Programs & Examples On #Invocation api

Get index of a key/value pair in a C# dictionary based on the value

Let's say you have a Dictionary called fooDictionary


Values.ToList() converts your dictionary values into a List of someValue objects.

IndexOf(someValue) searches your new List looking for the someValue object in question and returns the Index which would match the index of the Key/Value pair in the dictionary.

This method does not care about the dictionary keys, it simply returns the index of the value that you are looking for.

This does not however account for the issue that there may be several matching "someValue" objects.

Showing percentages above bars on Excel column graph

You can do this with a pivot table and add a line with the pourcentage for each category like brettdj showed in his answer. But if you want to keep your data as it is, there is a solution by using some javascript.

Javascript is a powerful language offering a lot of useful data visualization libraries like plotly.js.

Here is a working code I have written for you:

In this example, I use a Json file to get the data from the embedded spreadsheet, so I can use it in my javascript code and create a bar chart.

I calculate the percentage by adding the values of all the category present in the table and using this formula (you can see it in the script.js file): Percentage (%) = 100 x partial value / total value

It automatically calculates the total and pourcentage even if you add more categories.

I used plotly.js to create my chart, it has a good documentation and lots of examples for beginners, this code gets all the option you want to use:

var trace1 = {
    x: xValue, 
    y: data,
    type: 'bar',
    text: yValue,
    textposition: 'auto',
    hoverinfo: 'none',
    marker: {
    color: 'yellow',
    opacity: 0.6,
    line: {
      color: 'yellow',
      width: 1.5

It is rather self explanatory, the text is where you put the percentage.

Once you've made your chart you can load it in excel by passing the URL in the Funfun add-in. Here is how it looks like with my example:


I know it is an old post but I hope it helps people with the same problem !

Disclosure : I’m a developer of funfun

Creating and Update Laravel Eloquent

$shopOwner = ShopMeta::firstOrNew(array('shopId' => $theID,'metadataKey' => 2001));

Then make your changes and save. Note the firstOrNew doesn't do the insert if its not found, if you do need that then its firstOrCreate.

How to convert webpage into PDF by using Python

here is the one working fine:

import sys 
from PyQt4.QtCore import *
from PyQt4.QtGui import * 
from PyQt4.QtWebKit import * 

app = QApplication(sys.argv)
web = QWebView()
printer = QPrinter()

def convertIt():
    print("Pdf generated")

QObject.connect(web, SIGNAL("loadFinished(bool)"), convertIt)

How to lock orientation of one view controller to portrait mode only in Swift

Things can get quite messy when you have a complicated view hierarchy, like having multiple navigation controllers and/or tab view controllers.

This implementation puts it on the individual view controllers to set when they would like to lock orientations, instead of relying on the App Delegate to find them by iterating through subviews.

Swift 3, 4, 5

In AppDelegate:

/// set orientations you want to be allowed in this property by default
var orientationLock = UIInterfaceOrientationMask.all

func application(_ application: UIApplication, supportedInterfaceOrientationsFor window: UIWindow?) -> UIInterfaceOrientationMask {
        return self.orientationLock

In some other global struct or helper class, here I created AppUtility:

struct AppUtility {

    static func lockOrientation(_ orientation: UIInterfaceOrientationMask) {
        if let delegate = UIApplication.shared.delegate as? AppDelegate {
            delegate.orientationLock = orientation

    /// OPTIONAL Added method to adjust lock and rotate to the desired orientation
    static func lockOrientation(_ orientation: UIInterfaceOrientationMask, andRotateTo rotateOrientation:UIInterfaceOrientation) {
        UIDevice.current.setValue(rotateOrientation.rawValue, forKey: "orientation")


Then in the desired ViewController you want to lock orientations:

 override func viewWillAppear(_ animated: Bool) {
    // Or to rotate and lock
    // AppUtility.lockOrientation(.portrait, andRotateTo: .portrait)

override func viewWillDisappear(_ animated: Bool) {
    // Don't forget to reset when view is being removed

If iPad or Universal App

Make sure that "Requires full screen" is checked in Target Settings -> General -> Deployment Info. supportedInterfaceOrientationsFor delegate will not get called if that is not checked. enter image description here

Maintain image aspect ratio when changing height

Actually I found out that the container of the image tag need to have a height in order to keep the ratio of the image. for example>

.container{display:flex; height:100%;} img{width:100%;height:auto;}

then in your html your container will wrap the tag image

<div class="container"><img src="image.jpg" alt="image" /></div>

this work for IE and other browsers

Matplotlib subplots_adjust hspace so titles and xlabels don't overlap?

You can use plt.subplots_adjust to change the spacing between the subplots Link

subplots_adjust(left=None, bottom=None, right=None, top=None, wspace=None, hspace=None)

left  = 0.125  # the left side of the subplots of the figure
right = 0.9    # the right side of the subplots of the figure
bottom = 0.1   # the bottom of the subplots of the figure
top = 0.9      # the top of the subplots of the figure
wspace = 0.2   # the amount of width reserved for blank space between subplots
hspace = 0.2   # the amount of height reserved for white space between subplots

How to cast from List<Double> to double[] in Java?

As per your question,

List<Double> frameList =  new ArrayList<Double>();
  1. First you have to convert List<Double> to Double[] by using

    Double[] array = frameList.toArray(new Double[frameList.size()]);
  2. Next you can convert Double[] to double[] using

    double[] doubleArray = ArrayUtils.toPrimitive(array);

You can directly use it in one line:

double[] array = ArrayUtils.toPrimitive(frameList.toArray(new Double[frameList.size()]));

ASP.NET Identity reset password

On your UserManager, first call GeneratePasswordResetTokenAsync. Once the user has verified his identity (for example by receiving the token in an email), pass the token to ResetPasswordAsync.

Running Selenium WebDriver python bindings in chrome

There are 2 ways to run Selenium python tests in Google Chrome. I'm considering Windows (Windows 10 in my case):

Prerequisite: Download the latest Chrome Driver from:

Way 1:

i) Extract the downloaded zip file in a directory/location of your choice
ii) Set the executable path in your code as below:

self.driver = webdriver.Chrome(executable_path='D:\Selenium_RiponAlWasim\Drivers\chromedriver_win32\chromedriver.exe')

Way 2:

i) Simply paste the chromedriver.exe under /Python/Scripts/ (In my case the folder was: C:\Python36\Scripts)
ii) Now write the simple code as below:

self.driver = webdriver.Chrome()

Deny all, allow only one IP through htaccess

Slightly modified version of the above, including a custom page to be displayed to those who get denied access:

ErrorDocument 403 /specific_page.html
order deny,allow
deny from all
allow from 111.222.333.444

...and that way those requests not coming from 111.222.333.444 will see specific_page.html

(posting this as comment looked terrible because new lines get lost)

How do I make a new line in swift

"\n" is not working everywhere!

For example in email, it adds the exact "\n" into the text instead of a new line if you use it in the custom keyboard like: textDocumentProxy.insertText("\n")

There are another newLine characters available but I can't just simply paste them here (Because they make a new lines).

using this extension:

extension CharacterSet {
    var allCharacters: [Character] {
        var result: [Character] = []
        for plane: UInt8 in 0...16 where self.hasMember(inPlane: plane) {
            for unicode in UInt32(plane) << 16 ..< UInt32(plane + 1) << 16 {
                if let uniChar = UnicodeScalar(unicode), self.contains(uniChar) {
        return result

you can access all characters in any CharacterSet. There is a character set called newlines. Use one of them to fulfill your requirements:

let newlines = CharacterSet.newlines.allCharacters
for newLine in newlines {
    print("Hello World \(newLine) This is a new line")

Then store the one you tested and worked everywhere and use it anywhere. Note that you can't relay on the index of the character set. It may change.

But most of the times "\n" just works as expected.

Allow multiple roles to access controller action

Another option is to use a single authorize filter as you posted but remove the inner quotations.


How to sort dates from Oldest to Newest in Excel?

