

Subtract hours from timestamp in postgresql:

SELECT * from yourtable 
WHERE your_timestamp_field > current_timestamp - interval '5 hours'

How can I get client information such as OS and browser

There are two not bad libs for parsing user agent strings:

Start script missing error when running npm start

In my case, if it's a react project, you can try to upgrade npm, and then upgrade react-cli

npm -g install npm@version
npm install -g create-react-app

Gridview row editing - dynamic binding to a DropDownList

Quite easy... You're doing it wrong, because by that event the control is not there:

protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow && 
        (e.Row.RowState & DataControlRowState.Edit) == DataControlRowState.Edit)
    { 
        // Here you will get the Control you need like:
        DropDownList dl = (DropDownList)e.Row.FindControl("ddlPBXTypeNS");
    }
}

That is, it will only be valid for a DataRow (the actually row with data), and if it's in Edit mode... because you only edit one row at a time. The e.Row.FindControl("ddlPBXTypeNS") will only find the control that you want.

Cannot install Aptana Studio 3.6 on Windows

I'm using Win 8.1, and have installed Aptana easily, and use for PHP programming without any issues. And just experimented with Ruble enhancement to the UI. All seems to work just fine.

3.6.0.201407100658

How to force table cell <td> content to wrap?

Use table-layout:fixed in the table and word-wrap:break-word in the td.

See this example:

<html>
<head>
   <style>
   table {border-collapse:collapse; table-layout:fixed; width:310px;}
   table td {border:solid 1px #fab; width:100px; word-wrap:break-word;}
   </style>
</head>

<body>
   <table>
      <tr>
         <td>1</td>
         <td>Lorem Ipsum</td>
         <td>Lorem Ipsum is simply dummy text of the printing and typesetting industry. </td>
      </tr>
      <tr>
         <td>2</td>
         <td>LoremIpsumhasbeentheindustry'sstandarddummytexteversincethe1500s,whenanunknown</td>
         <td>Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.</td>
      </tr>
      <tr>
         <td>3</td>
         <td></td>
         <td>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna...</td>
      </tr>
   </table>
</body>
</html>

DEMO:

_x000D_
_x000D_
table {border-collapse:collapse; table-layout:fixed; width:310px;}_x000D_
       table td {border:solid 1px #fab; width:100px; word-wrap:break-word;}
_x000D_
       <table>_x000D_
          <tr>_x000D_
             <td>1</td>_x000D_
             <td>Lorem Ipsum</td>_x000D_
             <td>Lorem Ipsum is simply dummy text of the printing and typesetting industry. </td>_x000D_
          </tr>_x000D_
          <tr>_x000D_
             <td>2</td>_x000D_
             <td>LoremIpsumhasbeentheindustry'sstandarddummytexteversincethe1500s,whenanunknown</td>_x000D_
             <td>Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book.</td>_x000D_
          </tr>_x000D_
          <tr>_x000D_
             <td>3</td>_x000D_
             <td></td>_x000D_
             <td>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna...</td>_x000D_
          </tr>_x000D_
       </table>_x000D_
    
_x000D_
_x000D_
_x000D_

Getting all names in an enum as a String[]

Try this:

public static String[] vratAtributy() {
    String[] atributy = new String[values().length];
    for(int index = 0; index < atributy.length; index++) {
        atributy[index] = values()[index].toString();
    }
    return atributy;
}

How to sleep the thread in node.js without affecting other threads?

When working with async functions or observables provided by 3rd party libraries, for example Cloud firestore, I've found functions the waitFor method shown below (TypeScript, but you get the idea...) to be helpful when you need to wait on some process to complete, but you don't want to have to embed callbacks within callbacks within callbacks nor risk an infinite loop.

This method is sort of similar to a while (!condition) sleep loop, but yields asynchronously and performs a test on the completion condition at regular intervals till true or timeout.

export const sleep = (ms: number) => {
    return new Promise(resolve => setTimeout(resolve, ms))
}
/**
 * Wait until the condition tested in a function returns true, or until 
 * a timeout is exceeded.
 * @param interval The frenequency with which the boolean function contained in condition is called.
 * @param timeout  The maximum time to allow for booleanFunction to return true
 * @param booleanFunction:  A completion function to evaluate after each interval. waitFor will return true as soon as the completion function returns true.   
 */
export const waitFor = async function (interval: number, timeout: number,
    booleanFunction: Function): Promise<boolean> {
    let elapsed = 1;
    if (booleanFunction()) return true;
    while (elapsed < timeout) {
        elapsed += interval;
        await sleep(interval);
        if (booleanFunction()) {
            return true;
        }
    }
    return false;
}

