Programs & Examples On #Mnemonics

How to show only next line after the matched one?

Many good answers have been given to this question so far, but I still miss one with awk not using getline. Since, in general, it is not necessary to use getline, I would go for:

awk ' f && NR==f+1; /blah/ {f=NR}' file  #all matches after "blah"


awk '/blah/ {f=NR} f && NR==f+1' file   #matches after "blah" not being also "blah"

The logic always consists in storing the line where "blah" is found and then printing those lines that are one line after.


Sample file:

$ cat a

Get all the lines after "blah". This prints another "blah" if it appears after the first one.

$ awk 'f&&NR==f+1; /blah/ {f=NR}' a

Get all the lines after "blah" if they do not contain "blah" themselves.

$ awk '/blah/ {f=NR} f && NR==f+1' a

What is the difference between "word-break: break-all" versus "word-wrap: break-word" in CSS

The W3 specification that talks about these seem to suggest that word-break: break-all is for requiring a particular behaviour with CJK (Chinese, Japanese, and Korean) text, whereas word-wrap: break-word is the more general, non-CJK-aware, behaviour.

How to print Unicode character in Python?

I use Portable winpython in Windows, it includes IPython QT console, I could achieve the following.

>>>print ("??")

>>>print ("????")

>>>str = "??"

>>>print (str)

your console interpreter should support unicode in order to show unicode characters.

Polymorphism vs Overriding vs Overloading

The clearest way to express polymorphism is via an abstract base class (or interface)

public abstract class Human{
   public abstract void goPee();

This class is abstract because the goPee() method is not definable for Humans. It is only definable for the subclasses Male and Female. Also, Human is an abstract concept — You cannot create a human that is neither Male nor Female. It’s got to be one or the other.

So we defer the implementation by using the abstract class.

public class Male extends Human{
    public void goPee(){
        System.out.println("Stand Up");


public class Female extends Human{
    public void goPee(){
        System.out.println("Sit Down");

Now we can tell an entire room full of Humans to go pee.

public static void main(String[] args){
    ArrayList<Human> group = new ArrayList<Human>();
    group.add(new Male());
    group.add(new Female());
    // ... add more...

    // tell the class to take a pee break
    for (Human person : group) person.goPee();

Running this would yield:

Stand Up
Sit Down

Multiple actions were found that match the request in Web Api

I know it is an old question, but sometimes, when you use service resources like from AngularJS to connect to WebAPI, make sure you are using the correct route, other wise this error happens.

how to setup ssh keys for jenkins to publish via ssh

You will need to create a public/private key as the Jenkins user on your Jenkins server, then copy the public key to the user you want to do the deployment with on your target server.

Step 1, generate public and private key on build server as user jenkins

build1:~ jenkins$ whoami
build1:~ jenkins$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/var/lib/jenkins/.ssh/id_rsa): 
Created directory '/var/lib/jenkins/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /var/lib/jenkins/.ssh/id_rsa.
Your public key has been saved in /var/lib/jenkins/.ssh/
The key fingerprint is:
The key's randomart image is:
build1:~ jenkins$ ls -l .ssh
total 2
-rw-------  1 jenkins  jenkins  1679 Feb 28 11:55 id_rsa
-rw-r--r--  1 jenkins  jenkins   411 Feb 28 11:55 
build1:~ jenkins$ cat .ssh/
ssh-rsa AAAlskdjfalskdfjaslkdjf... [email protected]

Step 2, paste the pub file contents onto the target server.

target:~ bob$ cd .ssh
target:~ bob$ vi authorized_keys (paste in the stuff which was output above.)

Make sure your .ssh dir has permissoins 700 and your authorized_keys file has permissions 644

Step 3, configure Jenkins

  1. In the jenkins web control panel, nagivate to "Manage Jenkins" -> "Configure System" -> "Publish over SSH"
  2. Either enter the path of the file e.g. "var/lib/jenkins/.ssh/id_rsa", or paste in the same content as on the target server.
  3. Enter your passphrase, server and user details, and you are good to go!

ES6 export all values from object

I just had need to do this for a config file.

var config = {
    x: "CHANGE_ME",
    y: "CHANGE_ME",
    z: "CHANGE_ME"

export default config;

You can do it like this

import { default as config } from "./config";

console.log(config.x); // CHANGE_ME

This is using Typescript mind you.

how to fix stream_socket_enable_crypto(): SSL operation failed with code 1

Editor's note: disabling SSL verification has security implications. Without verification of the authenticity of SSL/HTTPS connections, a malicious attacker can impersonate a trusted endpoint such as Gmail, and you'll be vulnerable to a Man-in-the-Middle Attack.

Be sure you fully understand the security issues before using this as a solution.

You can add below code in /config/mail.php ( tested and worked on laravel 5.1, 5.2, 5.4 )

'stream' => [
   'ssl' => [
      'allow_self_signed' => true,
      'verify_peer' => false,
      'verify_peer_name' => false,

How to verify CuDNN installation?

On Ubuntu 20.04LTS:

cat /usr/local/cuda/include/cudnn_version.h | grep CUDNN_MAJOR

returned the expected results

jQuery override default validation error message display (Css) Popup/Tooltip like

Add following css to your .validate method to change the css or functionality

 errorElement: "div",
    wrapper: "div",
    errorPlacement: function(error, element) {
        offset = element.offset();

How do I convert a column of text URLs into active hyperlinks in Excel?

For me I just copied the entire column which has the URLs in text format into another application (say Evernote), and when they were pasted there they became links, and then I just copied them back into Excel.

The only thing here is you need to make sure the data you copy back lines up with the rest of the columns.

Oracle "ORA-01008: not all variables bound" Error w/ Parameters

You might also consider removing the need for duplicated parameter names in your Sql by changing your Sql to

table.Variable2 LIKE '%' || :VarB || '%'

and then getting your client to provide '%' for any value of VarB instead of null. In some ways I think this is more natural.

You could also change the Sql to

table.Variable2 LIKE '%' || IfNull(:VarB, '%') || '%'

Select every Nth element in CSS

You need the correct argument for the nth-child pseudo class.

  • The argument should be in the form of an + b to match every ath child starting from b.

  • Both a and b are optional integers and both can be zero or negative.

    • If a is zero then there is no "every ath child" clause.
    • If a is negative then matching is done backwards starting from b.
    • If b is zero or negative then it is possible to write equivalent expression using positive b e.g. 4n+0 is same as 4n+4. Likewise 4n-1 is same as 4n+3.


Select every 4th child (4, 8, 12, ...)

li:nth-child(4n) {_x000D_
  background: yellow;_x000D_

Select every 4th child starting from 1 (1, 5, 9, ...)

li:nth-child(4n+1) {_x000D_
  background: yellow;_x000D_

Select every 3rd and 4th child from groups of 4 (3 and 4, 7 and 8, 11 and 12, ...)

/* two selectors are required */_x000D_
li:nth-child(4n+4) {_x000D_
  background: yellow;_x000D_

Select first 4 items (4, 3, 2, 1)

/* when a is negative then matching is done backwards  */_x000D_
li:nth-child(-n+4) {_x000D_
  background: yellow;_x000D_

'if' statement in jinja2 template

We need to remember that the {% endif %} comes after the {% else %}.

So this is an example:

{% if someTest %}
     <p> Something is True </p>
{% else %}
     <p> Something is False </p>
{% endif %}

Difference between number and integer datatype in oracle dictionary views

the best explanation i've found is this:

What is the difference betwen INTEGER and NUMBER? When should we use NUMBER and when should we use INTEGER? I just wanted to update my comments here...

NUMBER always stores as we entered. Scale is -84 to 127. But INTEGER rounds to whole number. The scale for INTEGER is 0. INTEGER is equivalent to NUMBER(38,0). It means, INTEGER is constrained number. The decimal place will be rounded. But NUMBER is not constrained.

  • INTEGER(12.2) => 12
  • INTEGER(12.5) => 13
  • INTEGER(12.9) => 13
  • INTEGER(12.4) => 12
  • NUMBER(12.2) => 12.2
  • NUMBER(12.5) => 12.5
  • NUMBER(12.9) => 12.9
  • NUMBER(12.4) => 12.4

INTEGER is always slower then NUMBER. Since integer is a number with added constraint. It takes additional CPU cycles to enforce the constraint. I never watched any difference, but there might be a difference when we load several millions of records on the INTEGER column. If we need to ensure that the input is whole numbers, then INTEGER is best option to go. Otherwise, we can stick with NUMBER data type.

Here is the link

Difference between two dates in years, months, days in JavaScript

I know it is an old thread, but I'd like to put my 2 cents based on the answer by @Pawel Miech.

It is true that you need to convert the difference into milliseconds, then you need to make some math. But notice that, you need to do the math in backward manner, i.e. you need to calculate years, months, days, hours then minutes.

I used to do some thing like this:

    var mins;
    var hours;
    var days;
    var months;
    var years;

    var diff = new Date() - new Date(yourOldDate);  
// yourOldDate may be is coming from DB, for example, but it should be in the correct format ("MM/dd/yyyy hh:mm:ss:fff tt")

    years = Math.floor((diff) / (1000 * 60 * 60 * 24 * 365));
    diff = Math.floor((diff) % (1000 * 60 * 60 * 24 * 365));
    months = Math.floor((diff) / (1000 * 60 * 60 * 24 * 30));
    diff = Math.floor((diff) % (1000 * 60 * 60 * 24 * 30));
    days = Math.floor((diff) / (1000 * 60 * 60 * 24));
    diff = Math.floor((diff) % (1000 * 60 * 60 * 24));
    hours = Math.floor((diff) / (1000 * 60 * 60));
    diff = Math.floor((diff) % (1000 * 60 * 60));
    mins = Math.floor((diff) / (1000 * 60));

But, of course, this is not precise because it assumes that all years have 365 days and all months have 30 days, which is not true in all cases.

How do I perform a JAVA callback between classes?

IMO, you should have a look at the Observer Pattern, and this is how most of the listeners work

git diff file against its last change

This does exist, but it's actually a feature of git log:

git log -p [--follow] [-1] <path>

Note that -p can also be used to show the inline diff from a single commit:

git log -p -1 <commit>

Options used:

  • -p (also -u or --patch) is hidden deeeeeeeep in the git-log man page, and is actually a display option for git-diff. When used with log, it shows the patch that would be generated for each commit, along with the commit information—and hides commits that do not touch the specified <path>. (This behavior is described in the paragraph on --full-diff, which causes the full diff of each commit to be shown.)
  • -1 shows just the most recent change to the specified file (-n 1 can be used instead of -1); otherwise, all non-zero diffs of that file are shown.
  • --follow is required to see changes that occurred prior to a rename.

As far as I can tell, this is the only way to immediately see the last set of changes made to a file without using git log (or similar) to either count the number of intervening revisions or determine the hash of the commit.

To see older revisions changes, just scroll through the log, or specify a commit or tag from which to start the log. (Of course, specifying a commit or tag returns you to the original problem of figuring out what the correct commit or tag is.)

Credit where credit is due:

  • I discovered log -p thanks to this answer.
  • Credit to FranciscoPuga and this answer for showing me the --follow option.
  • Credit to ChrisBetti for mentioning the -n 1 option and atatko for mentioning the -1 variant.
  • Credit to sweaver2112 for getting me to actually read the documentation and figure out what -p "means" semantically.

How do I uniquely identify computers visiting my web site?

There is only a small amount of information that you can get via an HTTP connection.

  1. IP - But as others have said, this is not fixed for many, if not most Internet users due to their ISP's dynamic allocation policies.

  2. Useragent String - Nearly all browsers send what kind of browser they are with every request. However, this can be set by the user in many browsers today.

  3. Collection of request fields - There are other fields sent with each request, such as supported encodings, etc. These, if used in the aggregate can help to ID a user's machine, but again are browser dependent and can be changed.

  4. Cookies - Setting a cookie is another way to identify a machine, or more specifically a browser on a machine, but as others have said, these can be deleted, or turned off by the users, and are only applicable on a browser, not a machine.

So, the correct response is that you cannot achieve what you would live via the HTTP over IP protocols alone. However, using a combination of cookies, as well as IP, and the fields in the HTTP request, you have a good chance at guessing, sort of, what machine it is. Users tend to use only one browser, and often from one machine, so this may be fairly relieable, but this will vary depending on the audience...techies are more likely to mess with this stuff, and use more machines/browsers. Additionally, this could even be coupled with some attempt to geo-locate the IP, and use that data as well. But in any case, there is no solution that will be correct all of the time.