Saw this ages after posting, but if anyone has the same problem I had, my dates were all the format DD.MM.YYYY (SPSS output) even formatting them to date in Excel still only let me sort from A-Z so basically the 1st-31st irrelevant of month.

Doing a find and replace of all "." to "/" fixed this so that they are now in the format of DD/MM/YYYY. Not sure why it didn't work in the other format when the cell type counted as date.

Loop through array of values with Arrow Function

In short:

someValues.forEach((element) => {

If you care about index, then second parameter can be passed to receive the index of current element:

someValues.forEach((element, index) => {
    console.log(`Current index: ${index}`);

Refer here to know more about Array of ES6:

How to Import .bson file format on mongodb

Run the following from command line and you should be in the Mongo bin directory.

mongorestore -d db_name -c collection_name path/file.bson

How to save an activity state using save instance state?

Meanwhile I do in general no more use

Bundle savedInstanceState & Co

The life cycle is for most activities too complicated and not necessary.

And Google states itself, it is NOT even reliable.

My way is to save any changes immediately in the preferences:

 SharedPreferences p;

In some way SharedPreferences work similar like Bundles. And naturally and at first such values have to be read from preferences.

In the case of complex data you may use SQLite instead of using preferences.

When applying this concept, the activity just continues to use the last saved state, regardless of whether it was an initial open with reboots in between or a reopen due to the back stack.

Call PowerShell script PS1 from another PS1 script inside Powershell ISE

This is just additional info to answers in order to pass argument into the another file

Where you expect argument


    [Parameter( Mandatory = $true)]
    $printName = "Joe"    

Write-Host $printName

How to call the file

    [Parameter( Mandatory = $false)]
    $name = "Joe"    

& ((Split-Path $MyInvocation.InvocationName) + "\PrintName.ps1") -printName $name

If you do not do not provide any input it will default to "Joe" and this will be passed as argument into printName argument in PrintName.ps1 file which will in turn print out the "Joe" string

How to remove all listeners in an element?

If you’re not opposed to jquery, this can be done in one line:

jQuery 1.7+


jQuery < 1.7


Here’s an example:

What is the javascript filename naming convention?

The question in the link you gave talks about naming of JavaScript variables, not about file naming, so forget about that for the context in which you ask your question.

As to file naming, it is purely a matter of preference and taste. I prefer naming files with hyphens because then I don't have to reach for the shift key, as I do when dealing with camelCase file names; and because I don't have to worry about differences between Windows and Linux file names (Windows file names are case-insensitive, at least through XP).

So the answer, like so many, is "it depends" or "it's up to you."

The one rule you should follow is to be consistent in the convention you choose.

How to remove the focus from a TextBox in WinForms?

The way I get around it is to place all my winform controls. I make all labels and non-selecting winform controls as tab order 0, then my first control as tab order 2 and then increment each selectable control's order by 1, so 3, 4, 5 etc...

This way, when my Winforms start up, the first TextBox doesn't have focus!

'cannot open git-upload-pack' error in Eclipse when cloning or pushing git repository

Finally I made it work thanks to the steps outlined in the Eclipse forum:

Set up the SSH key stuff

  1. Download and install mysys git according to the github instructions at
  2. In C:/Users/you/ssh hide any existing keys (id_rsa and in a subdirectory. If the ssh directory does not exist, create it. Of course, "you" is your username as the OS knows you.
  3. From the start menu, run Git-Bash command shell (a regular DOS command shell will not work).
  4. In the Git-Bash shell generate an rsa key based on your email (the one you registered at github): ssh-keygen -t rsa -C "[email protected]" and enter your pass phrase and confirm when asked.
  5. The previous step should have created C:/User/you/ssh/ which you can now open in a text editor and copy. At github, go to account settings, SSH Keys, add a key and paste this in the key box.
  6. In Git-Bash again (notice the back-ticks in the next line): eval `ssh-agent` ssh-add C:/User/you/ssh/id_rsa ssh [email protected]

Here is what you just did: You ran the ssh-agent which is needed by ssh-add. Then you used ssh-add to make note of the location of your key. Then you tried to ssh to GitHub. The response to this last command should be that you have successfully authenticated at GitHub but that you don't have shell access. This is just an authentication test. If the authentication was not successful, you'll have to sort that out. Try the verbose version:

ssh -v [email protected]

Assuming this worked....

In Eclipse, configure the remote push

  1. Window > Show View > Git > Git Repositories will add a repository explorer window.
  2. In the repository window, select the repository and expand and right-click Remotes and choose Create Remote.
  3. Copy the GitHub repository URI from the GitHub repository page and paste it in the URI box.
  4. Select ssh as the protocol but then go back to the URI box and add "git+" at the beginning so it looks like this:

    git+ssh://[email protected]/UserName/ProjectName.git

  5. In the Repository Path box, remove the leading slash

  6. Hit Next and cross your fingers. If your get "auth fail", restart Eclipse and try step 5 again.
  7. When you get past the authentication, in the next dialog select "master" for source ref, click "Add all branches spec" and "Finish".

Instead of using SSH [email protected] I did it with SSH [email protected].

Now I can push and import without any problem.

Add a month to a Date

It is ambiguous when you say "add a month to a date".

Do you mean

  1. add 30 days?
  2. increase the month part of the date by 1?

In both cases a whole package for a simple addition seems a bit exaggerated.

For the first point, of course, the simple + operator will do:

d + 30 
#[1] "2010-01-31"

As for the second I would just create a one line function as simple as that (and with a more general scope):

add.months= function(date,n) seq(date, by = paste (n, "months"), length = 2)[2]

You can use it with arbitrary months, including negative:

add.months(d, 3)
#[1] "2010-04-01"
add.months(d, -3)
#[1] "2009-10-01"

Of course, if you want to add only and often a single month:

add.month=function(date) add.months(date,1)
#[1] "2010-02-01"

If you add one month to 31 of January, since 31th February is meaningless, the best to get the job done is to add the missing 3 days to the following month, March. So correctly:

#[1] "2010-03-03"

In case, for some very special reason, you need to put a ceiling to the last available day of the month, it's a bit longer:

add.months.ceil=function (date, n){

  #no ceiling
  nC=add.months(date, n)

  C=add.months(date, n+1)-1

  #use ceiling in case of overlapping
  if(nC>C) return(C)

As usual you could add a single month version:

add.month.ceil=function(date) add.months.ceil(date,1)    


  #[1] "2010-02-28"
  #[1] "2010-02-21"

And with decrements:

  add.months.ceil(d, -1)
  #[1] "2010-02-28"
  add.months.ceil(d, -1)
  #[1] "2010-02-21"

Besides you didn't tell if you were interested to a scalar or vector solution. As for the latter:

add.months.v= function(date,n) as.Date(sapply(date, add.months, n), origin="1970-01-01")

Note: *apply family destroys the class data, that's why it has to be rebuilt. The vector version brings:

d=c(as.Date('2010/01/01'), as.Date('2010/01/31'))
[1] "2010-02-01" "2010-03-03"

Hope you liked it))

Equivalent of varchar(max) in MySQL?

Mysql Converting column from VARCHAR to TEXT when under limit size!!!

mysql> CREATE TABLE varchars1(ch3 varchar(6),ch1 varchar(3),ch varchar(4000000))
Query OK, 0 rows affected, 1 warning (0.00 sec)

| Level | Code | Message                                     |
| Note  | 1246 | Converting column 'ch' from VARCHAR to TEXT |
1 row in set (0.00 sec)


Is there a "do ... while" loop in Ruby?

I found the following snippet while reading the source for Tempfile#initialize in the Ruby core library:

  tmpname = File.join(tmpdir, make_tmpname(basename, n))
  lock = tmpname + '.lock'
  n += 1
end while @@cleanlist.include?(tmpname) or
  File.exist?(lock) or File.exist?(tmpname)

At first glance, I assumed the while modifier would be evaluated before the contents of begin...end, but that is not the case. Observe:

>> begin
?>   puts "do {} while ()" 
>> end while false
do {} while ()
=> nil

As you would expect, the loop will continue to execute while the modifier is true.