The say you have a long running process on your backend you want to complete before some other task is undertaken. For example if you have a function that totals a list of accounts, but you want to refresh the accounts from the backend before you calculate, you can do something like this:

async recalcAccountTotals() : number {
     this.accountService.refresh();   //start the async process.
     if (this.accounts.dirty) {
           let updateResult = await waitFor(100,2000,()=> {return !(this.accounts.dirty)})
     }
 if(!updateResult) { 
      console.error("Account refresh timed out, recalc aborted");
      return NaN;
    }
 return ... //calculate the account total. 
}

Dynamic SQL results into temp table in SQL Stored procedure

CREATE PROCEDURE dbo.pdpd_DynamicCall 
AS
DECLARE @SQLString_2 NVARCHAR(4000)
SET NOCOUNT ON
Begin
    --- Create global temp table
    CREATE TABLE ##T1 ( column_1 varchar(10) , column_2 varchar(100) )

    SELECT @SQLString_2 = 'INSERT INTO ##T1( column_1, column_2) SELECT column_1 = "123", column_2 = "MUHAMMAD IMRON"'
    SELECT @SQLString_2 = REPLACE(@SQLString_2, '"', '''')

    EXEC SP_EXECUTESQL @SQLString_2

    --- Test Display records
    SELECT * FROM ##T1

    --- Drop global temp table 
    IF OBJECT_ID('tempdb..##T1','u') IS NOT NULL
    DROP TABLE ##T1
End

Git Push Error: insufficient permission for adding an object to repository database

After using git for a long time without problems, I encountered this problem today. After some reflection, I realized I changed my umask earlier today from 022 to something else.

All the answers by other people are helpful, i.e., do chmod for the offending directories. But the root cause is my new umask which will always cause a new problem down the road whenever a new directory is created under .git/object/. So, the long term solution for me is to change umask back to 022.

What are the different types of indexes, what are the benefits of each?

Different database systems have different names for the same type of index, so be careful with this. For example, what SQL Server and Sybase call "clustered index" is called in Oracle an "index-organised table".

Debugging with Android Studio stuck at "Waiting For Debugger" forever

Got it fixed according this solution: https://youtrack.jetbrains.com/issue/IDEA-166153
I opened <project dir>/.idea/workspace.xml replaced all the
<option name="DEBUGGER_TYPE" value="Auto" /> occurrences to
<option name="DEBUGGER_TYPE" value="Java" />
and restarted Android Studio

How to calculate percentage when old value is ZERO

How to deal with Zeros when calculating percentage changes is the researcher's call and requires some domain expertise. If the researcher believes that it would not be distorting the data, s/he may simply add a very small constant to all values to get rid of all zeros. In financial series, when dealing with trading volume, for example, we may not want to do this because trading volume = 0 just means that: the asset did not trade at all. The meaning of volume = 0 may be very different from volume = 0.00000000001. This is my preferred strategy in cases whereby I can not logically add a small constant to all values. Consider the percentage change formula ((New-Old)/Old) *100. If New = 0, then percentage change would be -100%. This number indeed makes financial sense as long as it is the minimum percentage change in the series (This is indeed guaranteed to be the minimum percentage change in the series). Why? Because it shows that trading volume experiences maximum possible decrease, which is going from any number to 0, -100%. So, I'll be fine with this value being in my percentage change series. If I normalize that series, then even better since this (possibly) relatively big number in absolute value will be analyzed on the same scale as other variables are. Now, what if the Old value = 0. That's a trickier case. Percentage change due to going from 0 to 1 will be equal to that due to going from 0 to a million: infinity. The fact that we call both "infinity" percentage change is problematic. In this case, I would set the infinities equal to np.nan and interpolate them.

The following graph shows what I discussed above. Starting from series 1, we get series 4, which is ready to be analyzed, with no Inf or NaNs.

enter image description here

One more thing: a lot of the time, the reason for calculating percentage change is to stationarize the data. So, if your original series contains zero and you wish to convert it to percentage change to achieve stationarity, first make sure it is not already stationary. Because if it is, you don't have to calculate percentage change. The point is that series that take the value of 0 a lot (the problem OP has) are very likely to be already stationary, for example the volume series I considered above. Imagine a series oscillating above and below zero, thus hitting 0 at times. Such a series is very likely already stationary.