Convert JS Object to form data

This function adds all data from object to FormData

ES6 version from @developer033:

function buildFormData(formData, data, parentKey) {
  if (data && typeof data === 'object' && !(data instanceof Date) && !(data instanceof File)) {
    Object.keys(data).forEach(key => {
      buildFormData(formData, data[key], parentKey ? `${parentKey}[${key}]` : key);
  } else {
    const value = data == null ? '' : data;

    formData.append(parentKey, value);

function jsonToFormData(data) {
  const formData = new FormData();
  buildFormData(formData, data);
  return formData;

const my_data = {
  num: 1,
  falseBool: false,
  trueBool: true,
  empty: '',
  und: undefined,
  nullable: null,
  date: new Date(),
  name: 'str',
  another_object: {
    name: 'my_name',
    value: 'whatever'
  array: [
      key1: {
        name: 'key1'


jQuery version:

function appendFormdata(FormData, data, name){
    name = name || '';
    if (typeof data === 'object'){
        $.each(data, function(index, value){
            if (name == ''){
                appendFormdata(FormData, value, index);
            } else {
                appendFormdata(FormData, value, name + '['+index+']');
    } else {
        FormData.append(name, data);

var formData = new FormData(),
    your_object = {
        name: 'test object',
        another_object: {
            name: 'and other objects',
            value: 'whatever'
appendFormdata(formData, your_object); 

Python: Random numbers into a list

xrange() will not work for 3.x.

numpy.random.randint().tolist() is a great alternative for integers in a specified interval:

import numpy as np
np.random.seed(123) #option for reproducibility
np.random.randint(low=0, high=100, size=10).tolist()


[66, 92, 98, 17, 83, 57, 86, 97, 96, 47]

You also have np.random.uniform() for floats:

np.random.uniform(low=0, high=100, size=10).tolist()


How to count the frequency of the elements in an unordered list?

i'm using Counter to generate a freq. dict from text file words in 1 line of code

def _fileIndex(fh):
''' create a dict using Counter of a
flat list of words (re.findall(re.compile(r"[a-zA-Z]+"), lines)) in (lines in file->for lines in fh)
return Counter(
    [wrd.lower() for wrdList in
     [words for words in
      [re.findall(re.compile(r'[a-zA-Z]+'), lines) for lines in fh]]
     for wrd in wrdList])

How to remove pip package after deleting it manually

packages installed using pip can be uninstalled completely using

pip uninstall <package>

refrence link

pip uninstall is likely to fail if the package is installed using python install as they do not leave behind metadata to determine what files were installed.

packages still show up in pip list if their paths(.pth file) still exist in your site-packages or dist-packages folder. You'll need to remove them as well in case you're removing using rm -rf

What are the differences between Mustache.js and Handlebars.js?

—In addition to using "this" for handlebars, and the nested variable within variable block for mustache, you can also use the nested dot in a block for mustache:

    {{#variable}}<span class="text">{{.}}</span>{{/variable}}

Using Ansible set_fact to create a dictionary from register results

Thank you Phil for your solution; in case someone ever gets in the same situation as me, here is a (more complex) variant:

# this is just to avoid a call to |default on each iteration
- set_fact:
    postconf_d: {}

- name: 'get postfix default configuration'
  command: 'postconf -d'
  register: command

# the answer of the command give a list of lines such as:
# "key = value" or "key =" when the value is null
- name: 'set postfix default configuration as fact'
    postconf_d: >
        postconf_d |
          dict([ item.partition('=')[::2]|map('trim') ])
  with_items: command.stdout_lines

This will give the following output (stripped for the example):

"postconf_d": {
    "alias_database": "hash:/etc/aliases", 
    "alias_maps": "hash:/etc/aliases, nis:mail.aliases",
    "allow_min_user": "no", 
    "allow_percent_hack": "yes"

Going even further, parse the lists in the 'value':

- name: 'set postfix default configuration as fact'
    postconf_d: >-
      {% set key, val = item.partition('=')[::2]|map('trim') -%}
      {% if ',' in val -%}
        {% set val = val.split(',')|map('trim')|list -%}
      {% endif -%}
      {{ postfix_default_main_cf | combine({key: val}) }}
  with_items: command.stdout_lines
"postconf_d": {
    "alias_database": "hash:/etc/aliases", 
    "alias_maps": [
    "allow_min_user": "no", 
    "allow_percent_hack": "yes"

A few things to notice:

  • in this case it's needed to "trim" everything (using the >- in YAML and -%} in Jinja), otherwise you'll get an error like:

    FAILED! => {"failed": true, "msg": "|combine expects dictionaries, got u\"  {u'...
  • obviously the {% if .. is far from bullet-proof

  • in the postfix case, val.split(',')|map('trim')|list could have been simplified to val.split(', '), but I wanted to point out the fact you will need to |list otherwise you'll get an error like:

    "|combine expects dictionaries, got u\"{u'...': <generator object do_map at ...

Hope this can help.

How to center buttons in Twitter Bootstrap 3?

I had this problem. I used

<div class = "col-xs-8 text-center">

On my div containing a few h3 lines, a couple h4 lines and a Bootstrap button. Everything besides the button jumped to the center after I used text-center so I went into my CSS sheet overriding Bootstrap and gave the button a

margin: auto;

which seems to have solved the problem.

How to Install Sublime Text 3 using Homebrew

$ brew tap caskroom/cask
$ brew install brew-cask
$ brew tap caskroom/versions
$ brew cask install sublime-text

Formatting doubles for output in C#

The answer to this is simple and can be found on MSDN

Remember that a floating-point number can only approximate a decimal number, and that the precision of a floating-point number determines how accurately that number approximates a decimal number. By default, a Double value contains 15 decimal digits of precision, although a maximum of 17 digits is maintained internally.

In your example, the value of i is 6.89999999999999946709 which has the number 9 for all positions between the 3rd and the 16th digit (remember to count the integer part in the digits). When converting to string, the framework rounds the number to the 15th digit.

i     = 6.89999999999999 946709
digit =           111111 111122
        1 23456789012345 678901

Best way to overlay an ESRI shapefile on google maps?

2018 already... I've found this fantastic online tool to convert from ESRI shapefiles to SVG, TopoJSON, GeoJSON.

Here is the explanation of how to use it

Fast and straightforward! :)

Update OpenSSL on OS X with Homebrew

  1. install port:
  2. install or upgrade openssl package: sudo port install openssl or sudo port upgrade openssl
  3. that's it, run openssl version to see the result.

How to configure Glassfish Server in Eclipse manually

To use Glassfish tools with Eclipse Luna you need Java 8. I also faced this problem because I had Java 7. If you have Java 7 in your environment then download eclipse Kepler. It will work fine.

Improve subplot size/spacing with many subplots in matplotlib

You could try the subplot_tool()


ORA-00054: resource busy and acquire with NOWAIT specified

Depending on your situation, the table being locked may just be part of a normal operation & you don't want to just kill the blocking transaction. What you want to do is have your statement wait for the other resource. Oracle 11g has DDL timeouts which can be set to deal with this.

If you're dealing with 10g then you have to get more creative and write some PL/SQL to handle the re-try. Look at Getting around ORA-00054 in Oracle 10g This re-runs your statement when a resource_busy exception occurs.

How to refresh activity after changing language (Locale) inside application

The way we have done it was using Broadcasts:

  1. Send the broadcast every time the user changes language
  2. Register the broadcast receiver in the AppActivity.onCreate() and unregister in AppActivity.onDestroy()
  3. In BroadcastReceiver.onReceive() just restart the activity.

AppActivity is the parent activity which all other activities subclass.

Below is the snippet from my code, not tested outside the project, but should give you a nice idea.

When the user changes the language

sendBroadcast(new Intent("Language.changed"));

And in the parent activity

public class AppActivity extends Activity {

     * The receiver that will handle the change of the language.
    private BroadcastReceiver mLangaugeChangedReceiver;

    protected void onCreate(final Bundle savedInstanceState) {

        // ...
        // Other code here
        // ...

        // Define receiver
        mLangaugeChangedReceiver = new BroadcastReceiver() {

            public void onReceive(final Context context, final Intent intent) {

        // Register receiver
        registerReceiver(mLangaugeChangedReceiver, new IntentFilter("Language.changed"));

    protected void onDestroy() {

        // ...
        // Other cleanup code here
        // ...

        // Unregister receiver
        if (mLangaugeChangedReceiver != null) {
            try {
                mLangaugeChangedReceiver = null;
            } catch (final Exception e) {}

This will also refresh the activity which changed the language (if it subclasses the above activity).

This will make you lose any data, but if it is important you should already have taken care of this using Actvity.onSaveInstanceState() and Actvity.onRestoreInstanceState() (or similar).

Let me know your thoughts about this.


Amazon S3 and Cloudfront cache, how to clear cache or synchronize their cache

As to the actual code

get your CloudFront distribution id

aws cloudfront list-distributions

Invalidate all files in the distribution, so CloudFront fetches fresh ones

aws cloudfront create-invalidation --distribution-id=S11A16G5KZMEQD --paths /

My actual full release script is

#!/usr/bin/env bash

export AWS_ACCESS_KEY_ID=xxxxxxxxxxx
export AWS_SECRET_ACCESS_KEY=xxxxxxxxx
export AWS_DEFAULT_REGION=eu-west-1

echo "Building production"
if npm run build:prod ; then
   echo "Build Successful"
  echo "exiting.."
  exit 1

echo "Removing all files on bucket"
aws s3 rm s3://${BUCKET} --recursive

echo "Attempting to upload site .."
echo "Command:  aws s3  sync $SOURCE_DIR s3://$BUCKET/"
aws s3  sync ${SOURCE_DIR} s3://${BUCKET}/
echo "S3 Upload complete"

echo "Invalidating cloudfrond distribution to get fresh cache"
aws cloudfront create-invalidation --distribution-id=S11A16G5KZMEQD --paths / --profile=myawsprofile

echo "Deployment complete"  


Node.js, can't open files. Error: ENOENT, stat './path/to/file'

Here the code to use your app.js

input specifies file name'/'+input);

SQL - How do I get only the numbers after the decimal?

X - TRUNC(X), works for negatives too.

It would give you the decimal part of the number, as a double, not an integer.

Copy a table from one database to another in Postgres

To move a table from database A to database B at your local setup, use the following command:

pg_dump -h localhost -U owner-name -p 5432 -C -t table-name database1 | psql -U owner-name -h localhost -p 5432 database2

How to set a Postgresql default value datestamp like 'YYYYMM'?

Just in case Milen A. Radev doesn't get around to posting his solution, this is it:

    key     int PRIMARY KEY,

Posting form to different MVC post action depending on the clicked submit button


ActionNameSelectorAttribute mentioned in

  1. How do you handle multiple submit buttons in ASP.NET MVC Framework?

  2. ASP.Net MVC 4 Form with 2 submit buttons/actions


Reference: dotnet-tricks - Handling multiple submit buttons on the same form - MVC Razor

Second Approach

Adding a new Form for handling Cancel button click. Now, on Cancel button click we will post the second form and will redirect to the home page.

Third Approach: Client Script

<button name="ClientCancel" type="button" 
    onclick=" document.location.href = $('#cancelUrl').attr('href');">Cancel (Client Side)
<a id="cancelUrl" href="@Html.AttributeEncode(Url.Action("Index", "Home"))" 

SQL Insert Query Using C#

public static string textDataSource = "Data Source=localhost;Initial 
Catalog=TEST_C;User ID=sa;Password=P@ssw0rd";
public static bool ExtSql(string sql) {
    SqlConnection cnn;
    SqlCommand cmd;
    cnn = new SqlConnection(textDataSource);
    cmd = new SqlCommand(sql, cnn);
    try {
        return true;
    catch (Exception) {
        return false;
    finally {
        cnn = null;
        cmd = null; 

Error - Unable to access the IIS metabase

One more thing you could try:

  • Check if you have pending Windows updates.
  • If you do, please reboot before trying anything else.

I tend to never shut down my machine, so I had plenty of them waiting for a reboot. And that fixed it.

How to fix an UnsatisfiedLinkError (Can't find dependent libraries) in a JNI project

I want to inform this interesting case, after tried all the above method, the error is still there. The weird thing is it works on a Windows 7 computer, but on Windows XP it is not. Then I use dependency walker and found on the Windows XP there is no VC++ Runtime as my dll requirement. After installing VC++ Runtime package here it works like a charm. The thing that disturbed me is it keeps telling Can't find dependent libraries, while intuitively the JNI dependent dll is there, however it finally turns out the JNI dependent dll requires another dependent dl. I hope this helps.

Pandas: Subtracting two date columns and the result being an integer

How about:

df_test['Difference'] = (df_test['First_Date'] - df_test['Second Date']).dt.days

This will return difference as int if there are no missing values(NaT) and float if there is.

Restore the mysql database from .frm files

create a new database with same name copy the .frm .ibd files into xampp/mysql/data/[databasename]/

you will need ibdata file as well which is found inside

xampp/mysql/data/ copy the previous ibdata1 file paste in the paste the file and replace it with the existing ibdata file

[caution: you may loose the contents of the database which are newly created in the new ibdata file]

SQL Row_Number() function in Where Clause

I feel like all the answers showing use of a CTE or Sub Query are sufficient fixes for this, but I don't see anyone getting to the heart of why OP has a problem. The reason why what OP suggested doesn't work is due to logical query processing order here:

  1. FROM
  2. ON
  3. JOIN
  4. WHERE
  10. ORDER BY
  11. TOP

I believe this contributes to the answer greatly, because it explains why issues like this one occur. WHERE is always processed before SELECT making a CTE or Sub Query necessary for many functions. You will see this a lot in SQL Server.

import module from string variable

Apart from using the importlib one can also use exec method to import a module from a string variable.

Here I am showing an example of importing the combinations method from itertools package using the exec method:


    import_str = "from {0} import {1}".format(ITEM[0],', '.join(str(i) for i in ITEM[1:]))

ar = list(combinations([1, 2, 3, 4], 2))
for elements in ar:


(1, 2)
(1, 3)
(1, 4)
(2, 3)
(2, 4)
(3, 4)

MySQL & Java - Get id of the last inserted value (JDBC)

Alternatively you can do:

Statement stmt = db.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
numero = stmt.executeUpdate();

ResultSet rs = stmt.getGeneratedKeys();
if ({

But use Sean Bright's answer instead for your scenario.

In Flask, What is request.args and how is it used?