>> n = 3
=> 3
>> begin
?>   puts n
>>   n -= 1
>> end while n > 0
=> nil

While I would be happy to never see this idiom again, begin...end is quite powerful. The following is a common idiom to memoize a one-liner method with no params:

def expensive
  @expensive ||= 2 + 2

Here is an ugly, but quick way to memoize something more complex:

def expensive
  @expensive ||=
      n = 99
      buf = "" 
        buf << "#{n} bottles of beer on the wall\n" 
        # ...
        n -= 1
      end while n > 0
      buf << "no more bottles of beer" 

Originally written by Jeremy Voorhis. The content has been copied here because it seems to have been taken down from the originating site. Copies can also be found in the Web Archive and at Ruby Buzz Forum. -Bill the Lizard

Spring Boot - Loading Initial Data

You can simply create a import.sql file in src/main/resources and Hibernate will execute it when the schema is created.

Java: how to use UrlConnection to post request with authorization?

To do oAuth authentication to external app (INSTAGRAM) Step 3 "get the token after receiving the code" Only code below worked for me

Worth to state also that it worked for me using some localhost URL with a callback servlet configured with name "callback in web.xml and callback URL registered: e.g. localhost:8084/MyAPP/docs/insta/callback

BUT after successfully completed authentication steps, using same external site "INSTAGRAM" to do GET of Tags or MEDIA to retrieve JSON data using initial method didn't work. Inside my servlet to do GET using url like e.g. only method found HERE worked

Thanks to all contributors

        URL url = new URL(httpurl);
        HashMap<String, String> params = new HashMap<String, String>();
        params.put("client_id", id);
        params.put("client_secret", secret);
        params.put("grant_type", "authorization_code");
        params.put("redirect_uri", redirect);
        params.put("code", code);  // your INSTAGRAM code received 
        Set set = params.entrySet();
        Iterator i = set.iterator();
        StringBuilder postData = new StringBuilder();
        for (Map.Entry<String, String> param : params.entrySet()) {
            if (postData.length() != 0) {
            postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
            postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
        byte[] postDataBytes = postData.toString().getBytes("UTF-8");

        HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
        conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
        BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
        StringBuilder builder = new StringBuilder();
        for (String line = null; (line = reader.readLine()) != null;) {
        System.out.println("INSTAGRAM token returned: "+builder.toString());

In PANDAS, how to get the index of a known value?

To get the index by value, simply add .index[0] to the end of a query. This will return the index of the first row of the result...

So, applied to your dataframe:

In [1]: a[a['c2'] == 1].index[0]     In [2]: a[a['c1'] > 7].index[0]   
Out[1]: 0                            Out[2]: 4                         

Where the query returns more than one row, the additional index results can be accessed by specifying the desired index, e.g. .index[n]

In [3]: a[a['c2'] >= 7].index[1]     In [4]: a[(a['c2'] > 1) & (a['c1'] < 8)].index[2]  
Out[3]: 4                            Out[4]: 3 

How to represent the double quotes character (") in regex?

you need to use backslash before ". like \"

From the doc here you can see that

A character preceded by a backslash ( \ ) is an escape sequence and has special meaning to the compiler.

and " (double quote) is a escacpe sequence

When an escape sequence is encountered in a print statement, the compiler interprets it accordingly. For example, if you want to put quotes within quotes you must use the escape sequence, \", on the interior quotes. To print the sentence

She said "Hello!" to me.

you would write

System.out.println("She said \"Hello!\" to me.");

Appending a byte[] to the end of another byte[]

You need to declare out as a byte array with a length equal to the lengths of ciphertext and mac added together, and then copy ciphertext over the beginning of out and mac over the end, using arraycopy.

byte[] concatenateByteArrays(byte[] a, byte[] b) {
    byte[] result = new byte[a.length + b.length]; 
    System.arraycopy(a, 0, result, 0, a.length); 
    System.arraycopy(b, 0, result, a.length, b.length); 
    return result;

CMake is not able to find BOOST libraries

Thanks Paul-g for your advise. For my part it was a bit different.

I installed Boost by following the Step 5 of :

And then I add PATH directory in the "FindBoos.cmake", located in /usr/local/share/cmake-3.5/Modules :

SET (BOOST_ROOT "../boost_1_60_0")
SET (BOOST_INCLUDEDIR "../boost_1_60_0/boost")
SET (BOOST_LIBRARYDIR "../boost_1_60_0/libs")


Exporting PDF with jspdf not rendering CSS

Slight change to @rejesh-yadav wonderful answer.

html2canvas now returns a promise.

html2canvas(document.body).then(function (canvas) {
    var img = canvas.toDataURL("image/png");
    var doc = new jsPDF();
    doc.addImage(img, 'JPEG', 10, 10);'test.pdf');        

Hope this helps some!

Store query result in a variable using in PL/pgSQL

I think you're looking for SELECT INTO:

select into name from test_table where id = x;

That will pull the name from test_table where id is your function's argument and leave it in the name variable. Don't leave out the table name prefix on or you'll get complaints about an ambiguous reference.

How to resolve the error "Unable to access jarfile ApacheJMeter.jar errorlevel=1" while initiating Jmeter?

If you'll go through these steps:

  1. In the Terminal type brew install jmeter and hit Enter
  2. When it'll be done type jmeter and hit Enter again

You won't have to solve any kind of issue. Don't thank

Datetime BETWEEN statement not working in SQL Server

Does the second query return any results from the 17th, or just from the 18th?

The first query will only return results from the 17th, or midnight on the 18th.

Try this instead

select * 
from LOGS 
where check_in >= CONVERT(datetime,'2013-10-17') 
and check_in< CONVERT(datetime,'2013-10-19')

"dd/mm/yyyy" date format in excel through vba

I got it

Cells(1, 1).Value = StartDate
Cells(1, 1).NumberFormat = "dd/mm/yyyy"

Basically, I need to set the cell format, instead of setting the date.

Closing Application with Exit button

You cannot exit your application. Using android.finish() won't exit the application, it just kills the activity. It's used when we don't want to see the previous activity on back button click. The application automatically exits when you switch off the device. The Android architecture does not support exiting the app. If you want, you can forcefully exit the app, but that's not considered good practice.

"SetPropertiesRule" warning message when starting Tomcat from Eclipse

Servers tab

--> doubleclick servername

--> Server Options: tick "Publish module contexts to separate XML files"

restart your server

How to find if a given key exists in a C++ std::map

template <typename T, typename Key>
bool key_exists(const T& container, const Key& key)
    return (container.find(key) != std::end(container));

Of course if you wanted to get fancier you could always template out a function that also took a found function and a not found function, something like this:

template <typename T, typename Key, typename FoundFunction, typename NotFoundFunction>
void find_and_execute(const T& container, const Key& key, FoundFunction found_function, NotFoundFunction not_found_function)
    auto& it = container.find(key);
    if (it != std::end(container))
        found_function(key, it->second);

And use it like this:

    std::map<int, int> some_map;
    find_and_execute(some_map, 1,
        [](int key, int value){ std::cout << "key " << key << " found, value: " << value << std::endl; },
        [](int key){ std::cout << "key " << key << " not found" << std::endl; });

The downside to this is coming up with a good name, "find_and_execute" is awkward and I can't come up with anything better off the top of my head...

Setting format and value in input type="date"

@cOnstructOr provided a great idea, but it left a comma in place

var today = new Date().toLocaleString('en-GB').split(' ')[0].slice(0,-1).split('/').reverse().join('-');

fixes that

How to achieve ripple animation using support library?

Basic ripple setup

  • Ripples contained within the view.

  • Ripples that extend beyond the view's bounds:

    Have a look here for resolving ?(attr) xml references in Java code.

Support Library

  • Using ?attr: (or the ? shorthand) instead of ?android:attr references the support library, so is available back to API 7.

Ripples with images/backgrounds

  • To have a image or background and overlaying ripple the easiest solution is to wrap the View in a FrameLayout with the ripple set with setForeground() or setBackground().