How to get a MemoryStream from a Stream in .NET?

Use this:

var memoryStream = new MemoryStream();
stream.CopyTo(memoryStream);

This will convert Stream to MemoryStream.

How can I generate an MD5 hash?

There is a DigestUtils class in Spring also:

http://static.springsource.org/spring/docs/3.0.x/javadoc-api/org/springframework/util/DigestUtils.html

This class contains the method md5DigestAsHex() that does the job.

Credit card payment gateway in PHP?

There are more than a few gateways out there, but I am not aware of a reliable gateway that is free. Most gateways like PayPal will provide you APIs that will allow you to process credit cards, as well as do things like void, charge, or refund.

The other thing you need to worry about is the coming of PCI compliance which basically says if you are not compliant, you (or the company you work for) will be liable by your Merchant Bank and/or Card Vendor for not being compliant by July of 2010. This will impose large fines on you and possibly revoke the ability for you to process credit cards.

All that being said companies like PayPal have a PHP SDK:

https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/library_download_sdks

Authorize.Net:

http://developer.authorize.net/samplecode/

Those are two of the more popular ones for the United States.

For PCI Info see:

https://www.pcisecuritystandards.org/

Can't find the 'libpq-fe.h header when trying to install pg gem

For MacOS without installing PostgreSQL server:

brew install libpq
gem install pg -- --with-pg-config="/usr/local/Cellar/libpq/9.6.6/bin/pg_config"

Visual Studio can't 'see' my included header files

If the visual studio says that you miss some file in the current source file folder, there is one solution that i used. Just right click the file you want to add and choose Open Document, if it really doesn't exist, then you should see something like cannot find file in the source file path = "somewhere in your computer", then what you could do is the add your source file into that path first and see if it works.

How to create localhost database using mysql?

See here for starting the service and here for how to make it permanent. In short to test it, open a "DOS" terminal with administrator privileges and write:

shell> "C:\Program Files\MySQL\[YOUR MYSQL VERSION PATH]\bin\mysqld"

Python: How to check if keys exists and retrieve value from Dictionary in descending priority

One option if the number of keys is small is to use chained gets:

value = myDict.get('lastName', myDict.get('firstName', myDict.get('userName')))

But if you have keySet defined, this might be clearer:

value = None
for key in keySet:
    if key in myDict:
        value = myDict[key]
        break

The chained gets do not short-circuit, so all keys will be checked but only one used. If you have enough possible keys that that matters, use the for loop.

VBA Macro to compare all cells of two Excel files

A very simple check you can do with Cell formulas:

Sheet 1 (new - old)

=(if(AND(Ref_New<>"";Ref_Old="");Ref_New;"")

Sheet 2 (old - new)

=(if(AND(Ref_Old<>"";Ref_New="");Ref_Old;"")

This formulas should work for an ENGLISH Excel. For other languages they need to be translated. (For German i can assist)

You need to open all three Excel Documents, then copy the first formula into A1 of your sheet 1 and the second into A1 of sheet 2. Now click in A1 of the first cell and mark "Ref_New", now you can select your reference, go to the new file and click in the A1, go back to sheet1 and do the same for "Ref_Old" with the old file. Replace also the other "Ref_New".

Doe the same for Sheet two.

Now copy the formaula form A1 over the complete range where zour data is in the old and the new file.

But two cases are not covered here:

  1. In the compared cell of New and Old is the same data (Resulting Cell will be empty)
  2. In the compared cell of New and Old is diffe data (Resulting Cell will be empty)

To cover this two cases also, you should create your own function, means learn VBA. A very useful Excel page is cpearson.com

How do I decode a string with escaped unicode?

Edit (2017-10-12):

@MechaLynx and @Kevin-Weber note that unescape() is deprecated from non-browser environments and does not exist in TypeScript. decodeURIComponent is a drop-in replacement. For broader compatibility, use the below instead:

decodeURIComponent(JSON.parse('"http\\u00253A\\u00252F\\u00252Fexample.com"'));
> 'http://example.com'

Original answer:

unescape(JSON.parse('"http\\u00253A\\u00252F\\u00252Fexample.com"'));
> 'http://example.com'

You can offload all the work to JSON.parse

document.getElementById().value doesn't set the value

Try using ,

$('#points').val(request.responseText);

Laravel csrf token mismatch for ajax POST Request

I just use @csrf inside the form and its working fine

What is the "Temporary ASP.NET Files" folder for?