It has some interesting behaviour in some cases that is good to be aware of:

from werkzeug.datastructures import MultiDict

d = MultiDict([("ex1", ""), ("ex2", None)])

d.get("ex1", "alternive")
# returns: ''

d.get("ex2", "alternative")
# returns no visible output of any kind
# It is returning literally None, so if you do:
d.get("ex2", "alternative") is None
# it returns: True

d.get("ex3", "alternative")
# returns: 'alternative'

Google Maps how to Show city or an Area outline

i was looking for the same and found the answer,

solution is to use the styled map, on below link you can create your custom styles through wizard and test is at the same time google map style wizard

you can check all available options : here

here is my sample code which creates boundary for states and hide all the road and there labels.

    var styles = [
    "featureType": "administrative.province",
    "elementType": "geometry.stroke",
    "stylers": [
      { "visibility": "on" },
      { "weight": 2.5 },
      { "color": "#24b0e2" }
    "featureType": "road",
    "elementType": "geometry",
    "stylers": [
      { "visibility": "off" }
    "featureType": "administrative.locality",
    "stylers": [
      { "visibility": "off" }
    "featureType": "road",
    "elementType": "labels",
    "stylers": [
      { "visibility": "off" }

  var  geocoder = new google.maps.Geocoder();
       'address': "rajasthan"
   }, (results, status)=> {
     var mapOpts = {
       mapTypeId: google.maps.MapTypeId.ROADMAP,
       scaleControl: true,
       scrollwheel: false,
       center: results[0].geometry.location,
     map = new google.maps.Map(document.getElementById("map"), mapOpts);

Remove specific rows from a data frame

 X <- data.frame(Variable1=c(11,14,12,15),Variable2=c(2,3,1,4))
> X
  Variable1 Variable2
1        11         2
2        14         3
3        12         1
4        15         4
> X[X$Variable1!=11 & X$Variable1!=12, ]
  Variable1 Variable2
2        14         3
4        15         4
> X[ ! X$Variable1 %in% c(11,12), ]
  Variable1 Variable2
2        14         3
4        15         4

You can functionalize this however you like.

Call Javascript onchange event by programmatically changing textbox value

You're population is from the server-side. Using the registerclientscript will put the script at the beginning of the form.. you'll want to use RegisterStartupScript(Block) to have the script placed at the end of the page in question.

The former tries to run the script before the text area exists in the dom, the latter will run the script after that element in the page is created.

How to post data in PHP using file_get_contents?

Sending an HTTP POST request using file_get_contents is not that hard, actually : as you guessed, you have to use the $context parameter.

There's an example given in the PHP manual, at this page : HTTP context options (quoting) :

$postdata = http_build_query(
        'var1' => 'some content',
        'var2' => 'doh'

$opts = array('http' =>
        'method'  => 'POST',
        'header'  => 'Content-Type: application/x-www-form-urlencoded',
        'content' => $postdata

$context  = stream_context_create($opts);

$result = file_get_contents('', false, $context);

Basically, you have to create a stream, with the right options (there is a full list on that page), and use it as the third parameter to file_get_contents -- nothing more ;-)

As a sidenote : generally speaking, to send HTTP POST requests, we tend to use curl, which provides a lot of options an all -- but streams are one of the nice things of PHP that nobody knows about... too bad...

Best Regular Expression for Email Validation in C#

First option (bad because of throw-catch, but MS will do work for you):

bool IsValidEmail(string email)
    try {
        var mail = new System.Net.Mail.MailAddress(email);
        return true;
    catch {
        return false;

Second option is read I Knew How To Validate An Email Address Until I Read The RFC and RFC specification

Android get current Locale, not default

As per official documentation ConfigurationCompat is deprecated in support libraries

You can consider using

LocaleListCompat.getDefault()[0].toLanguageTag() 0th position will be user preferred locale

To get Default locale at 0th position would be LocaleListCompat.getAdjustedDefault()

Converting a double to an int in C#

In the provided example your decimal is 8.6. Had it been 8.5 or 9.5, the statement i1 == i2 might have been true. Infact it would have been true for 8.5, and false for 9.5.


Regardless of the decimal part, the second statement, int i2 = (int)score will discard the decimal part and simply return you the integer part. Quite dangerous thing to do, as data loss might occur.

Now, for the first statement, two things can happen. If the decimal part is 5, that is, it is half way through, a decision is to be made. Do we round up or down? In C#, the Convert class implements banker's rounding. See this answer for deeper explanation. Simply put, if the number is even, round down, if the number is odd, round up.

E.g. Consider:

        double score = 8.5;
        int i1 = Convert.ToInt32(score); // 8
        int i2 = (int)score;             // 8

        score += 1;
        i1 = Convert.ToInt32(score);     // 10
        i2 = (int)score;                 // 9

Converting a view to Bitmap without displaying it in Android?

Hope this helps

View view="some view instance";        
Bitmap bitmap=view.getDrawingCache();

getDrawingCache() method is deprecated in API level 28. So look for other alternative for API level > 28.

Why do I have to "git push --set-upstream origin <branch>"?

TL;DR: git branch --set-upstream-to origin/solaris

The answer to the question you asked—which I'll rephrase a bit as "do I have to set an upstream"—is: no, you don't have to set an upstream at all.

If you do not have upstream for the current branch, however, Git changes its behavior on git push, and on other commands as well.

The complete push story here is long and boring and goes back in history to before Git version 1.5. To shorten it a whole lot, git push was implemented poorly.1 As of Git version 2.0, Git now has a configuration knob spelled push.default which now defaults to simple. For several versions of Git before and after 2.0, every time you ran git push, Git would spew lots of noise trying to convince you to set push.default just to get git push to shut up.

You do not mention which version of Git you are running, nor whether you have configured push.default, so we must guess. My guess is that you are using Git version 2-point-something, and that you have set push.default to simple to get it to shut up. Precisely which version of Git you have, and what if anything you have push.default set to, does matter, due to that long and boring history, but in the end, the fact that you're getting yet another complaint from Git indicates that your Git is configured to avoid one of the mistakes from the past.

What is an upstream?

An upstream is simply another branch name, usually a remote-tracking branch, associated with a (regular, local) branch.

Every branch has the option of having one (1) upstream set. That is, every branch either has an upstream, or does not have an upstream. No branch can have more than one upstream.

The upstream should, but does not have to be, a valid branch (whether remote-tracking like origin/B or local like master). That is, if the current branch B has upstream U, git rev-parse U should work. If it does not work—if it complains that U does not exist—then most of Git acts as though the upstream is not set at all. A few commands, like git branch -vv, will show the upstream setting but mark it as "gone".

What good is an upstream?

If your push.default is set to simple or upstream, the upstream setting will make git push, used with no additional arguments, just work.

That's it—that's all it does for git push. But that's fairly significant, since git push is one of the places where a simple typo causes major headaches.

If your push.default is set to nothing, matching, or current, setting an upstream does nothing at all for git push.

(All of this assumes your Git version is at least 2.0.)

The upstream affects git fetch

If you run git fetch with no additional arguments, Git figures out which remote to fetch from by consulting the current branch's upstream. If the upstream is a remote-tracking branch, Git fetches from that remote. (If the upstream is not set or is a local branch, Git tries fetching origin.)

The upstream affects git merge and git rebase too

If you run git merge or git rebase with no additional arguments, Git uses the current branch's upstream. So it shortens the use of these two commands.

The upstream affects git pull

You should never2 use git pull anyway, but if you do, git pull uses the upstream setting to figure out which remote to fetch from, and then which branch to merge or rebase with. That is, git pull does the same thing as git fetch—because it actually runs git fetch—and then does the same thing as git merge or git rebase, because it actually runs git merge or git rebase.

(You should usually just do these two steps manually, at least until you know Git well enough that when either step fails, which they will eventually, you recognize what went wrong and know what to do about it.)

The upstream affects git status

This may actually be the most important. Once you have an upstream set, git status can report the difference between your current branch and its upstream, in terms of commits.

If, as is the normal case, you are on branch B with its upstream set to origin/B, and you run git status, you will immediately see whether you have commits you can push, and/or commits you can merge or rebase onto.

This is because git status runs:

  • git rev-list --count @{u}..HEAD: how many commits do you have on B that are not on origin/B?
  • git rev-list --count HEAD..@{u}: how many commits do you have on origin/B that are not on B?

Setting an upstream gives you all of these things.

How come master already has an upstream set?

When you first clone from some remote, using:

$ git clone git://

or similar, the last step Git does is, essentially, git checkout master. This checks out your local branch master—only you don't have a local branch master.

On the other hand, you do have a remote-tracking branch named origin/master, because you just cloned it.

Git guesses that you must have meant: "make me a new local master that points to the same commit as remote-tracking origin/master, and, while you're at it, set the upstream for master to origin/master."

This happens for every branch you git checkout that you do not already have. Git creates the branch and makes it "track" (have as an upstream) the corresponding remote-tracking branch.

But this doesn't work for new branches, i.e., branches with no remote-tracking branch yet.

If you create a new branch:

$ git checkout -b solaris

there is, as yet, no origin/solaris. Your local solaris cannot track remote-tracking branch origin/solaris because it does not exist.

When you first push the new branch:

$ git push origin solaris

that creates solaris on origin, and hence also creates origin/solaris in your own Git repository. But it's too late: you already have a local solaris that has no upstream.3

Shouldn't Git just set that, now, as the upstream automatically?

Probably. See "implemented poorly" and footnote 1. It's hard to change now: There are millions4 of scripts that use Git and some may well depend on its current behavior. Changing the behavior requires a new major release, nag-ware to force you to set some configuration field, and so on. In short, Git is a victim of its own success: whatever mistakes it has in it, today, can only be fixed if the change is either mostly invisible, clearly-much-better, or done slowly over time.

The fact is, it doesn't today, unless you use --set-upstream or -u during the git push. That's what the message is telling you.

You don't have to do it like that. Well, as we noted above, you don't have to do it at all, but let's say you want an upstream. You have already created branch solaris on origin, through an earlier push, and as your git branch output shows, you already have origin/solaris in your local repository.

You just don't have it set as the upstream for solaris.

To set it now, rather than during the first push, use git branch --set-upstream-to. The --set-upstream-to sub-command takes the name of any existing branch, such as origin/solaris, and sets the current branch's upstream to that other branch.

That's it—that's all it does—but it has all those implications noted above. It means you can just run git fetch, then look around, then run git merge or git rebase as appropriate, then make new commits and run git push, without a bunch of additional fussing-around.

1To be fair, it was not clear back then that the initial implementation was error-prone. That only became clear when every new user made the same mistakes every time. It's now "less poor", which is not to say "great".

2"Never" is a bit strong, but I find that Git newbies understand things a lot better when I separate out the steps, especially when I can show them what git fetch actually did, and they can then see what git merge or git rebase will do next.

3If you run your first git push as git push -u origin solaris—i.e., if you add the -u flag—Git will set origin/solaris as the upstream for your current branch if (and only if) the push succeeds. So you should supply -u on the first push. In fact, you can supply it on any later push, and it will set or change the upstream at that point. But I think git branch --set-upstream-to is easier, if you forgot.

4Measured by the Austin Powers / Dr Evil method of simply saying "one MILLLL-YUN", anyway.

add string to String array

First, this code here,

string [] scripts = new String [] ("test3","test4","test5");

should be

String[] scripts = new String [] {"test3","test4","test5"};

Please read this tutorial on Arrays


Arrays are fixed size, so you can't add new Strings to above array. You may override existing values

scripts[0] = string1;


Create array with size then keep on adding elements till it is full.

If you want resizable arrays, consider using ArrayList.

How to know elastic search installed version from kibana?

If you are logged into your Kibana, you can click on the Management tab and that will show your Kibana version. Alternatively, you can click on the small tube-like icon enter image description here and that will show the version number.

How to print values separated by spaces instead of new lines in Python 2.7

This does almost everything you want:

f = open('data.txt', 'rb')

while True:
    char =
    if not char: break
    print "{:02x}".format(ord(char)),

With data.txt created like this:

f = open('data.txt', 'wb')

I get the following output:

61 62 0d 0a 63 64

tl;dr -- 1. You are using poor variable names. 2. You are slicing your hex strings incorrectly. 3. Your code is never going to replace any newlines. You may just want to forget about that feature. You do not quite yet understand the difference between a character, its integer code, and the hex string that represents the integer. They are all different: two are strings and one is an integer, and none of them are equal to each other. 4. For some files, you shouldn't remove newlines.


1. Your variable names are horrendous.

That's fine if you never want to ask anybody questions. But since every one needs to ask questions, you need to use descriptive variable names that anyone can understand. Your variable names are only slightly better than these:

fname = 'data.txt'
f = open(fname, 'rb')
xxxyxx =

xxyxxx = len(xxxyxx)
print "Length of file is", xxyxxx, "bytes. "
yxxxxx = 0

while yxxxxx < xxyxxx:
    xyxxxx = hex(ord(xxxyxx[yxxxxx]))
    xyxxxx = xyxxxx[-2:]
    yxxxxx = yxxxxx + 1
    xxxxxy = chr(13) + chr(10)
    xxxxyx = str(xxxxxy)
    xyxxxxx = str(xyxxxx)
    xyxxxxx.replace(xxxxyx, ' ')
    print xyxxxxx

That program runs fine, but it is impossible to understand.