Honestly there is no clean way of doing this otherwise.

html5 audio player - jquery toggle click play/pause?

The reason why your attempt didn't work out is, that you have used a class-selector, which returns a collection of elements, not an (=one!) element, which you need to access the players properties and methods. To make it work there's basically three ways, which have been mentioned, but just for an overview:

Get the element – not a collection – by...

  • Iterating over the colllection and fetching the element with this (like in the accepted answer).

  • Using an id-selector, if available.

  • Getting the element of a collection, by fetching it, via its position in the collection by appending [0] to the selector, which returns the first element of the collection.

How to detect string which contains only spaces?

  console.log('string is empty or only contains spaces');

Removing the whitespace from a string can be done using String#trim().

To check if a string is null or undefined, one can check if the string itself is falsey, in which case it is null, undefined, or an empty string. This first check is necessary, as attempting to invoke methods on null or undefined will result in an error. To check if it contains only spaces, one can check if the string is falsey after trimming, which means that it is an empty string at that point.

if(!str || !str.trim()){
   //str is null, undefined, or contains only spaces

This can be simplified using the optional chaining operator.

   //str is null, undefined, or contains only spaces

If you are certain that the variable will be a string, only the second check is necessary.

   console.log("str is empty or contains only spaces");

How to call multiple functions with @click in vue?

This simple way to do v-on:click="firstFunction(); secondFunction();"

How to append to the end of an empty list?

use my_list.append(...) and do not use and other list to append as list are mutable.

Get week day name from a given month, day and year individually in SQL Server

Tested and works on SQL 2005 and 2008. Not sure if this works in 2012 and later.

The solution uses DATENAME instead of DATEPART

select datename(dw,getdate()) --Thursday
select datepart(dw,getdate()) --2

This is work in sql 2014 also.

SecurityError: The operation is insecure - window.history.pushState()

In my case I was missing 'www.' from the url I was pushing. It must be exact match, if you're working on, you must push to and not

Vue.js get selected option on @change

You can also use v-model for the rescue

    <select name="LeaveType" v-model="leaveType" @change="onChange()" class="form-control">
         <option value="1">Annual Leave/ Off-Day</option>
         <option value="2">On Demand Leave</option>

export default {
    data() {
        return {
            leaveType: '',

    methods: {
        onChange() {
            console.log('The new value is: ', this.leaveType)

Convert MFC CString to integer

You may use the C atoi function ( in a try / catch clause because the conversion isn't always possible) But there's nothing in the MFC classes to do it better.

CardView not showing Shadow in Android L

In my case the shadow was not showing on Android L devices because I did not add a margin. The problem is that the CardView creates this margin automatically on <5 devices so now I do it like this:

CardView card = new CardView(context);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
        LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    params.setMargins(shadowSize, shadowSize, shadowSize,
} else {

All ASP.NET Web API controllers return 404

Had essentially the same problem, solved in my case by adding:

<modules runAllManagedModulesForAllRequests="true" />

to the



section of web.config

heroku - how to see all the logs

Logging has greatly improved in heroku!

$ heroku logs -n 500


$ heroku logs --tail



These are no longer add-ons, but part of the default functionality :)

When are static variables initialized?

The static variable can be intialize in the following three ways as follow choose any one you like

  1. you can intialize it at the time of declaration
  2. or you can do by making static block eg:

    static {
            // whatever code is needed for initialization goes here
  3. There is an alternative to static blocks — you can write a private static method

    class name {
        public static varType myVar = initializeVar();
        private static varType initializeVar() {
            // initialization code goes here

How to deal with floating point number precision in JavaScript?


var x = 0.1*0.2;
 x =Math.round(x*Math.pow(10,2))/Math.pow(10,2);

Difference between static and shared libraries?

Static libraries are compiled as part of an application, whereas shared libraries are not. When you distribute an application that depends on shared libaries, the libraries, eg. dll's on MS Windows need to be installed.

The advantage of static libraries is that there are no dependencies required for the user running the application - e.g. they don't have to upgrade their DLL of whatever. The disadvantage is that your application is larger in size because you are shipping it with all the libraries it needs.

As well as leading to smaller applications, shared libraries offer the user the ability to use their own, perhaps better version of the libraries rather than relying on one that's part of the application

C# DataTable.Select() - How do I format the filter criteria to include null?

The way to check for null is to check for it:

DataRow[] myResultSet = myDataTable.Select("[COLUMN NAME] is null");

You can use and and or in the Select statement.

Docker remove <none> TAG images

To remove dangling images please use :

docker image rm $(docker images --format "{{.ID}}" --filter "dangling=true")

Please refer to my answer here for a more detailed description :

How to mock void methods with Mockito

The solution of so-called problem is to use a spy Mockito.spy(...) instead of a mock Mockito.mock(..).

Spy enables us to partial mocking. Mockito is good at this matter. Because you have class which is not complete, in this way you mock some required place in this class.

PHP with MySQL 8.0+ error: The server requested authentication method unknown to the client

@mohammed, this is usually attributed to the authentication plugin that your mysql database is using.

By default and for some reason, mysql 8 default plugin is auth_socket. Applications will most times expect to log in to your database using a password.

If you have not yet already changed your mysql default authentication plugin, you can do so by:
1. Log in as root to mysql
2. Run this sql command:

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password
BY 'password';  

Replace 'password' with your root password. In case your application does not log in to your database with the root user, replace the 'root' user in the above command with the user that your application uses.

Digital ocean expounds some more on this here Installing Mysql

Entity Framework: There is already an open DataReader associated with this Command

It is not about closing connection. EF manages connection correctly. My understanding of this problem is that there are multiple data retrieval commands executed on single connection (or single command with multiple selects) while next DataReader is executed before first one has completed the reading. The only way to avoid the exception is to allow multiple nested DataReaders = turn on MultipleActiveResultSets. Another scenario when this always happens is when you iterate through result of the query (IQueryable) and you will trigger lazy loading for loaded entity inside the iteration.

What is the difference between a database and a data warehouse?

Example: A house is worth $100,000, and it is appreciating at $1000 per year.

To keep track of the current house value, you would use a database as the value would change every year.

Three years later, you would be able to see the value of the house which is $103,000.

To keep track of the historical house value, you would use a data warehouse as the value of the house should be

$100,000 on year 0, 
$101,000 on year 1, 
$102,000 on year 2, 
$103,000 on year 3. 

Android getActivity() is undefined

This is because you're using getActivity() inside an inner class. Try using:


instead, though there's really no need for the getActivity() part. In your case, SherlockFragmentActivity .this should suffice.

Changing background colour of tr element on mouseover

You can give the tr an id and do it.

    background-color: green;
    cursor: pointer;
    height: 30px;


    background-color: blue;
    cursor: pointer;


<table width="400px">
<tr id="element">

Could not locate Gemfile

You do not have Gemfile in a directory where you run that command. Gemfile is a file containing your gem settings for a current program.

How do you create nested dict in Python?

It is important to remember when using defaultdict and similar nested dict modules such as nested_dict, that looking up a nonexistent key may inadvertently create a new key entry in the dict and cause a lot of havoc.