Thats where asp.net puts dynamically compiled assemblies.

How to play a notification sound on websites?

As of 2016, the following will suffice (you don't even need to embed):

let src = 'https://file-examples.com/wp-content/uploads/2017/11/file_example_MP3_700KB.mp3';
let audio = new Audio(src);
audio.play();

See more here.

Redirect all to index.php using htaccess

You can use something like this:

RewriteEngine on
RewriteRule ^.+$ /index.php [L]

This will redirect every query to the root directory's index.php. Note that it will also redirect queries for files that exist, such as images, javascript files or style sheets.

Deprecation warning in Moment.js - Not in a recognized ISO format

You can use

moment(date,"currentFormat").format("requiredFormat");

This should be used when date is not ISO Format as it'll tell moment what our current format is.

"Couldn't read dependencies" error with npm

I got the same exception also, but it was previously running fine in another machine. Anyway above solution didn't worked for me. What i did to resolve it?

  1. Copy dependencies list into clipboard.
  2. enter "npm init" to create fresh new package.json
  3. Paste the dependencies again back to package.json
  4. run "npm install" again!

Done :) Hope it helps.

How to dismiss keyboard iOS programmatically when pressing return

for swift 3-4 i fixed like

func textFieldShouldBeginEditing(_ textField: UITextField) -> Bool {
    return false
}

just copy paste anywhere on the class. This solution just work if you want all UItextfield work as same, or if you have just one!

How do you dynamically add elements to a ListView on Android?

Code for MainActivity.java file.

public class MainActivity extends Activity {

    ListView listview;
    Button Addbutton;
    EditText GetValue;
    String[] ListElements = new String[] {
        "Android",
        "PHP"
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listview = (ListView) findViewById(R.id.listView1);
        Addbutton = (Button) findViewById(R.id.button1);
        GetValue = (EditText) findViewById(R.id.editText1);

        final List < String > ListElementsArrayList = new ArrayList < String >
            (Arrays.asList(ListElements));


        final ArrayAdapter < String > adapter = new ArrayAdapter < String >
            (MainActivity.this, android.R.layout.simple_list_item_1,
                ListElementsArrayList);

        listview.setAdapter(adapter);

        Addbutton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                ListElementsArrayList.add(GetValue.getText().toString());
                adapter.notifyDataSetChanged();
            }
        });
    }
}

Code for activity_main.xml layout file.

<RelativeLayout 
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:paddingBottom="@dimen/activity_vertical_margin"
  android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  tools:context="com.listviewaddelementsdynamically_android_examples
    .com.MainActivity" >

  <Button
    android:id="@+id/button1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/editText1"
    android:layout_centerHorizontal="true"
    android:text="ADD Values to listview" />

  <EditText
    android:id="@+id/editText1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="26dp"
    android:ems="10"
    android:hint="Add elements listView" />

  <ListView
    android:id="@+id/listView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/button1"
    android:layout_centerHorizontal="true" >
  </ListView>

</RelativeLayout>

ScreenShot

enter image description here

Django Forms: if not valid, show form with error message

You can put simply a flag variable, in this case is_successed.

def preorder_view(request, pk, template_name='preorders/preorder_form.html'):
    is_successed=0
    formset = PreorderHasProductsForm(request.POST)
    client= get_object_or_404(Client, pk=pk)
    if request.method=='POST':
        #populate the form with data from the request
       # formset = PreorderHasProductsForm(request.POST)
        if formset.is_valid():
            is_successed=1
            preorder_date=formset.cleaned_data['preorder_date']
            product=formset.cleaned_data['preorder_has_products']
            return render(request, template_name, {'preorder_date':preorder_date,'product':product,'is_successed':is_successed,'formset':formset})



    return render(request, template_name, {'object':client,'formset':formset})

afterwards in your template you can just put the code below

{%if is_successed == 1 %}
<h1>{{preorder_date}}</h1>
<h2> {{product}}</h2>
{%endif %}

List all environment variables from the command line

Just do:

SET

You can also do SET prefix to see all variables with names starting with prefix.

For example, if you want to read only derbydb from the environment variables, do the following:

set derby 

...and you will get the following:

DERBY_HOME=c:\Users\amro-a\Desktop\db-derby-10.10.1.1-bin\db-derby-10.10.1.1-bin