2. The hex() function produces strings of different lengths.

For instance,

print hex(61)
print hex(15)


And taking the slice [-2:] for each of those strings gives you:


See how you got the 'x' in the second one? The slice:


says to go to the end of the string and back up two characters, then grab the rest of the string. Instead of doing that, take the slice starting 3 characters in from the beginning:


3. Your code will never replace any newlines.

Suppose your file has these two consecutive characters:


Now you read in the first character, "\r", and convert it to an integer, ord("\r"), giving you the integer 13. Now you convert that to a string, hex(13), which gives you the string "0xd", and you slice off the first two characters giving you:


Next, this line in your code:

bndtx.replace(entx, ' ')

tries to find every occurrence of the string "\r\n" in the string "d" and replace it. There is never going to be any replacement because the replacement string is two characters long and the string "d" is one character long.

The replacement won't work for "\r\n" and "0d" either. But at least now there is a possibility it could work because both strings have two characters. Let's reduce both strings to a common denominator: ascii codes. The ascii code for "\r" is 13, and the ascii code for "\n" is 10. Now what about the string "0d"? The ascii code for the character "0" is 48, and the ascii code for the character "d" is 100. Those strings do not have a single character in common. Even this doesn't work:

 x = '0d' + '0a'
 x.replace("\r\n", " ")
 print x


Nor will this:

x = 'd' + 'a'
x.replace("\r\n", " ")
print x


The bottom line is: converting a character to an integer then to a hex string does not end up giving you the original character--they are just different strings. So if you do this:

char = "a"
code = ord(char)
hex_str = hex(code)

print char.replace(hex_str, " ") can't expect "a" to be replaced by a space. If you examine the output here:

char = "a"
print repr(char)

code = ord(char)
print repr(code)

hex_str = hex(code)
print repr(hex_str)

print repr(
    char.replace(hex_str, " ")


You can see that 'a' is a string with one character in it, and '0x61' is a string with 4 characters in it: '0', 'x', '6', and '1', and you can never find a four character string inside a one character string.

4) Removing newlines can corrupt the data.

For some files, you do not want to replace newlines. For instance, if you were reading in a .jpg file, which is a file that contains a bunch of integers representing colors in an image, and some colors in the image happened to be represented by the number 13 followed by the number 10, your code would eliminate those colors from the output.

However, if you are writing a program to read only text files, then replacing newlines is fine. But then, different operating systems use different newlines. You are trying to replace Windows newlines(\r\n), which means your program won't work on files created by a Mac or Linux computer, which use \n for newlines. There are easy ways to solve that, but maybe you don't want to worry about that just yet.

I hope all that's not too confusing.

Static Vs. Dynamic Binding in Java

All answers here are correct but i want to add something which is missing. when you are overriding a static method, it looks like we are overriding it but actually it is not method overriding. Instead it is called method hiding. Static methods cannot be overridden in Java.

Look at below example:

class Animal {
    static void eat() {
        System.out.println("animal is eating...");

class Dog extends Animal {

    public static void main(String args[]) {

        Animal a = new Dog();; // prints >> animal is eating...


    static void eat() {
        System.out.println("dog is eating...");

In dynamic binding, method is called depending on the type of reference and not the type of object that the reference variable is holding Here static bindinghappens because method hiding is not a dynamic polymorphism. If you remove static keyword in front of eat() and make it a non static method then it will show you dynamic polymorphism and not method-hiding.

i found the below link to support my answer:

The SQL OVER() clause - when and why is it useful?

You can use GROUP BY SalesOrderID. The difference is, with GROUP BY you can only have the aggregated values for the columns that are not included in GROUP BY.

In contrast, using windowed aggregate functions instead of GROUP BY, you can retrieve both aggregated and non-aggregated values. That is, although you are not doing that in your example query, you could retrieve both individual OrderQty values and their sums, counts, averages etc. over groups of same SalesOrderIDs.

Here's a practical example of why windowed aggregates are great. Suppose you need to calculate what percent of a total every value is. Without windowed aggregates you'd have to first derive a list of aggregated values and then join it back to the original rowset, i.e. like this:

  orig.Value * 100.0 / agg.TotalValue AS ValuePercent
FROM OriginalRowset orig
      SUM(Value) AS TotalValue
    FROM OriginalRowset
    GROUP BY [Partition]
  ) agg ON orig.[Partition] = agg.[Partition]

Now look how you can do the same with a windowed aggregate:

  Value * 100.0 / SUM(Value) OVER (PARTITION BY [Partition]) AS ValuePercent
FROM OriginalRowset orig

Much easier and cleaner, isn't it?

How to disable/enable select field using jQuery?

Your select doesn't have an ID, only a name. You'll need to modify your selector:

$("#pizza").on("click", function(){
  $("select[name='pizza_kind']").prop("disabled", !this.checked);


Merge two HTML table cells

Set the colspan attribute to 2.

...but please don't use tables for layout.

Angular2: How to load data before rendering the component?

You can pre-fetch your data by using Resolvers in Angular2+, Resolvers process your data before your Component fully be loaded.

There are many cases that you want to load your component only if there is certain thing happening, for example navigate to Dashboard only if the person already logged in, in this case Resolvers are so handy.

Look at the simple diagram I created for you for one of the way you can use the resolver to send the data to your component.

enter image description here

Applying Resolver to your code is pretty simple, I created the snippets for you to see how the Resolver can be created:

import { Injectable } from '@angular/core';
import { Router, Resolve, RouterStateSnapshot, ActivatedRouteSnapshot } from '@angular/router';
import { MyData, MyService } from './my.service';

export class MyResolver implements Resolve<MyData> {
  constructor(private ms: MyService, private router: Router) {}

  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Promise<MyData> {
    let id = route.params['id'];

    return => {
      if (data) {
        return data;
      } else {

and in the module:

import { MyResolver } from './my-resolver.service';

  imports: [
  exports: [
  providers: [
export class MyModule { }

and you can access it in your Component like this:

 ngOnInit() {
      .subscribe((data: { mydata: myData }) => { =;

And in the Route something like this (usually in the app.routing.ts file):

{path: 'yourpath/:id', component: YourComponent, resolve: { myData: MyResolver}}

Laravel - Session store not set on request

A problem can be that you try to access you session inside of your controller's __constructor() function.

From Laravel 5.3+ this is not possible anymore because it is not intended to work anyway, as stated in the upgrade guide.

In previous versions of Laravel, you could access session variables or the authenticated user in your controller's constructor. This was never intended to be an explicit feature of the framework. In Laravel 5.3, you can't access the session or authenticated user in your controller's constructor because the middleware has not run yet.

For more background information also read Taylor his response.


If you still want to use this, you can dynamically create a middleware and run it in the constructor, as described in the upgrade guide:

As an alternative, you may define a Closure based middleware directly in your controller's constructor. Before using this feature, make sure that your application is running Laravel 5.3.4 or above:


namespace App\Http\Controllers;

use App\User;
use Illuminate\Support\Facades\Auth;
use App\Http\Controllers\Controller;

class ProjectController extends Controller
     * All of the current user's projects.
    protected $projects;

     * Create a new controller instance.
     * @return void
    public function __construct()
        $this->middleware(function ($request, $next) {
            $this->projects = Auth::user()->projects;

            return $next($request);

How to get a vCard (.vcf file) into Android contacts from website

I had problems with importing a VERSION:4.0 vcard file on Android 7 (LineageOS) with the standard Contacts app.

Since this is on the top search hits for "android vcard format not supported", I just wanted to note that I was able to import them with the Simple Contacts app (Play or F-Droid).

Getting strings recognized as variable names in R

If you want to use a string as a variable name, you can use assign:


assign(var1, c(5,4,5,6,7))


[1] 5 4 5 6 7

What is the purpose of the : (colon) GNU Bash builtin?

I use it to easily enable/disable variable commands:

if [[ "$VERBOSE" == "" || "$VERBOSE" == "0" ]]; then
    vecho=":"     # no "verbose echo"
    vecho=echo    # enable "verbose echo"

$vecho "Verbose echo is ON"


$ ./vecho
$ VERBOSE=1 ./vecho
Verbose echo is ON

This makes for a clean script. This cannot be done with '#'.


: >afile

is one of the simplest ways to guarantee that 'afile' exists but is 0 length.

Angular 2: How to call a function after get a response from subscribe

You can add a callback function to your list of get_category(...) parameters.


 get_categories(number, callback){ url, body, {headers: headers, withCredentials:true})
      response => { = response.json();

      }, error => {


And then you can just call get_category(...) like this:

this.get_category(1, name_of_function);

How can I remove the top and right axis in matplotlib?

Alternatively, this

def simpleaxis(ax):

seems to achieve the same effect on an axis without losing rotated label support.

(Matplotlib 1.0.1; solution inspired by this).

How to go from one page to another page using javascript?

You cannot sanely depend on client side JavaScript to determine if user credentials are correct. The browser (and all code that executes that) is under the control of the user, not you, so it is not trustworthy.

The username and password need to be entered using a form. The OK button will be a submit button. The action attribute must point to a URL which will be handled by a program that checks the credentials.

This program could be written in JavaScript, but how you go about that would depend on which server side JavaScript engine you were using. Note that SSJS is not a mainstream technology so if you really want to use it, you would have to use specialised hosting or admin your own server.

(Half a decade later and SSJS is much more common thanks to Node.js, it is still fairly specialised though).

If you want to redirect afterwards, then the program needs to emit an HTTP Location header.

Note that you need to check the credentials are OK (usually by storing a token, which isn't the actual password, in a cookie) before outputting any private page. Otherwise anyone could get to the private pages by knowing the URL (and thus bypassing the login system).

How do the post increment (i++) and pre increment (++i) operators work in Java?

++a is prefix increment operator:

  • the result is calculated and stored first,
  • then the variable is used.

a++ is postfix increment operator:

  • the variable is used first,
  • then the result is calculated and stored.

Once you remember the rules, EZ for ya to calculate everything!

jQuery: value.attr is not a function

You can also use jQuery('.class-name').attr("href"), in my case it works better.

Here more information: "jQuery(...)" instead of "$(...)"

create table in postgreSQL

Replace bigint(20) not null auto_increment by bigserial not null and datetime by timestamp

R color scatter plot points based on values

It's better to create a new factor variable using cut(). I've added a few options using ggplot2 also.

df <- data.frame(
  X1=seq(0, 5, by=0.001),
  X2=rnorm(df$X1, mean = 3.5, sd = 1.5)

# Create new variable for plotting
df$Colour <- cut(df$X2, breaks = c(-Inf, 1, 3, +Inf), 
                 labels = c("low", "medium", "high"), 
                 right = FALSE)

### Base Graphics

plot(df$X1, df$X2, 
     col = df$Colour, ylim = c(0, 10), xlab = "POS", 
     ylab = "CS", main = "Plot Title", pch = 21)

     col = df$Colour, ylim = c(0, 10), xlab = "POS", 
     ylab = "CS", main = "Plot Title", pch = 19, cex = 0.5)

# Using `with()` 

     plot(X1, X2, xlab="POS", ylab="CS", col = Colour, pch=21, cex=1.4)

# Using ggplot2

# qplot()
qplot(df$X1, df$X2, colour = df$Colour)

# ggplot()
p <- ggplot(df, aes(X1, X2, colour = Colour)) 
p <- p + geom_point() + xlab("POS") + ylab("CS")

p + facet_grid(Colour~., scales = "free")

Find indices of elements equal to zero in a NumPy array

If you are working with a one-dimensional array there is a syntactic sugar:

>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.flatnonzero(x == 0)
array([1, 3, 5])

Android LinearLayout Gradient Background

With Kotlin you can do that in just 2 lines

Change color values in the array

                  val gradientDrawable = GradientDrawable(
                    gradientDrawable.cornerRadius = 0f;

                   //Set Gradient


enter image description here

Correct way to integrate jQuery plugins in AngularJS

Yes, you are correct. If you are using a jQuery plugin, do not put the code in the controller. Instead create a directive and put the code that you would normally have inside the link function of the directive.

There are a couple of points in the documentation that you could take a look at. You can find them here:
Common Pitfalls

Using controllers correctly

Ensure that when you are referencing the script in your view, you refer it last - after the angularjs library, controllers, services and filters are referenced.

EDIT: Rather than using $(element), you can make use of angular.element(element) when using AngularJS with jQuery

Changing Tint / Background color of UITabBar

There is no simple way to do this, you basically need to subclass UITabBar and implement custom drawing to do what you want. It is quite a bit of work for the effect, but it may be worth it. I recommend filing a bug with Apple to get it added to a future iPhone SDK.

android.content.res.Resources$NotFoundException: String resource ID #0x0

You can do it. this is a easy way.


A formula to copy the values from a formula to another column

Copy the cell. Paste special as link. Will update with original. No formula though.

Gradient borders

It's a hack, but you can achieve this effect in some cases by using the background-image to specify the gradient and then masking the actual background with a box-shadow. For example:

p {
  display: inline-block;
  width: 50px;
  height: 50px;
  /* The background is used to specify the border background */
  background: -moz-linear-gradient(45deg, #f00, #ff0);
  background: -webkit-linear-gradient(45deg, #f00, #ff0);
  /* Background origin is the padding box by default.
  Override to make the background cover the border as well. */
  -moz-background-origin: border;
  background-origin: border-box;
  /* A transparent border determines the width */
  border: 4px solid transparent;
  border-radius: 8px;
    inset 0 0 12px #0cc, /* Inset shadow */
    0 0 12px #0cc, /* Outset shadow */
    inset -999px 0 0 #fff; /* The background color */


jQuery - Detecting if a file has been selected in the file input

I'd suggest try the change event? test to see if it has a value if it does then you can continue with your code. jQuery has

.bind("change", function(){ ... });


.change(function(){ ... }); 

which are equivalents.

for a unique selector change your name attribute to id and then jQuery("#imafile") or a general jQuery('input[type="file"]') for all the file inputs

Web link to specific whatsapp contact

The following link seems to work fine -

<a href="whatsapp://send?text=Hello World!&phone=+9198********1">Ping me on WhatsApp</a>

It opens the contact in WhatsApp app, along with the message 'Hello World!' prepopulated in the input text box.