Here is a Python3 example with nested_dict module:

import nested_dict as nd
nest = nd.nested_dict()
nest['outer1']['inner1'] = 'v11'
nest['outer1']['inner2'] = 'v12'
print('original nested dict: \n', nest)
except KeyError as e:
    print('exception missing key', e)
print('nested dict after lookup with missing key.  no exception raised:\n', nest)

# Instead, convert back to normal dict...
nest_d = nest.to_dict(nest)
    print('converted to normal dict. Trying to lookup Wrong_key2')
except KeyError as e:
    print('exception missing key', e)
    print(' no exception raised:\n')

# ...or use dict.keys to check if key in nested dict
print('checking with dict.keys')
if 'wrong_key3' in list(nest.keys()):

    print('found wrong_key3')
    print(' did not find wrong_key3')

Output is:

original nested dict:   {"outer1": {"inner2": "v12", "inner1": "v11"}}

nested dict after lookup with missing key.  no exception raised:  
{"outer1": {"wrong_key1": {}, "inner2": "v12", "inner1": "v11"}} 

converted to normal dict. 
Trying to lookup Wrong_key2 

exception missing key 'wrong_key2' 

checking with dict.keys 

['wrong_key1', 'inner2', 'inner1']  
did not find wrong_key3

413 Request Entity Too Large - File Upload Issue

First edit the Nginx configuration file (nginx.conf)

Location: sudo nano /etc/nginx/nginx.conf

Add following codes:

http {
        client_max_body_size 100M;

Then Add the following lines in PHP configuration file(php.ini)

Location: sudo gedit /etc/php5/fpm/php.ini

Add following codes:

memory_limit = 128M 
post_max_size = 20M  
upload_max_filesize = 10M

Can a foreign key be NULL and/or duplicate?

Here's an example using Oracle syntax:
First let's create a table COUNTRY


Create the table PROVINCE


This runs perfectly fine in Oracle. Notice the COUNTRY_ID foreign key in the second table doesn't have "NOT NULL".

Now to insert a row into the PROVINCE table, it's sufficient to only specify the PROVINCE_ID. However, if you chose to specify a COUNTRY_ID as well, it must exist already in the COUNTRY table.

SQL Case Expression Syntax?

Oracle syntax from the 11g Documentation:

CASE { simple_case_expression | searched_case_expression }
     [ else_clause ]


expr { WHEN comparison_expr THEN return_expr }...


{ WHEN condition THEN return_expr }...


ELSE else_expr

How to use Git and Dropbox together?

Now in 2014, I have been using Git and Dropbox for about one year and a half without problem. Some points though:

  • All my machines using Dropbox are on Windows, different versions (7 to 8) + 1 mac.
  • I do not share the repository with someone else, so I am the only one to modify it.
  • git push pushes to a remote repository, so that if it ever gets corrupted, I can easily recover it.
  • I had to create aliases in C:\Users with mklink /D link target because some libraries were pointed to absolute locations.

How can I install pip on Windows?

How to install pip:

  1. Download and install ActivePython
  2. Open a command prompt (CMD)
  3. Type pypm install pip

Android Studio was unable to find a valid Jvm (Related to MAC OS)

I had previously uninstall Java 6 and install Java 7, Android Studio was working okay, then I upgraded Android Studio and I had the issue everyone is having. Today, I uninstalled Java 7 and installed Java 8 from Oracle. Then I uninstall Android Studio and installed the latest. Everything is working for me now

notifyDataSetChanged example

I had the same problem and I prefer not to replace the entire ArrayAdapter with a new instance continuously. Thus I have the AdapterHelper do the heavy lifting somewhere else.

Add this where you would normally (try to) call notify

new AdapterHelper().update((ArrayAdapter)adapter, new ArrayList<Object>(yourArrayList));

AdapterHelper class

public class AdapterHelper {
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public void update(ArrayAdapter arrayAdapter, ArrayList<Object> listOfObject){
        for (Object object : listOfObject){

SQL query for a carriage return in a string and ultimately removing carriage return

Something like this seems to work for me:

SELECT * FROM Parameters WHERE Name LIKE '%\n%'

Eloquent: find() and where() usage laravel

Your code looks fine, but there are a couple of things to be aware of:

Post::find($id); acts upon the primary key, if you have set your primary key in your model to something other than id by doing:

protected  $primaryKey = 'slug';

then find will search by that key instead.

Laravel also expects the id to be an integer, if you are using something other than an integer (such as a string) you need to set the incrementing property on your model to false:

public $incrementing = false;

Check if a specific value exists at a specific key in any subarray of a multidimensional array

If you have to make a lot of "id" lookups and it should be really fast you should use a second array containing all the "ids" as keys:


foreach($my_array as $arr){

Now you can check for an existing id very fast, for example:

echo (isset($lookup_array[152]))?'yes':'no';

jquery 3.0 url.indexOf error

Update all your code that calls load function like,

$(window).load(function() { ... });


$(window).on('load', function() { ... });

jquery.js:9612 Uncaught TypeError: url.indexOf is not a function

This error message comes from jQuery.fn.load function.

I've come across the same issue on my application. After some digging, I found this statement in jQuery blog,

.load, .unload, and .error, deprecated since jQuery 1.8, are no more. Use .on() to register listeners.

I simply just change how my jQuery objects call the load function like above. And everything works as expected.

Hide options in a select list using jQuery

 $('#id').val($('#id option:eq(0)').hide());

option:eq(0)-hide option at index '0' in select box.

How to join entries in a set into one string?

The join is called on the string:

print ", ".join(set_3)

Is Django for the frontend or backend?


Django is a framework, not a language. Python is the language in which Django is written.

Django is a collection of Python libs allowing you to quickly and efficiently create a quality Web application, and is suitable for both frontend and backend.

However, Django is pretty famous for its "Django admin", an auto generated backend that allows you to manage your website in a blink for a lot of simple use cases without having to code much.

More precisely, for the front end, Django helps you with data selection, formatting, and display. It features URL management, a templating language, authentication mechanisms, cache hooks, and various navigation tools such as paginators.

For the backend, Django comes with an ORM that lets you manipulate your data source with ease, forms (an HTML independent implementation) to process user input and validate data and signals, and an implementation of the observer pattern. Plus a tons of use-case specific nifty little tools.

For the rest of the backend work Django doesn't help with, you just use regular Python. Business logic is a pretty broad term.

You probably want to know as well that Django comes with the concept of apps, a self contained pluggable Django library that solves a problem. The Django community is huge, and so there are numerous apps that do specific business logic that vanilla Django doesn't.

Left Join With Where Clause

You might find it easier to understand by using a simple subquery

SELECT `settings`.*, (
    SELECT `value` FROM `character_settings`
    WHERE `character_settings`.`setting_id` = `settings`.`id`
      AND `character_settings`.`character_id` = '1') AS cv_value
FROM `settings`

The subquery is allowed to return null, so you don't have to worry about JOIN/WHERE in the main query.

Sometimes, this works faster in MySQL, but compare it against the LEFT JOIN form to see what works best for you.

SELECT s.*, c.value
FROM settings s
LEFT JOIN character_settings c ON c.setting_id = AND c.character_id = '1'

Most efficient way to concatenate strings?

Rico Mariani, the .NET Performance guru, had an article on this very subject. It's not as simple as one might suspect. The basic advice is this:

If your pattern looks like:

x = f1(...) + f2(...) + f3(...) + f4(...)

that's one concat and it's zippy, StringBuilder probably won't help.

If your pattern looks like:

if (...) x += f1(...)
if (...) x += f2(...)
if (...) x += f3(...)
if (...) x += f4(...)

then you probably want StringBuilder.

Yet another article to support this claim comes from Eric Lippert where he describes the optimizations performed on one line + concatenations in a detailed manner.

HighCharts Hide Series Name from the Legend

Set showInLegend to false.

series: [{
            showInLegend: false,
            name: 'Series',
            data: value                


Aside from @Verhás István answer (which I like), I was expecting a one-liner for the question:

${project.reporting.outputDirectory} resolves to target/site in your project.

SQL Server 2008 - Case / If statements in SELECT Clause

You are looking for the CASE statement

Example copied from MSDN:

USE AdventureWorks;
SELECT   ProductNumber, Category =
      CASE ProductLine
         WHEN 'R' THEN 'Road'
         WHEN 'M' THEN 'Mountain'
         WHEN 'T' THEN 'Touring'
         WHEN 'S' THEN 'Other sale items'
         ELSE 'Not for sale'
FROM Production.Product
ORDER BY ProductNumber;

Find provisioning profile in Xcode 5

It is not exactly for Xcode5 but this question links people who want to check where are provisioning profiles:
Following documentation

  1. Choose Xcode > Preferences.
  2. Click Accounts at the top of the window.
  3. Select the team you want to view, and click View Details. enter image description here In the dialog that appears, view your signing identities and provisioning profiles. If a Create button appears next to a certificate, it hasn’t been created yet. If a Download button appears next to a provisioning profile, it’s not on your Mac. enter image description here

Ten you can start context menu on each profile and click "Show in Finder" or "Move to Trash".

Can an abstract class have a constructor?

Yes it can, abstract classes constructors are generally used for super calls for initialization events common to all the subclasses

check if command was successful in a batch file

Most commands/programs return a 0 on success and some other value, called errorlevel, to signal an error.

You can check for this in you batch for example by:

if %ERRORLEVEL% == 0 goto :next
echo "Errors encountered during execution.  Exited with status: %errorlevel%"
goto :endofscript

echo "Doing the next thing"

echo "Script complete"

Adb Devices can't find my phone

I have a ZTE Crescent phone (Orange San Francisco II).

When I connect the phone to the USB a disk shows up in OS X named 'ZTE_USB_Driver'.

Running adb devices displays no connected devices. But after I eject the 'ZTE_USB_Driver' disk from OS X, and run adb devices again the phone shows up as connected.

'\r': command not found - .bashrc / .bash_profile

As per this gist, the solution is to create a ~/.bash_profile (in HOME directory) that contains:

set -o igncr

Internet Explorer 11 disable "display intranet sites in compatibility view" via meta tag not working

The marked answer is the correct one. However, Pricey, you should follow up on this with your AD and desktop admin groups. They are misusing the IE11 Enterprise Mode site list. Microsoft does NOT intend it to be used for all intranet sites within an organization at all. That would be propagating the existing "render all intranet sites in compatibility mode" setting that is the bane of corporate website advancement the world over.

It's meant to implemented as a "Black list", with the handful of sites that actually require a legacy browser mode listed in the Enterprise Mode list with their rendering requirements specified. All other sites in your organization are then freed up to use Edge. The people in your organization who implemented it with all intranet sites included to start with have completely misunderstood how Enterprise Mode is meant to be implemented.

How to extract table as text from the PDF using Python?

  • I would suggest you to extract the table using tabula.
  • Pass your pdf as an argument to the tabula api and it will return you the table in the form of dataframe.
  • Each table in your pdf is returned as one dataframe.
  • The table will be returned in a list of dataframea, for working with dataframe you need pandas.

This is my code for extracting pdf.

import pandas as pd
import tabula
file = "filename.pdf"
path = 'enter your directory path here'  + file
df = tabula.read_pdf(path, pages = '1', multiple_tables = True)

Please refer to this repo of mine for more details.

AngularJS check if form is valid in controller

I have updated the controller to:

    function ($scope, $http, $location, Business, BusinessService, UserService, Photo) {
        $scope.$watch('createBusinessForm.$valid', function(newVal) {
            //$scope.valid = newVal;
            $scope.informationStatus = true;

How to call a parent class function from derived class function?

In MSVC there is a Microsoft specific keyword for that: __super

MSDN: Allows you to explicitly state that you are calling a base-class implementation for a function that you are overriding.

// deriv_super.cpp
// compile with: /c
struct B1 {
   void mf(int) {}

struct B2 {
   void mf(short) {}

   void mf(char) {}

struct D : B1, B2 {
   void mf(short) {
      __super::mf(1);   // Calls B1::mf(int)
      __super::mf('s');   // Calls B2::mf(char)

What is function overloading and overriding in php?

Function overloading occurs when you define the same function name twice (or more) using different set of parameters. For example:

class Addition {
  function compute($first, $second) {
    return $first+$second;

  function compute($first, $second, $third) {
    return $first+$second+$third;

In the example above, the function compute is overloaded with two different parameter signatures. *This is not yet supported in PHP. An alternative is to use optional arguments:

class Addition {
  function compute($first, $second, $third = 0) {
    return $first+$second+$third;

Function overriding occurs when you extend a class and rewrite a function which existed in the parent class:

class Substraction extends Addition {
  function compute($first, $second, $third = 0) {
    return $first-$second-$third;

For example, compute overrides the behavior set forth in Addition.

How to replace all occurrences of a string in Javascript?

For the sake of completeness, I got to thinking about which method I should use to do this. There are basically two ways to do this as suggested by the other answers on this page.

Note: In general, extending the built-in prototypes in JavaScript is generally not recommended. I am providing as extensions on the String prototype simply for purposes of illustration, showing different implementations of a hypothetical standard method on the String built-in prototype.

Regular Expression Based Implementation

String.prototype.replaceAll = function(search, replacement) {
    var target = this;
    return target.replace(new RegExp(search, 'g'), replacement);

Split and Join (Functional) Implementation

String.prototype.replaceAll = function(search, replacement) {
    var target = this;
    return target.split(search).join(replacement);

Not knowing too much about how regular expressions work behind the scenes in terms of efficiency, I tended to lean toward the split and join implementation in the past without thinking about performance. When I did wonder which was more efficient, and by what margin, I used it as an excuse to find out.

On my Chrome Windows 8 machine, the regular expression based implementation is the fastest, with the split and join implementation being 53% slower. Meaning the regular expressions are twice as fast for the lorem ipsum input I used.

Check out this benchmark running these two implementations against each other.

As noted in the comment below by @ThomasLeduc and others, there could be an issue with the regular expression-based implementation if search contains certain characters which are reserved as special characters in regular expressions. The implementation assumes that the caller will escape the string beforehand or will only pass strings that are without the characters in the table in Regular Expressions (MDN).

MDN also provides an implementation to escape our strings. It would be nice if this was also standardized as RegExp.escape(str), but alas, it does not exist:

function escapeRegExp(str) {
  return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"); // $& means the whole matched string

We could call escapeRegExp within our String.prototype.replaceAll implementation, however, I'm not sure how much this will affect the performance (potentially even for strings for which the escape is not needed, like all alphanumeric strings).

What's the difference between a word and byte?

It seems all the answers assume high level languages and mainly C/C++.

But the question is tagged "assembly" and in all assemblers I know (for 8bit, 16bit, 32bit and 64bit CPUs), the definitions are much more clear:

byte  = 8 bits 
word  = 2 bytes
dword = 4 bytes = 2Words (dword means "double word")
qword = 8 bytes = 2Dwords = 4Words ("quadruple word")

Defining a variable with or without export

export NAME=value for settings and variables that have meaning to a subprocess.

NAME=value for temporary or loop variables private to the current shell process.

In more detail, export marks the variable name in the environment that copies to a subprocesses and their subprocesses upon creation. No name or value is ever copied back from the subprocess.

  • A common error is to place a space around the equal sign:

    $ export FOO = "bar"  
    bash: export: `=': not a valid identifier
  • Only the exported variable (B) is seen by the subprocess:

    $ A="Alice"; export B="Bob"; echo "echo A is \$A. B is \$B" | bash
    A is . B is Bob
  • Changes in the subprocess do not change the main shell:

    $ export B="Bob"; echo 'B="Banana"' | bash; echo $B
  • Variables marked for export have values copied when the subprocess is created:

    $ export B="Bob"; echo '(sleep 30; echo "Subprocess 1 has B=$B")' | bash &
    [1] 3306
    $ B="Banana"; echo '(sleep 30; echo "Subprocess 2 has B=$B")' | bash 
    Subprocess 1 has B=Bob
    Subprocess 2 has B=Banana
    [1]+  Done         echo '(sleep 30; echo "Subprocess 1 has B=$B")' | bash
  • Only exported variables become part of the environment (man environ):

     $ ALICE="Alice"; export BOB="Bob"; env | grep "ALICE\|BOB"

So, now it should be as clear as is the summer's sun! Thanks to Brain Agnew, alexp, and William Prusell.

How do I run a command on an already existing Docker container?

# docker exec -d container_id command 


# docker exec -d xcdefrdtt service jira stop 

Creating an empty file in C#

A somewhat common use case for creating an empty file is to trigger something else happening in a different process in the absence of more sophisticated in process communication. In this case, it can help to have the file creation be atomic from the outside world's point of view (particularly if the thing being triggered is going to delete the file to "consume" the trigger).