(Tested this with google chrome on an android phone.)

How to read barcodes with the camera on Android?

2016 update

With the latest release of Google Play Services, v7.8, you have access to the new Mobile Vision API. That's probably the most convenient way to implement barcode scanning now, and it also works offline.

From the Android Barcode API:

The Barcode API detects barcodes in real-time, on device, in any orientation. It can also detect multiple barcodes at once.

It reads the following barcode formats:

  • 1D barcodes: EAN-13, EAN-8, UPC-A, UPC-E, Code-39, Code-93, Code-128, ITF, Codabar
  • 2D barcodes: QR Code, Data Matrix, PDF-417, AZTEC

It automatically parses QR Codes, Data Matrix, PDF-417, and Aztec values, for the following supported formats:

  • URL
  • Contact information (VCARD, etc.)
  • Calendar event
  • Email
  • Phone
  • SMS
  • ISBN
  • WiFi
  • Geo-location (latitude and longitude)
  • AAMVA driver license/ID

PuTTY scripting to log onto host

For me it works this way:

putty -ssh [email protected] 22 -pw password

putty, protocol, user name @ ip address port and password. To connect in less than a second.

How to Find Item in Dictionary Collection?

Of course, if you want to make sure it's in there otherwise fail then this works:

thisTag = _tags[key];

NOTE: This will fail if the key,value pair does not exists but sometimes that is exactly what you want. This way you can catch it and do something about the error. I would only do this if I am certain that the key,value pair is or should be in the dictionary and if not I want it to know about it via the throw.

How do I use $scope.$watch and $scope.$apply in AngularJS?

There are $watchGroup and $watchCollection as well. Specifically, $watchGroup is really helpful if you want to call a function to update an object which has multiple properties in a view that is not dom object, for e.g. another view in canvas, WebGL or server request.

Here, the documentation link.

Conditional statement in a one line lambda function in python?

In case you want to be lazier:

#syntax lambda x : (false,true)[Condition]

In your case:

rate = lambda(T) : (400*exp(-T),200*exp(-T))[T>200]

Find Item in ObservableCollection without using a loop

I Don't know what do you mean exactly, but technially speaking, this is not possible without a loop.

May be you mean using a LINQ, like for example:

list.Where(x=>x.Title == title)

It's worth mentioning that the iteration over is not skipped, but simply wrapped into the LINQ query.

Hope this helps.


In other words if you really concerned about performance, keep coding the way you already doing. Otherwise choose LINQ for more concise and clear syntax.

How to get rid of punctuation using NLTK tokenizer?

You do not really need NLTK to remove punctuation. You can remove it with simple python. For strings:

import string
s = '... some string with punctuation ...'
s = s.translate(None, string.punctuation)

Or for unicode:

import string
translate_table = dict((ord(char), None) for char in string.punctuation)   

and then use this string in your tokenizer.

P.S. string module have some other sets of elements that can be removed (like digits).

How do I copy directories recursively with gulp?

Turns out that to copy a complete directory structure gulp needs to be provided with a base for your gulp.src() method.

So gulp.src( [ files ], { "base" : "." }) can be used in the structure above to copy all the directories recursively.

If, like me, you may forget this then try:

    return gulp.src(src, {base:"."})

Django datetime issues (

Instead of using you should be really using from django.utils.timezone import now


so go for something like this:

from django.utils.timezone import now

created_date = models.DateTimeField(default=now, editable=False)

What is the correct target for the JAVA_HOME environment variable for a Linux OpenJDK Debian-based distribution?

As an update for fedora user , alternatives set current java directory to /usr/java/default

so you have to set your JAVA_HOME to /usr/java/default to always have alternatives curent selection in your classpath


Get User Selected Range

You can loop through the Selection object to see what was selected. Here is a code snippet from Microsoft (

Sub Count_Selection()
    Dim cell As Object
    Dim count As Integer
    count = 0
    For Each cell In Selection
        count = count + 1
    Next cell
    MsgBox count & " item(s) selected"
End Sub

WARNING in budgets, maximum exceeded for initial

Open angular.json file and find budgets keyword.

It should look like:

    "budgets": [
          "type": "initial",
          "maximumWarning": "2mb",
          "maximumError": "5mb"

As you’ve probably guessed you can increase the maximumWarning value to prevent this warning, i.e.:

    "budgets": [
          "type": "initial",
          "maximumWarning": "4mb", <===
          "maximumError": "5mb"

What does budgets mean?

A performance budget is a group of limits to certain values that affect site performance, that may not be exceeded in the design and development of any web project.

In our case budget is the limit for bundle sizes.

See also:

How to sort by two fields in Java?

Arrays.sort(persons, new PersonComparator());

import java.util.Comparator;

public class PersonComparator implements Comparator<? extends Person> {

    public int compare(Person o1, Person o2) {
        if(null == o1 || null == o2  || null == o1.getName() || null== o2.getName() ){
            throw new NullPointerException();
            int nameComparisonResult = o1.getName().compareTo(o2.getName());
            if(0 == nameComparisonResult){
                return o1.getAge()-o2.getAge();
                return nameComparisonResult;

class Person{
    int age; String name;

    public int getAge() {
        return age;

    public void setAge(int age) {
        this.age = age;

    public String getName() {
        return name;

    public void setName(String name) { = name;


Updated version:

public class PersonComparator implements Comparator<? extends Person> {

   public int compare(Person o1, Person o2) {

      int nameComparisonResult = o1.getName().compareToIgnoreCase(o2.getName());
      return 0 == nameComparisonResult?o1.getAge()-o2.getAge():nameComparisonResult;


How to get dictionary values as a generic list

My OneLiner:

var MyList = new List<MyType>(MyDico.Values);

Is there a way to specify how many characters of a string to print out using printf()?

Using printf you can do

printf("Here are the first 8 chars: %.8s\n", "A string that is more than 8 chars");

If you're using C++, you can achieve the same result using the STL:

using namespace std; // for clarity
string s("A string that is more than 8 chars");
cout << "Here are the first 8 chars: ";
copy(s.begin(), s.begin() + 8, ostream_iterator<char>(cout));
cout << endl;

Or, less efficiently:

cout << "Here are the first 8 chars: " <<
        string(s.begin(), s.begin() + 8) << endl;

Box shadow for bottom side only

Specify negative value to spread value. This works for me:

box-shadow: 0 2px 3px -1px rgba(0, 0, 0, 0.1);

Jquery $.ajax fails in IE on cross domain calls

Note, adding

$.support.cors = true;

was sufficient to force $.ajax calls to work on IE8

scrollTop jquery, scrolling to div with id?

try this

    $('#div_id').animate({scrollTop:0}, '500', 'swing');

Web-scraping JavaScript page with Python

It sounds like the data you're really looking for can be accessed via secondary URL called by some javascript on the primary page.

While you could try running javascript on the server to handle this, a simpler approach to might be to load up the page using Firefox and use a tool like Charles or Firebug to identify exactly what that secondary URL is. Then you can just query that URL directly for the data you are interested in.

Check if a class is derived from a generic class

late to the game on this... i too have yet another permutation of JarodPar's answer.

here's Type.IsSubClassOf(Type) courtesy of reflector:

    public virtual bool IsSubclassOf(Type c)
        Type baseType = this;
        if (!(baseType == c))
            while (baseType != null)
                if (baseType == c)
                    return true;
                baseType = baseType.BaseType;
            return false;
        return false;

from that, we see that it's not doing anything too cray cray and is similar to JaredPar's iterative approach. so far, so good. here's my version (disclaimer: not thoroughly tested, so lemme know if you find issues)

    public static bool IsExtension(this Type thisType, Type potentialSuperType)
        // protect ya neck
        if (thisType == null || potentialSuperType == null || thisType == potentialSuperType) return false;

        // don't need to traverse inheritance for interface extension, so check/do these first
        if (potentialSuperType.IsInterface)
            foreach (var interfaceType in thisType.GetInterfaces())
                var tempType = interfaceType.IsGenericType ? interfaceType.GetGenericTypeDefinition() : interfaceType;

                if (tempType == potentialSuperType)
                    return true;

        // do the concrete type checks, iterating up the inheritance chain, as in orignal
        while (thisType != null && thisType != typeof(object))
            var cur = thisType.IsGenericType ? thisType.GetGenericTypeDefinition() : thisType;

            if (potentialSuperType == cur)
                return true;

            thisType = thisType.BaseType;
        return false;

basically this is just an extension method to System.Type - i did this to intentionally limit the "thisType" Type to concrete Types, as my immediate usage is to LINQ query "where" predicates against Type objects. i'm sure all you smart folks out there could bang it down to an efficient, all-purpose static method if you need to :) the code does a few things the answer's code doesn't

  1. open's it up to to general "extension" - i'm considering inheritance (think classes) as well as implementation (interfaces); method and parameter names are changed to better reflect this
  2. input null-validation (meah)
  3. input of same type (a class cannot extend itself)
  4. short-circuit execution if Type in question is an interface; because GetInterfaces() returns all implemented interfaces (even ones implemented in super-classes), you can simply loop through that collection not having to climb the inheritance tree

the rest is basically the same as JaredPar's code

Terminating idle mysql connections

Manual cleanup:

You can KILL the processid.

mysql> show full processlist;
| Id      | User       | Host              | db   | Command | Time  | State | Info                  |
| 1193777 | TestUser12 | | www  | Sleep   | 25946 |       | NULL                  |

mysql> kill 1193777;


  • the php application might report errors (or the webserver, check the error logs)
  • don't fix what is not broken - if you're not short on connections, just leave them be.

Automatic cleaner service ;)

Or you configure your mysql-server by setting a shorter timeout on wait_timeout and interactive_timeout

mysql> show variables like "%timeout%";
| Variable_name            | Value |
| connect_timeout          | 5     |
| delayed_insert_timeout   | 300   |
| innodb_lock_wait_timeout | 50    |
| interactive_timeout      | 28800 |
| net_read_timeout         | 30    |
| net_write_timeout        | 60    |
| slave_net_timeout        | 3600  |
| table_lock_wait_timeout  | 50    |
| wait_timeout             | 28800 |
9 rows in set (0.00 sec)

Set with:

set global wait_timeout=3;
set global interactive_timeout=3;

(and also set in your configuration file, for when your server restarts)

But you're treating the symptoms instead of the underlying cause - why are the connections open? If the PHP script finished, shouldn't they close? Make sure your webserver is not using connection pooling...

To switch from vertical split to horizontal split fast in Vim

In VIM, take a look at the following to see different alternatives for what you might have done:

:help opening-window

For instance:

Ctrl-W s
Ctrl-W o
Ctrl-W v
Ctrl-W o
Ctrl-W s

PIL image to array (numpy array to array) - Python

Based on zenpoy's answer:

import Image
import numpy

def image2pixelarray(filepath):
    filepath : str
        Path to an image file

        A list of lists which make it simple to access the greyscale value by
    im ='L')
    (width, height) = im.size
    greyscale_map = list(im.getdata())
    greyscale_map = numpy.array(greyscale_map)
    greyscale_map = greyscale_map.reshape((height, width))
    return greyscale_map

Keeping session alive with Curl and PHP

You also need to set the option CURLOPT_COOKIEFILE.

The manual describes this as

The name of the file containing the cookie data. The cookie file can be in Netscape format, or just plain HTTP-style headers dumped into a file. If the name is an empty string, no cookies are loaded, but cookie handling is still enabled.

Since you are using the cookie jar you end up saving the cookies when the requests finish, but since the CURLOPT_COOKIEFILE is not given, cURL isn't sending any of the saved cookies on subsequent requests.

How to get IP address of running docker container

If you don't want to map ports from your host to the container you can access directly to the docker range ip for the container. This range is by default only accessed from your host. You can check your container network data doing:

docker inspect <containerNameOrId>

Probably is better to filter:

docker inspect <containerNameOrId> | grep '"IPAddress"' | head -n 1

Usually, the default docker ip range is Your host should be and your first container should be if everything is normal and you didn't specify any special network options.

EDIT Another more elegant way using docker features instead of "bash tricking":

docker inspect -f "{{ .NetworkSettings.IPAddress }}" <containerNameOrId>

Best way to incorporate Volley (or other library) into Android Studio project


compile ''

OLD ANSWER: You need the next in your build.gradle of your app module:

dependencies {
        compile 'com.mcxiaoke.volley:library:1.0.19'
        (Rest of your dependencies)


This is not the official repo but is a highly trusted one.

Controlling Spacing Between Table Cells

Use border-collapse and border-spacing to get spaces between the table cells. I would not recommend using floating cells as suggested by QQping.