So it can help to create a junk name (Guid.NewGuid.ToString()) in the same directory as the file you want to create, and then do a File.Move from the temporary name to your desired name. Otherwise triggered code which checks for file existence and then deletes the trigger may run into race conditions where the file is deleted before it is fully closed out.

Having the temp file in the same directory (and file system) gives you the atomicity you may want. This gives something like.

public void CreateEmptyFile(string path)
    string tempFilePath = Path.Combine(Path.GetDirectoryName(path),
    using (File.Create(tempFilePath)) {}
    File.Move(tempFilePath, path);

JPA - Returning an auto generated id after persist()

This is how I did it:

EntityManager entityManager = getEntityManager();
EntityTransaction transaction = entityManager.getTransaction();
long id = object.getId();

Mipmap drawables for icons

There are two distinct uses of mipmaps:

  1. For launcher icons when building density specific APKs. Some developers build separate APKs for every density, to keep the APK size down. However some launchers (shipped with some devices, or available on the Play Store) use larger icon sizes than the standard 48dp. Launchers use getDrawableForDensity and scale down if needed, rather than up, so the icons are high quality. For example on an hdpi tablet the launcher might load the xhdpi icon. By placing your launcher icon in the mipmap-xhdpi directory, it will not be stripped the way a drawable-xhdpi directory is when building an APK for hdpi devices. If you're building a single APK for all devices, then this doesn't really matter as the launcher can access the drawable resources for the desired density.

  2. The actual mipmap API from 4.3. I haven't used this and am not familiar with it. It's not used by the Android Open Source Project launchers and I'm not aware of any other launcher using.

href="tel:" and mobile numbers

When dialing a number within the country you are in, you still need to dial the national trunk number before the rest of the number. For example, in Australia one would dial:

   0 - trunk prefix
   2 - Area code for New South Wales
6555 - STD code for a specific telephone exchange
1234 - Telephone Exchange specific extension.

For a mobile phone this becomes

   0 -      trunk prefix
   4 -      Area code for a mobile telephone
1234 5678 - Mobile telephone number

Now, when I want to dial via the international trunk, you need to drop the trunk prefix and replace it with the international dialing prefix

   + -      Short hand for the country trunk number
  61 -      Country code for Australia
   4 -      Area code for a mobile telephone
1234 5678 - Mobile telephone number

This is why you often find that the first digit of a telephone number is dropped when dialling internationally, even when using international prefixing to dial within the same country.

So as per the trunk prefix for Germany drop the 0 and add the +49 for Germany's international calling code (for example) giving:

<a href="tel:+496170961709" class="Blondie">_x000D_
    Call me, call me any, anytime_x000D_
      <b>Call me (call me) I'll arrive</b>_x000D_
        When you're ready we can share the wine!_x000D_

How do you disable viewport zooming on Mobile Safari?

In order to comply with WAI WCAG 2.0 AA accessibility requirements you must never disable pinch zoom. (WCAG 2.0: SC 1.4.4 Resize text Level AA). You can read more about it here: Mobile Accessibility: How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile, 2.2 Zoom/Magnification

How to do associative array/hashing in JavaScript

function HashTable() {
    this.length = 0;
    this.items = new Array();
    for (var i = 0; i < arguments.length; i += 2) {
        if (typeof (arguments[i + 1]) != 'undefined') {
            this.items[arguments[i]] = arguments[i + 1];

    this.removeItem = function (in_key) {
        var tmp_previous;
        if (typeof (this.items[in_key]) != 'undefined') {
            var tmp_previous = this.items[in_key];
            delete this.items[in_key];

        return tmp_previous;

    this.getItem = function (in_key) {
        return this.items[in_key];

    this.setItem = function (in_key, in_value) {
        var tmp_previous;
        if (typeof (in_value) != 'undefined') {
            if (typeof (this.items[in_key]) == 'undefined') {
            } else {
                tmp_previous = this.items[in_key];

            this.items[in_key] = in_value;

        return tmp_previous;

    this.hasItem = function (in_key) {
        return typeof (this.items[in_key]) != 'undefined';

    this.clear = function () {
        for (var i in this.items) {
            delete this.items[i];

        this.length = 0;

Get name of current script in Python

Note: If you are using Python 3+, then you should use the print() function instead

Assuming that the filename is, the below snippet

import sys
print sys.argv[0][:-3]


import sys
print sys.argv[0][::-1][3:][::-1]

As for other extentions with more characters, for example the filename foo.pypy

import sys
print sys.argv[0].split('.')[0]

If you want to extract from an absolute path

import sys
print sys.argv[0].split('/')[-1].split('.')[0]

will output foo

Easy pretty printing of floats in python?

A more permanent solution is to subclass float:

>>> class prettyfloat(float):
    def __repr__(self):
        return "%0.2f" % self

>>> x
[1.290192, 3.0002, 22.119199999999999, 3.4110999999999998]
>>> x = map(prettyfloat, x)
>>> x
[1.29, 3.00, 22.12, 3.41]
>>> y = x[2]
>>> y

The problem with subclassing float is that it breaks code that's explicitly looking for a variable's type. But so far as I can tell, that's the only problem with it. And a simple x = map(float, x) undoes the conversion to prettyfloat.

Tragically, you can't just monkey-patch float.__repr__, because float's immutable.

If you don't want to subclass float, but don't mind defining a function, map(f, x) is a lot more concise than [f(n) for n in x]

How do I compare two columns for equality in SQL Server?

What's wrong with CASE for this? In order to see the result, you'll need at least a byte, and that's what you get with a single character.


should work fine, and for all intents and purposes accomplishes the same thing as using a bit field.

Is it good practice to make the constructor throw an exception?

You do not need to throw a checked exception. This is a bug within the control of the program, so you want to throw an unchecked exception. Use one of the unchecked exceptions already provided by the Java language, such as IllegalArgumentException, IllegalStateException or NullPointerException.

You may also want to get rid of the setter. You've already provided a way to initiate age through the constructor. Does it need to be updated once instantiated? If not, skip the setter. A good rule, do not make things more public than necessary. Start with private or default, and secure your data with final. Now everyone knows that Person has been constructed properly, and is immutable. It can be used with confidence.

Most likely this is what you really need:

class Person { 

  private final int age;   

  Person(int age) {    

    if (age < 0) 
       throw new IllegalArgumentException("age less than zero: " + age); 

    this.age = age;   

  // setter removed

You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application

I was using a virtual environment on Ubuntu 18.04, and since I only wanted to install it as a client, I only had to do:

sudo apt install libpq-dev
pip install psycopg2

And installed without problems. Of course, you can use the binary as other answers said, but I preferred this solution since it was stated in a requirements.txt file.

HTML for the Pause symbol in audio and video control

▐▐  is HTML and is made with this code: &#9616;&#9616;.

Here's an example JSFiddle.

jQuery: How to get to a particular child of a parent?

Calling .parents(".box .something1") will return all parent elements that match the selector .box .something. In other words, it will return parent elements that are .something1 and are inside of .box.

You need to get the children of the closest parent, like this:


This code calls .closest to get the innermost parent matching a selector, then calls .children on that parent element to find the uncle you're looking for.

How to install PIP on Python 3.6?

Download python 3.6

It is possible that pip does not get installed by default. One potential fix is to open cmd and type:

python -m ensurepip --default-pip

and then

python -m pip install matplotlib

actually i had nothing in my scripts folder idk why but these steps worked for me.

Install Qt on Ubuntu

In Ubuntu 18.04 the QtCreator examples and API docs missing, This is my way to solve this problem, should apply to almost every Ubuntu release.

For QtCreator and Examples and API Docs:

sudo apt install `apt-cache search 5-examples | grep qt | grep example | awk '{print $1 }' | xargs `

sudo apt install `apt-cache search 5-doc | grep "Qt 5 " | awk '{print $1}' | xargs`

sudo apt-get install build-essential qtcreator qt5-default

If something is also missing, then:

sudo apt install `apt-cache search qt | grep 5- | grep ^qt | awk '{print $1}' | xargs `

Hope to be helpful.