Random / noise functions for GLSL

Please see below an example how to add white noise to the rendered texture. The solution is to use two textures: original and pure white noise, like this one: wiki white noise

private static final String VERTEX_SHADER =
    "uniform mat4 uMVPMatrix;\n" +
    "uniform mat4 uMVMatrix;\n" +
    "uniform mat4 uSTMatrix;\n" +
    "attribute vec4 aPosition;\n" +
    "attribute vec4 aTextureCoord;\n" +
    "varying vec2 vTextureCoord;\n" +
    "varying vec4 vInCamPosition;\n" +
    "void main() {\n" +
    "    vTextureCoord = (uSTMatrix * aTextureCoord).xy;\n" +
    "    gl_Position = uMVPMatrix * aPosition;\n" +

private static final String FRAGMENT_SHADER =
        "precision mediump float;\n" +
        "uniform sampler2D sTextureUnit;\n" +
        "uniform sampler2D sNoiseTextureUnit;\n" +
        "uniform float uNoseFactor;\n" +
        "varying vec2 vTextureCoord;\n" +
        "varying vec4 vInCamPosition;\n" +
        "void main() {\n" +
                "    gl_FragColor = texture2D(sTextureUnit, vTextureCoord);\n" +
                "    vec4 vRandChosenColor = texture2D(sNoiseTextureUnit, fract(vTextureCoord + uNoseFactor));\n" +
                "    gl_FragColor.r += (0.05 * vRandChosenColor.r);\n" +
                "    gl_FragColor.g += (0.05 * vRandChosenColor.g);\n" +
                "    gl_FragColor.b += (0.05 * vRandChosenColor.b);\n" +

The fragment shared contains parameter uNoiseFactor which is updated on every rendering by main application:

float noiseValue = (float)(mRand.nextInt() % 1000)/1000;
int noiseFactorUniformHandle = GLES20.glGetUniformLocation( mProgram, "sNoiseTextureUnit");
GLES20.glUniform1f(noiseFactorUniformHandle, noiseFactor);

How do I download a file from the internet to my linux server with Bash

Using wget

wget -O /tmp/myfile ''

or curl:

curl -o /tmp/myfile ''

Python 2.7.10 error "from urllib.request import urlopen" no module named request

Try using urllib2:

This line should work to replace urlopen:

from urllib2 import urlopen

Tested in Python 2.7 on Macbook Pro

Try posting a link to the git in question.

How can I find my php.ini on wordpress?

I just came across this thread while searching for an answer to why the php.ini file would be within the /wp-admin/ folder for WordPress that I have just seen in an odd setup - because it really really shouldn't be there.

WordPress by default doesn't include a php.ini file within the /wp-admin/ folder, so you should not have one there yourself. The php.ini file is designed to override the main server PHP configuration settings so that your account on the server is treated differently, within limits. As such, if you do need to use this file, please, for your own sanity (and that of others who happen to work with your systems in the future...), place the php.ini file in the root of your account, not hidden away in the /wp-admin/ folder, or any other folder for that matter.

I'm surprised to see so many others commenting that it should be in the /wp-admin/ folder to be honest. I'd love to see some official documentation from WordPress stating that this is best practice, as this is certainly something that I would completely avoid.

Rendering HTML inside textarea

An addendum to this. You can use character entities (such as changing <div> to &lt;div&gt;) and it will render in the textarea. But when it is saved, the value of the textarea is the text as rendered. So you don't need to de-encode. I just tested this across browsers (ie back to 11).

Consider defining a bean of type 'package' in your configuration [Spring-Boot]

You'll also get this error if you accidentally define the same bean in two different classes. That happened to me. The error message was misleading. When I removed the extra bean, the issue was resolved.

Select distinct values from a large DataTable column

This will retrun you distinct Ids

 var distinctIds = datatable.AsEnumerable()
                    .Select(s=> new {
                        id = s.Field<string>("id"),                           

How to suppress Pandas Future warning ?

Warnings are annoying. As mentioned in other answers, you can suppress them using:

import warnings
warnings.simplefilter(action='ignore', category=FutureWarning)

But if you want to handle them one by one and you are managing a bigger codebase, it will be difficult to find the line of code which is causing the warning. Since warnings unlike errors don't come with code traceback. In order to trace warnings like errors, you can write this at the top of the code:

import warnings

But if the codebase is bigger and it is importing bunch of other libraries/packages, then all sort of warnings will start to be raised as errors. In order to raise only certain type of warnings (in your case, its FutureWarning) as error, you can write:

import warnings
warnings.simplefilter(action='error', category=FutureWarning)

How to set back button text in Swift

I do not know where you have used your methods that you put on your question but I could get the desired result if I use, on my ViewController class (in which I want to change the back button), on viewDidLoad() function, the following line:

self.navigationController?.navigationBar.backItem?.title = "Anything Else"

The result will be:


enter image description here


enter image description here

CSS Background Image Not Displaying

if you are using vs code just try using background:url("img/bimg.jpg") instead of background:url('img/bimg.jpg') Mine worked at it Nothing much I replaced ' with "

SQL query: Delete all records from the table except latest N?

If your id is incremental then use something like

delete from table where id < (select max(id) from table)-N

How can we convert an integer to string in AngularJs

.toString() is available, or just add "" to the end of the int

var x = 3,
    toString = x.toString(),
    toConcat = x + "";

Angular is simply JavaScript at the core.

How to store a command in a variable in a shell script?

First of all there are functions for this. But if you prefer vars then your task can be done like this:

$ cmd=ls

$ $cmd # works
file  file2  test

$ cmd='ls | grep file'

$ $cmd # not works
ls: cannot access '|': No such file or directory
ls: cannot access 'grep': No such file or directory

$ bash -c $cmd # works
file  file2  test

$ bash -c "$cmd" # also works

$ bash <<< $cmd

$ bash <<< "$cmd"

Or via tmp file

$ tmp=$(mktemp)
$ echo "$cmd" > "$tmp"
$ chmod +x "$tmp"
$ "$tmp"

$ rm "$tmp"

proper hibernate annotation for byte[]

I got it work by overriding annotation with XML file for Postgres. Annotation is kept for Oracle. In my opinion, in this case it would be best we override the mapping of this trouble-some enity with xml mapping. We can override single / multiple entities with xml mapping. So we would use annotation for our mainly-supported database, and a xml file for each other database.

Note: we just need to override one single class , so it is not a big deal. Read more from my example Example to override annotation with XML

Difference between Constructor and ngOnInit

Constructor: The constructor method on an ES6 class (or TypeScript in this case) is a feature of a class itself, rather than an Angular feature. It’s out of Angular’s control when the constructor is invoked, which means that it’s not a suitable hook to let you know when Angular has finished initialising the component. JavaScript engine calls the constructor, not Angular directly. Which is why the ngOnInit (and $onInit in AngularJS) lifecycle hook was created. Bearing this in mind, there is a suitable scenario for using the constructor. This is when we want to utilise dependency injection - essentially for “wiring up” dependencies into the component.

As the constructor is initialised by the JavaScript engine, and TypeScript allows us to tell Angular what dependencies we require to be mapped against a specific property.

ngOnInit is purely there to give us a signal that Angular has finished initialising the component.

This phase includes the first pass at Change Detection against the properties that we may bind to the component itself - such as using an @Input() decorator.

Due to this, the @Input() properties are available inside ngOnInit, however are undefined inside the constructor, by design

How can I mock an ES6 module import using Jest?

The question is already answered, but you can resolve it like this:

File dependency.js

const doSomething = (x) => x
export default doSomething;

File myModule.js

import doSomething from "./dependency";

export default (x) => doSomething(x * 2);

File myModule.spec.js

import doSomething from "../dependency";
import myModule from "../myModule";

describe('myModule', () => {
  it('calls the dependency with double the input', () => {
    doSomething.mockImplementation((x) => x * 10)


    console.log(myModule(2)) // 40

How to redirect verbose garbage collection output to a file?

To add to the above answers, there's a good article: Useful JVM Flags – Part 8 (GC Logging) by Patrick Peschlow.

A brief excerpt:

The flag -XX:+PrintGC (or the alias -verbose:gc) activates the “simple” GC logging mode

By default the GC log is written to stdout. With -Xloggc:<file> we may instead specify an output file. Note that this flag implicitly sets -XX:+PrintGC and -XX:+PrintGCTimeStamps as well.

If we use -XX:+PrintGCDetails instead of -XX:+PrintGC, we activate the “detailed” GC logging mode which differs depending on the GC algorithm used.

With -XX:+PrintGCTimeStamps a timestamp reflecting the real time passed in seconds since JVM start is added to every line.

If we specify -XX:+PrintGCDateStamps each line starts with the absolute date and time.

Git ignore file for Xcode projects

Best of all,

Go and choose your language, and then it'll give you the file.

Creating/writing into a new file in Qt

QFile file("test.txt");
 *If file does not exist, it will be created
if (! | QIODevice::Text | QIODevice::ReadWrite))

/*for Reading line by line from text file*/
while (!file.atEnd()) {
    QByteArray line = file.readLine();
    qDebug() << "read output - " << line;

/*for writing line by line to text file */
if (
    QTextStream stream(&file);
    stream << "1_XYZ"<<endl;
    stream << "2_XYZ"<<endl;

Javascript Date - set just the date, ignoring time?

How about .toDateString()?

Alternatively, use .getDate(), .getMonth(), and .getYear()?

In my mind, if you want to group things by date, you simply want to access the date, not set it. Through having some set way of accessing the date field, you can compare them and group them together, no?

Check out all the fun Date methods here: MDN Docs

Edit: If you want to keep it as a date object, just do this:

var newDate = new Date(oldDate.toDateString());

Date's constructor is pretty smart about parsing Strings (though not without a ton of caveats, but this should work pretty consistently), so taking the old Date and printing it to just the date without any time will result in the same effect you had in the original post.

XPath query to get nth instance of an element

This is a FAQ:


means "Find every node selected by //somexpression that is the $Nth child of its parent".

What you want is:


Remember: The [] operator has higher precedence (priority) than the // abbreviation.

"Are you missing an assembly reference?" compile error - Visual Studio

Right-click the assembly reference in the solution explorer, properties, disable the "Specific Version" option.

Android: Create spinner programmatically from array

This worked for me with a string-array named shoes loaded from the projects resources:

Spinner              spinnerCountShoes = (Spinner)findViewById(;
ArrayAdapter<String> spinnerCountShoesArrayAdapter = new ArrayAdapter<String>(

This is my resource file (res/values/arrays.xml) with the string-array named shoes:

<?xml version="1.0" encoding="utf-8"?>
    <string-array name="shoes">

With this method it's easier to make it multilingual (if necessary).

Using if elif fi in shell scripts

Use double brackets...

if [[ expression ]]

How to detect if CMD is running as Administrator/has elevated privileges?

Here's a simple method I've used on Windows 7 through Windows 10. Basically, I simply use the "IF EXIST" command to check for the Windows\System32\WDI\LogFiles folder. The WDI folder exists on every install of Windows from at least 7 onward, and it requires admin privileges to access. The WDI folder always has a LogFiles folder inside it. So, running "IF EXIST" on the WDI\LogFiles folder will return true if run as admin, and false if not run as admin. This can be used in a batch file to check privilege level, and branch to whichever commands you desire based on that result.

Here's a brief snippet of example code:

(Commands for running with normal privileges)

(Commands for running with admin privileges)

Keep in mind that this method assumes the default security permissions have not been modified on the WDI folder (which is unlikely to happen in most situations, but please see caveat #2 below). Even in that case, it's simply a matter of modifying the code to check for a different common file/folder that requires admin access (System32\config\SAM may be a good alternate candidate), or you could even create your own specifically for that purpose.

There are two caveats about this method though:

  1. Disabling UAC will likely break it through the simple fact that everything would be run as admin anyway.

  2. Attempting to open the WDI folder in Windows Explorer and then clicking "Continue" when prompted will add permanent access rights for that user account, thus breaking my method. If this happens, it can be fixed by removing the user account from the WDI folder security permissions. If for any reason the user MUST be able to access the WDI folder with Windows Explorer, then you'd have to modify the code to check a different folder (as mentioned above, creating your own specifically for this purpose may be a good choice).

So, admittedly my method isn't perfect since it can be broken, but it's a relatively quick method that's easy to implement, is equally compatible with all versions of Windows 7, 8 and 10, and provided I stay mindful of the mentioned caveats has been 100% effective for me.

Automatically start forever (node) on system restart

The problem with rc.local is that the commands are accessed as root which is different than logging to as a user and using sudo.

I solved this problem by adding a .sh script with the startup commands i want to etc/profile.d. Any .sh file in profile.d will load automatically and any command will be treated as if you used the regular sudo.

The only downside to this is the specified user needs to loggin for things to start which in my situation was always the case.

How to submit form on change of dropdown list?

Simple JavaScript will do -

<form action="" method="POST">
    <select name="myselect" id="myselect" onchange="this.form.submit()">
        <option value="1">One</option>
        <option value="2">Two</option>
        <option value="3">Three</option>
        <option value="4">Four</option>

Here is a link for a good javascript tutorial.

How to create a hidden <img> in JavaScript?

This question is vague, but if you want to make the image with Javascript. It is simple.

function loadImages(src) {
  if (document.images) {
    img1 = new Image();
    img1.src = src;

The image will be requested but until you show it it will never be displayed. great for pre loading images you expect to be requests but delaying it until the document is loaded.


Using Mockito with multiple calls to the same method with the same arguments

How about

when( method-call ).thenReturn( value1, value2, value3 );

You can put as many arguments as you like in the brackets of thenReturn, provided they're all the correct type. The first value will be returned the first time the method is called, then the second answer, and so on. The last value will be returned repeatedly once all the other values are used up.

Exists Angularjs code/naming conventions?

Check out this GitHub repository that describes best practices for AngularJS apps. It has naming conventions for different components. It is not complete, but it is community-driven so everyone can contribute.

C# Macro definitions in Preprocessor

I would suggest you to write extension, something like below.

public static class WriteToConsoleExtension
   // Extension to all types
   public static void WriteToConsole(this object instance, 
                                     string format, 
                                     params object[] data)
       Console.WriteLine(format, data);

class Program
    static void Main(string[] args)
        Program p = new Program();
        // Usage of extension
        p.WriteToConsole("Test {0}, {1}", DateTime.Now, 1);

Hope this helps (and not too late :) )

USB Debugging option greyed out

Unplug your phone from the your computer, then choose PC Software as PC Connection Type. Then go into Developer Options and select USB Debugging

Convert an ISO date to the date format yyyy-mm-dd in JavaScript

let dt = new Date('2013-03-10T02:00:00Z');
let dd = dt.getDate();
let mm = dt.getMonth() + 1;
let yyyy = dt.getFullYear();

if (dd<10) {
    dd = '0' + dd;
if (mm<10) {
    mm = '0' + mm;
return yyyy + '-' + mm + '-' + dd;

Add MIME mapping in web.config for IIS Express

I'm not using IIS Express but developing against my Local Full IIS 7.

So if anyone else get's here trying to do that, I had to add the mime type for woff via IIS Manager

Mime Types >> Click Add link on right and then enter Extension: .woff MIME type: application/font-woff

How to solve : SQL Error: ORA-00604: error occurred at recursive SQL level 1

One possible explanation is a database trigger that fires for each DROP TABLE statement. To find the trigger, query the _TRIGGERS dictionary views:

select * from all_triggers
where trigger_type in ('AFTER EVENT', 'BEFORE EVENT')

disable any suspicious trigger with

   alter trigger <trigger_name> disable;

and try re-running your DROP TABLE statement

What is apache's maximum url length?

Allowed default size of URI is 8177 characters in GET request. Simple code in python for such testing.

#!/usr/bin/env python2

import sys
import socket

if __name__ == "__main__":
    string = sys.argv[1]
    buf_get = "x" * int(string)
    buf_size = 1024
    request = "HEAD %s HTTP/1.1\nHost:localhost\n\n" % buf_get
    print "===>", request

    sock_http = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock_http.connect(("localhost", 80))
    while True:
       print "==>", sock_http.recv(buf_size)
       if not sock_http.recv(buf_size):

On 8178 characters you will get such message: HTTP/1.1 414 Request-URI Too Large

PostgreSQL query to list all table names?

If you want list of database

SELECT datname FROM pg_database WHERE datistemplate = false;

If you want list of tables from current pg installation of all databases

SELECT table_schema,table_name FROM information_schema.tables
ORDER BY table_schema,table_name;

Playing m3u8 Files with HTML Video Tag

Use Flowplayer:

<link rel="stylesheet" href="//">

   <script src="//"></script>
  <script src="//"></script>
  <script src="//"></script> 
  flowplayer(function (api) {
    api.on("load", function (e, api, video) {
      $("#vinfo").text(api.engine.engineName + " engine playing " + video.type);
    }); });

<div class="flowplayer fixed-controls no-toggle no-time play-button obj"
      style="    width: 85.5%;
    height: 80%;
    margin-left: 7.2%;
    margin-top: 6%;
    z-index: 1000;" data-key="$812975748999788" data-live="true" data-share="false" data-ratio="0.5625"  data-logo="">
      <video autoplay="true" stretch="true">

         <source type="application/x-mpegurl" src="">

Different methods are available in website.

Typescript interface default values

You could use two separate configs. One as the input with optional properties (that will have default values), and another with only the required properties. This can be made convenient with & and Required:

interface DefaultedFuncConfig {
  b?: boolean;

interface MandatoryFuncConfig {
  a: boolean;

export type FuncConfig = MandatoryFuncConfig & DefaultedFuncConfig;
export const func = (config: FuncConfig): Required<FuncConfig> => ({
  b: true,

// will compile
func({ a: true });
func({ a: true, b: true });

// will error
func({ b: true });

How to use multiple conditions (With AND) in IIF expressions in ssrs

You don't need an IIF() at all here. The comparisons return true or false anyway.

Also, since this row visibility is on a group row, make sure you use the same aggregate function on the fields as you use in the fields in the row. So if your group row shows sums, then you'd put this in the Hidden property.

=Sum(Fields!OpeningStock.Value) = 0 And
Sum(Fields!GrossDispatched.Value) = 0 And 
Sum(Fields!TransferOutToMW.Value) = 0 And
Sum(Fields!TransferOutToDW.Value) = 0 And
Sum(Fields!TransferOutToOW.Value) = 0 And
Sum(Fields!NetDispatched.Value) = 0 And
Sum(Fields!QtySold.Value) = 0 And
Sum(Fields!StockAdjustment.Value) = 0 And
Sum(Fields!ClosingStock.Value) = 0

But with the above version, if one record has value 1 and one has value -1 and all others are zero then sum is also zero and the row could be hidden. If that's not what you want you could write a more complex expression:

        Fields!OpeningStock.Value=0 AND
        Fields!GrossDispatched.Value=0 AND
        Fields!TransferOutToMW.Value=0 AND
        Fields!TransferOutToDW.Value=0 AND 
        Fields!TransferOutToOW.Value=0 AND
        Fields!NetDispatched.Value=0 AND
        Fields!QtySold.Value=0 AND
        Fields!StockAdjustment.Value=0 AND
) = 0

This is essentially a fancy way of counting the number of rows in which any field is not zero. If every field is zero for every row in the group then the expression returns true and the row is hidden.

Find character position and update file name

If you split the filename on underscore and dot, you get an array of 3 strings. Join the first and third string, i.e. with index 0 and 2

$x = '237801_201011221155.xml' 
( $x.split('_.')[0] , $x.split('_.')[2] ) -join '.' 

Another way to do the same thing:

'237801_201011221155.xml'.split('_.')[0,2] -join '.'

Where Is Machine.Config?

  1. Open Windows Run command. Shortcut=> windows key + r
  2. Type "" - MS .Net folder opens up
  3. Open "Framework"/"Framework64" folder(based on your processor).
  4. Select specific FW version folder e.g. "v4.0.30319"
  5. Open config folder
  6. Machine.config will be available there. Cheers.

Using If/Else on a data frame

Use ifelse:

frame$twohouses <- ifelse(frame$data>=2, 2, 1)
   data twohouses
1     0         1
2     1         1
3     2         2
4     3         2
5     4         2
16    0         1
17    2         2
18    1         1
19    2         2
20    0         1
21    4         2

The difference between if and ifelse:

  • if is a control flow statement, taking a single logical value as an argument
  • ifelse is a vectorised function, taking vectors as all its arguments.

The help page for if, accessible via ?"if" will also point you to ?ifelse

Trying to get Laravel 5 email to work

In my case: Restart the server and run php artisan config:clear command.

HTML5 placeholder css padding

I got the same issue.

I fixed it by removing line-height from my input. Check if there is some lineheight which is causing the problem

Git commit with no commit message

You don't need git to accomplish this. Creative use of a bash function will do the trick just fine. If you don't care about messages, just set a default one and forget it.

function gitcom() {
  git commit -m "my default commit message"

If you were feeling really adventurous you could add, commit and push with one command

function gitzap() {
  git add . && git commit -m "whatevs" && git push $1 $2

Which you would then run as

gitzap origin master

You could even get deeper and use parse_git_branch to save yourself some keystrokes there, or set a common default of "origin" and "master".

How do I show running processes in Oracle DB?

I suspect you would just want to grab a few columns from V$SESSION and the SQL statement from V$SQL. Assuming you want to exclude the background processes that Oracle itself is running

SELECT sess.process, sess.status, sess.username, sess.schemaname, sql.sql_text
  FROM v$session sess,
       v$sql     sql
 WHERE sql.sql_id(+) = sess.sql_id
   AND sess.type     = 'USER'

The outer join is to handle those sessions that aren't currently active, assuming you want those. You could also get the sql_fulltext column from V$SQL which will have the full SQL statement rather than the first 1000 characters, but that is a CLOB and so likely a bit more complicated to deal with.

Realistically, you probably want to look at everything that is available in V$SESSION because it's likely that you can get a lot more information than SP_WHO provides.

Substitute multiple whitespace with single whitespace in Python

A simple possibility (if you'd rather avoid REs) is

' '.join(mystring.split())

The split and join perform the task you're explicitly asking about -- plus, they also do the extra one that you don't talk about but is seen in your example, removing trailing spaces;-).

Find element's index in pandas Series

you can use Series.idxmax()

>>> import pandas as pd
>>> myseries = pd.Series([1,4,0,7,5], index=[0,1,2,3,4])
>>> myseries.idxmax()

How to reposition Chrome Developer Tools

After I have placed my dock to the right (see older answers), I still found the panels split vertically.

To split the panels horizontally - and even got more from your screen width - go to Settings (bottom right corner), and remove the check on 'Split panels vertically when docked to right'.

Now, you have all panels from left to right :p

How to find out what the date was 5 days ago?

Try this

$date = date("Y-m-d", strtotime("-5 day"));

Android Studio : How to uninstall APK (or execute adb command) automatically before Run or Debug?

adb uninstall <package_name>

can be used to uninstall an app via your PC. If you want this to happen automatically every time you launch your app via Android Studio, you can do this:

  1. In Android Studio, click the drop down list to the left of Run button, and select Edit configurations...
  2. Click on app under Android Application, and in General Tab, find the heading 'Before Launch'
  3. Click the + button, select Run external tool, click the + button in the popup window.
  4. Give some name (Eg adb uninstall) and description, and type adb in Program: and uninstall <your-package-name> in Parameters:. Make sure that the new item is selected when you click Ok in the popup window.

Note: If you do not have adb in your PATH environment variable, give the full path to adb in Program: field (eg /home/user/android/sdk/platform-tools/adb).

Moment.js - How to convert date string into date?

if you have a string of date, then you should try this.

const FORMAT = "YYYY ddd MMM DD HH:mm";

const theDate = moment("2019 Tue Apr 09 13:30", FORMAT);
// Tue Apr 09 2019 13:30:00 GMT+0300

const theDate1 = moment("2019 Tue Apr 09 13:30", FORMAT).format('LL')
// April 9, 2019

or try this :

const theDate1 = moment("2019 Tue Apr 09 13:30").format(FORMAT);

Selecting data frame rows based on partial string match in a column

I notice that you mention a function %like% in your current approach. I don't know if that's a reference to the %like% from "data.table", but if it is, you can definitely use it as follows.

Note that the object does not have to be a data.table (but also remember that subsetting approaches for data.frames and data.tables are not identical):

mtcars[rownames(mtcars) %like% "Merc", ]
iris[iris$Species %like% "osa", ]

If that is what you had, then perhaps you had just mixed up row and column positions for subsetting data.

If you don't want to load a package, you can try using grep() to search for the string you're matching. Here's an example with the mtcars dataset, where we are matching all rows where the row names includes "Merc":

mtcars[grep("Merc", rownames(mtcars)), ]
             mpg cyl  disp  hp drat   wt qsec vs am gear carb
# Merc 240D   24.4   4 146.7  62 3.69 3.19 20.0  1  0    4    2
# Merc 230    22.8   4 140.8  95 3.92 3.15 22.9  1  0    4    2
# Merc 280    19.2   6 167.6 123 3.92 3.44 18.3  1  0    4    4
# Merc 280C   17.8   6 167.6 123 3.92 3.44 18.9  1  0    4    4
# Merc 450SE  16.4   8 275.8 180 3.07 4.07 17.4  0  0    3    3
# Merc 450SL  17.3   8 275.8 180 3.07 3.73 17.6  0  0    3    3
# Merc 450SLC 15.2   8 275.8 180 3.07 3.78 18.0  0  0    3    3

And, another example, using the iris dataset searching for the string osa:

irisSubset <- iris[grep("osa", iris$Species), ]
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

For your problem try:

selectedRows <- conservedData[grep("hsa-", conservedData$miRNA), ]

forcing web-site to show in landscape mode only

While I myself would be waiting here for an answer, I wonder if it can be done via CSS:

@media only screen and (orientation:portrait){
#wrapper {width:1024px}

@media only screen and (orientation:landscape){
#wrapper {width:1024px}

Find most frequent value in SQL column

SELECT       `column`,
             COUNT(`column`) AS `value_occurrence` 
    FROM     `my_table`
    GROUP BY `column`
    ORDER BY `value_occurrence` DESC
    LIMIT    1;

Replace column and my_table. Increase 1 if you want to see the N most common values of the column.

How to get main window handle from process id?

I checked how .NET determines the main window.

My finding showed that it also uses EnumWindows().

This code should do it similarly to the .NET way:

struct handle_data {
    unsigned long process_id;
    HWND window_handle;

HWND find_main_window(unsigned long process_id)
    handle_data data;
    data.process_id = process_id;
    data.window_handle = 0;
    EnumWindows(enum_windows_callback, (LPARAM)&data);
    return data.window_handle;

BOOL CALLBACK enum_windows_callback(HWND handle, LPARAM lParam)
    handle_data& data = *(handle_data*)lParam;
    unsigned long process_id = 0;
    GetWindowThreadProcessId(handle, &process_id);
    if (data.process_id != process_id || !is_main_window(handle))
        return TRUE;
    data.window_handle = handle;
    return FALSE;   

BOOL is_main_window(HWND handle)
    return GetWindow(handle, GW_OWNER) == (HWND)0 && IsWindowVisible(handle);

Description for event id from source cannot be found

I got this error after creating an event source under the Application Log from the command line using "EventCreate". This command creates a new key under: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Eventlog\Application

If you look at the Key that's been created (e.g. SourceTest) there will be a string value calledEventMessageFile, which for me was set to %SystemRoot%\System32\EventCreate.exe.

Change this to c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\EventLogMessages.dll

Delete theCustomSource and TypesSupported values.

This should stop the "The description for Event ID...." message.

Chrome javascript debugger breakpoints don't do anything?

I had an issue where Chrome's breakpoints weren't firing anything. When I tried to use 'debugger' in my code, I could only step through the code in the VM version of my code. My issue was that I was mapping the resources incorrectly. Re-mapping fixed my problem.

Can I set the cookies to be used by a WKWebView?

The cookies must be set on the configuration before the WKWebView is created. Otherwise, even with WKHTTPCookieStore's setCookie completion handler, the cookies won't reliably be synced to the web view. This goes back to this line from the docs on WKWebViewConfiguration

@NSCopying var configuration: WKWebViewConfiguration { get }

That @NSCopying is somewhat of a deep copy. The implementation is beyond me, but the end result is that unless you set cookies before initializing the webview, you can't count on the cookies being there. This can complicate app architecture because initializing a view becomes an asynchronous process. You'll end up with something like this

extension WKWebViewConfiguration {
    /// Async Factory method to acquire WKWebViewConfigurations packaged with system cookies
    static func cookiesIncluded(completion: @escaping (WKWebViewConfiguration?) -> Void) {
        let config = WKWebViewConfiguration()
        guard let cookies = HTTPCookieStorage.shared.cookies else {
        // Use nonPersistent() or default() depending on if you want cookies persisted to disk
        // and shared between WKWebViews of the same app (default), or not persisted and not shared
        // across WKWebViews in the same app.
        let dataStore = WKWebsiteDataStore.nonPersistent()
        let waitGroup = DispatchGroup()
        for cookie in cookies {
            dataStore.httpCookieStore.setCookie(cookie) { waitGroup.leave() }
        waitGroup.notify(queue: DispatchQueue.main) {
            config.websiteDataStore = dataStore

and then to use it something like

override func loadView() {
    view = UIView()
    WKWebViewConfiguration.cookiesIncluded { [weak self] config in
        let webView = WKWebView(frame: .zero, configuration: webConfiguration)
        self.view = webView

The above example defers view creation until the last possible moment, another solution would be to create the config or webview well in advance and handle the asynchronous nature before creation of a view controller.

A final note: once you create this webview, you have set it loose into the wild, you can't add more cookies without using methods described in this answer. You can however use the WKHTTPCookieStoreObserver api to at least observe changes happening to cookies. So if a session cookie gets updated in the webview, you can manually update the system's HTTPCookieStorage with this new cookie if desired.

For more on this, skip to 18:00 at this 2017 WWDC Session Custom Web Content Loading. At the beginning of this session, there is a deceptive code sample which omits the fact that the webview should be created in the completion handler.

cookieStore.setCookie(cookie!) {

The live demo at 18:00 clarifies this.

Edit As of Mojave Beta 7 and iOS 12 Beta 7 at least, I'm seeing much more consistent behavior with cookies. The setCookie(_:) method even appears to allow setting cookies after the WKWebView has been created. I did find it important though, to not touch the processPool variable at all. The cookie setting functionality works best when no additional pools are created and when that property is left well alone. I think it's safe to say we were having issues due to some bugs in WebKit.

Change primary key column in SQL Server

Assuming that your current primary key constraint is called pk_history, you can replace the following lines:



with these:



If you don't know what the name of the PK is, you can find it with the following query:

 WHERE TABLE_NAME = 'history'

How do I resolve ClassNotFoundException?

sorry i am late to the question, but i will explain it to you in the simplest layman language. When you type 'javac <> The compiler checks the program and finds errors, first of all make sure your program is in the same directory as you have executed in the command prompt. Then it creates a. Class file of your program. For ex. If the name of my program was then the class file created should be Test.class which will be executed in the next line. Sometimes java takes some other name for your .class, use that name and voila you'll get the output.

Convert list of ints to one number?

def magic(numbers):
    return int(''.join([ "%d"%x for x in numbers]))

Android emulator doesn't take keyboard input - SDK tools rev 20

Look for the hidden .android folder in your user home folder. You might rename or delete this folder, recreate your AVD, and restart the emulator. It could be there is a .ini file in that folder that has that setting munged.

What is the difference between SQL, PL-SQL and T-SQL?

SQL is a standard and there are many database vendors like Microsoft,Oracle who implements this standard using their own proprietary language.

Microsoft uses T-SQL to implement SQL standard to interact with data whereas oracle uses PL/SQL.

How to add /usr/local/bin in $PATH on Mac

Try placing $PATH at the end.

export PATH=/usr/local/git/bin:/usr/local/bin:$PATH

json_encode(): Invalid UTF-8 sequence in argument

Seems like the symbol was Å, but since data consists of surnames that shouldn't be public, only first letter was shown and it was done by just $lastname[0], which is wrong for multibyte strings and caused the whole hassle. Changed it to mb_substr($lastname, 0, 1) - works like a charm.

Subtracting two lists in Python

You can try something like this:

class mylist(list):

    def __sub__(self, b):
        result = self[:]
        b = b[:]
        while b:
            except ValueError:
                raise Exception("Not all elements found during subtraction")
        return result

a = mylist([0, 1, 2, 1, 0] )
b = mylist([0, 1, 1])

>>> a - b
[2, 0]

You have to define what [1, 2, 3] - [5, 6] should output though, I guess you want [1, 2, 3] thats why I ignore the ValueError.

Edit: Now I see you wanted an exception if a does not contain all elements, added it instead of passing the ValueError.

Pandas - Compute z-score for all columns

The almost one-liner solution:

df2 = (df.ix[:,1:] - df.ix[:,1:].mean()) / df.ix[:,1:].std()
df2['ID'] = df['ID']

How do I find out what keystore my JVM is using?

As DimtryB mentioned, by default the keystore is under the user directory. But if you are trying to update the cacerts file, so that the JVM can pick the keys, then you will have to update the cacerts file under jre/lib/security. You can also view the keys by executing the command keytool -list -keystore cacerts to see if your certificate is added.

How to delete a cookie using jQuery?

it is the problem of misunderstand of cookie. Browsers recognize cookie values for not just keys also compare the options path & domain. So Browsers recognize different value which cookie values that key is 'name' with server setting option(path='/'; domain='') and key is 'name' with no option.

Listing all permutations of a string/integer

Here is an easy to understand permutaion function for both string and integer as input. With this you can even set your output length(which in normal case it is equal to input length)


    static ICollection<string> result;

    public static ICollection<string> GetAllPermutations(string str, int outputLength)
        result = new List<string>();
        MakePermutations(str.ToCharArray(), string.Empty, outputLength);
        return result;

    private static void MakePermutations(
       char[] possibleArray,//all chars extracted from input
       string permutation,
       int outputLength//the length of output)
         if (permutation.Length < outputLength)
             for (int i = 0; i < possibleArray.Length; i++)
                 var tempList = possibleArray.ToList<char>();
                      string.Concat(permutation, possibleArray[i]), outputLength);
         else if (!result.Contains(permutation))

and for Integer just change the caller method and MakePermutations() remains untouched:

    public static ICollection<int> GetAllPermutations(int input, int outputLength)
        result = new List<string>();
        MakePermutations(input.ToString().ToCharArray(), string.Empty, outputLength);
        return result.Select(m => int.Parse(m)).ToList<int>();

example 1: GetAllPermutations("abc",3); "abc" "acb" "bac" "bca" "cab" "cba"

example 2: GetAllPermutations("abcd",2); "ab" "ac" "ad" "ba" "bc" "bd" "ca" "cb" "cd" "da" "db" "dc"

example 3: GetAllPermutations(486,2); 48 46 84 86 64 68

How to add bootstrap in angular 6 project?

npm install bootstrap --save

and add relevent files into angular.json file under the style property for css files and under scripts for JS files.

 "styles": [

SQL alias for SELECT statement

You can do this using the WITH clause of the SELECT statement:

WITH my_select As (SELECT ... FROM ...) 
WHERE id IN (SELECT MAX(id) FROM my_select GROUP BY name)

That's the ANSI/ISO SQL Syntax. I know that SQL Server, Oracle and DB2 support it. Not sure about the others...

How can I get a side-by-side diff when I do "git diff"?

Although Git has an internal implementation of diff, you can set up an external tool instead.

There are two different ways to specify an external diff tool:

  1. setting the GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables.
  2. configuring the external diff tool via git config

See also:

When doing a git diff, Git checks both the settings of above environment variables and its .gitconfig file.

By default, Git passes the following seven arguments to the diff program:

path  old-file  old-hex old-mode  new-file  new-hex new-mode

You typically only need the old-file and new-file parameters. Of course most diff tools only take two file names as an argument. This means that you need to write a small wrapper-script, which takes the arguments which Git provides to the script, and hands them on to the external git program of your choice.

Let's say you put your wrapper-script under ~/scripts/

# un-comment one diff tool you'd like to use

# side-by-side diff with custom options:
# /usr/bin/sdiff -w200 -l "$2" "$5" 

# using kdiff3 as the side-by-side diff:
# /usr/bin/kdiff3 "$2" "$5"

# using Meld 
/usr/bin/meld "$2" "$5"

# using VIM
# /usr/bin/vim -d "$2" "$5"

you then need to make that script executable:

chmod a+x ~/scripts/

you then need to tell Git how and where to find your custom diff wrapper script. You have three choices how to do that: (I prefer editing the .gitconfig file)


    e.g. in your .bashrc or .bash_profile file you can set:

  2. Using git config

    use "git config" to define where your wrapper script can be found:

    git config --global diff.external ~/scripts/
  3. Editing your ~/.gitconfig file

    you can edit your ~/.gitconfig file to add these lines:

      external = ~/scripts/


Similarly to installing your custom diff tool, you can also install a custom merge-tool, which could be a visual merging tool to better help visualizing the merge. (see the page)

See: and

MVC : The parameters dictionary contains a null entry for parameter 'k' of non-nullable type 'System.Int32'

I faced this error becouse I sent the Query string with wrong format

--------------------------------------------must be &

so make sure your Query String or passed parameter in the right format

Compiler error: memset was not declared in this scope

Whevever you get a problem like this just go to the man page for the function in question and it will tell you what header you are missing, e.g.

$ man memset

MEMSET(3)                BSD Library Functions Manual                MEMSET(3)

     memset -- fill a byte string with a byte value

     Standard C Library (libc, -lc)

     #include <string.h>

     void *
     memset(void *b, int c, size_t len);

Note that for C++ it's generally preferable to use the proper equivalent C++ headers, <cstring>/<cstdio>/<cstdlib>/etc, rather than C's <string.h>/<stdio.h>/<stdlib.h>/etc.

Hibernate: Automatically creating/updating the db tables based on entity classes

I don't know if leaving hibernate off the front makes a difference.

The reference suggests it should be

A value of create will create your tables at sessionFactory creation, and leave them intact.

A value of create-drop will create your tables, and then drop them when you close the sessionFactory.

Perhaps you should set the javax.persistence.Table annotation explicitly?

Hope this helps.

need to add a class to an element

Try using setAttribute on the result:


What are sessions? How do they work?

Think of HTTP as a person(A) who has SHORT TERM MEMORY LOSS and forgets every person as soon as that person goes out of sight.

Now, to remember different persons, A takes a photo of that person and keeps it. Each Person's pic has an ID number. When that person comes again in sight, that person tells it's ID number to A and A finds their picture by ID number. And voila !!, A knows who is that person.

Same is with HTTP. It is suffering from SHORT TERM MEMORY LOSS. It uses Sessions to record everything you did while using a website, and then, when you come again, it identifies you with the help of Cookies(Cookie is like a token). Picture is the Session here, and ID is the Cookie here.

How to add jQuery code into HTML Page

Make sure that you embedd the jQuery library into your page by adding the below shown line into your <head> block:

<script src=""></script>

SOAP or REST for Web Services?

It's a good question... I don't want to lead you astray, so I'm open to other people's answers as much as you are. For me, it really comes down to cost of overhead and what the use of the API is. I prefer consuming web services when creating client software, however I don't like the weight of SOAP. REST, I believe, is lighter weight but I don't enjoy working with it from a client perspective nearly as much.

I'm curious as to what others think.

Checking Value of Radio Button Group via JavaScript?

function myFunction() {_x000D_
 document.getElementById("myCheck_2").checked = false;_x000D_
  var checkBox = document.getElementById("myCheck");_x000D_
  var text = document.getElementById("text");_x000D_
  if (checkBox.checked == true){_x000D_ = "block";_x000D_
  } else {_x000D_ = "none";_x000D_
function myFunction_2() {_x000D_
 document.getElementById("myCheck").checked = false;_x000D_
  var checkBox = document.getElementById("myCheck_2");_x000D_
  var text = document.getElementById("text");_x000D_
  if (checkBox.checked == true){_x000D_ = "block";_x000D_
  } else {_x000D_ = "none";_x000D_
Male: <input type="checkbox" id="myCheck"  onclick="myFunction()">_x000D_
Female: <input type="checkbox" id="myCheck_2"  onclick="myFunction_2()">_x000D_
<input type="text" id="text" placeholder="Name">

What are advantages of Artificial Neural Networks over Support Vector Machines?

We should also consider that the SVM system can be applied directly to non-metric spaces, such as the set of labeled graphs or strings. In fact, the internal kernel function can be generalized properly to virtually any kind of input, provided that the positive definiteness requirement of the kernel is satisfied. On the other hand, to be able to use an ANN on a set of labeled graphs, explicit embedding procedures must be considered.

How to paste into a terminal?

On windows 7:

Ctrl + Shift + Ins

works for me!