Also posted in Ask Ubuntu:

Make 2 functions run at the same time

Try this

from threading import Thread

def fun1():
def fun2():

t1 = Thread(target=fun1)
t2 = Thread(target=fun2)


Fastest way to add an Item to an Array

It depends on how often you insert or read. You can increase the array by more than one if needed.

numberOfItems = ??

' ...

If numberOfItems+1 >= arr.Length Then
    Array.Resize(arr, arr.Length + 10)
End If

arr(numberOfItems) = newItem
numberOfItems += 1

Also for A, you only need to get the array if needed.

Dim list As List(Of Integer)(arr) ' Do this only once, keep a reference to the list
                                  ' If you create a new List everything you add an item then this will never be fast


arrayWasModified = True

' ...

Function GetArray()

    If arrayWasModified Then
        arr = list.ToArray()
    End If

    Return Arr
End Function

If you have the time, I suggest you convert it all to List and remove arrays.

* My code might not compile

How can I SELECT multiple columns within a CASE WHEN on SQL Server?

The problem is that the CASE statement won't work in the way you're trying to use it. You can only use it to switch the value of one field in a query. If I understand what you're trying to do, you might need this:

   FieldName = CASE 
                  WHEN ActivityTypeID <> 2 THEN
                      (Some Aggregate Sub Query)
                     (Some Aggregate Sub Query with diff result)
   FieldName2 = CASE
                  WHEN ActivityTypeID <> 2 THEN
                      (Some Aggregate Sub Query)
                     (Some Aggregate Sub Query with diff result)

How to build a 'release' APK in Android Studio?

AndroidStudio is alpha version for now. So you have to edit gradle build script files by yourself. Add next lines to your build.gradle

android {

    signingConfigs {

        release {

            storeFile file('android.keystore')
            storePassword "pwd"
            keyAlias "alias"
            keyPassword "pwd"

    buildTypes {

       release {

           signingConfig signingConfigs.release

To actually run your application at emulator or device run gradle installDebug or gradle installRelease.

You can create helloworld project from AndroidStudio wizard to see what structure of gradle files is needed. Or export gradle files from working eclipse project. Also this series of articles are helpfull

Moment get current date

Just call moment as a function without any arguments:


For timezone information with moment, look at the moment-timezone package:

How to get value from form field in django framework?

You can do this after you validate your data.

if myform.is_valid():
  data = myform.cleaned_data
  field = data['field']

Also, read the django docs. They are perfect.

iOS: present view controller programmatically

Here is how you can do it in Swift:

let vc = UIViewController()
self.presentViewController(vc, animated: true, completion: nil)

Convert array to JSON

The shortest way I know to generate valid json from array of integers is

let json = `[${cars}]`

for more general object/array use JSON.stringify(cars) (for object with circular references use this)

let cars = [1,2,3]; cars.push(4,5,6);

let json = `[${cars}]`;

console.log(JSON.parse(json)); // json validation

Peak-finding algorithm for Python/SciPy

To detect both positive and negative peaks, PeakDetect is helpful.

from peakdetect import peakdetect

peaks = peakdetect(data, lookahead=20) 
# Lookahead is the distance to look ahead from a peak to determine if it is the actual peak. 
# Change lookahead as necessary 
higherPeaks = np.array(peaks[0])
lowerPeaks = np.array(peaks[1])
plt.plot(higherPeaks[:,0], higherPeaks[:,1], 'ro')
plt.plot(lowerPeaks[:,0], lowerPeaks[:,1], 'ko')


Creating a PHP header/footer

You can use this for header: Important: Put the following on your PHP pages that you want to include the content.

//at top:
// at bottom:

You can also include a navbar globaly just use this instead:

 // At top:
// At bottom:
 //Wherever navbar goes:

In header.php:

 <!DOCTYPE html>
 <html lang="en">
    <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

Do Not close Body or Html tags!
Include html here:

 //Or more global php here:



Code here:




<p> Include html code here</p>
 //Include Navbar PHP code here


  • Cleaner main php file (index.php) script.
  • Change the header or footer. etc to change it on all pages with the include— Good for alerts on all pages etc...
  • Time Saving!
  • Faster page loads!
  • you can have as many files to include as needed!
  • server sided!

Converting data frame column from character to numeric

If we need only one column to be numeric

yyz$b <- as.numeric(as.character(yyz$b))

But, if all the columns needs to changed to numeric, use lapply to loop over the columns and convert to numeric by first converting it to character class as the columns were factor.

yyz[] <- lapply(yyz, function(x) as.numeric(as.character(x)))

Both the columns in the OP's post are factor because of the string "n/a". This could be easily avoided while reading the file using na.strings = "n/a" in the read.table/read.csv or if we are using data.frame, we can have character columns with stringsAsFactors=FALSE (the default is stringsAsFactors=TRUE)

Regarding the usage of apply, it converts the dataset to matrix and matrix can hold only a single class. To check the class, we need

lapply(yyz, class)


sapply(yyz, class)

Or check


Can't use modulus on doubles?

fmod(x, y) is the function you use.

How to convert a GUID to a string in C#?

Following Sonar rules, you should whenever you can try to protect yourself, and use System.globalisation whenever it's possible like for DateTime.ToString().

So regarding the other answers you could use:

guid.ToString("", CultureInfo.InvariantCulture)

where "" can be replaces by : N, D, B , P and X for more infos see this comment.

Example here

path.join vs path.resolve with __dirname

From the doc for path.resolve:

The resulting path is normalized and trailing slashes are removed unless the path is resolved to the root directory.

But path.join keeps trailing slashes


__dirname = '/';
path.resolve(__dirname, 'foo/'); // '/foo'
path.join(__dirname, 'foo/'); // '/foo/'

How to use youtube-dl from a python program?

I would like this

from subprocess import call

command = "youtube-dl -c"
call(command.split(), shell=False)

JSON parse error: Can not construct instance of java.time.LocalDate: no String-argument constructor/factory method to deserialize from String value

Well, what I do on every project is a mix of the options above.

First, add the jsr310 dependency:


Important detail: put this dependency on the top of your depedencies list. I already see a project where the Localdate error persists even with this dependency on the pom.xml. But changing the order of the depedency the error was gone.

On your /src/main/resources/application.yml file, setup the write-dates-as-timestamps property:

      write-dates-as-timestamps: false

And create a ObjectMapper bean as this:

public class WebConfigurer {

    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper =;
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        return objectMapper;


Following this configuration, the conversion always work on Spring Boot 1.5.x without any error.

Bonus: Spring AMQP Queue configuration

Working with Spring AMQP, pay attention if you have a new instance of Jackson2JsonMessageConverter (common thing when creating a SimpleRabbitListenerContainerFactory). You need to pass the ObjectMapper bean to it, like:

Jackson2JsonMessageConverter converter = new Jackson2JsonMessageConverter(objectMapper);

Otherwise, you will receive the same error.

The difference between sys.stdout.write and print?

It is preferable when dynamic printing is useful, for instance, to give information in a long process:

import time, sys
Iterations = 555
for k in range(Iterations+1):

    # Some code to execute here ...

    percentage = k / Iterations
    time_msg = "\rRunning Progress at {0:.2%} ".format(percentage)

Difference between os.getenv and os.environ.get

See this related thread. Basically, os.environ is found on import, and os.getenv is a wrapper to os.environ.get, at least in CPython.

EDIT: To respond to a comment, in CPython, os.getenv is basically a shortcut to os.environ.get ; since os.environ is loaded at import of os, and only then, the same holds for os.getenv.

How to fix: "UnicodeDecodeError: 'ascii' codec can't decode byte"

Here is my solution, just add the encoding. with open(file, encoding='utf8') as f

And because reading glove file will take a long time, I recommend to the glove file to a numpy file. When netx time you read the embedding weights, it will save your time.

import numpy as np
from tqdm import tqdm

def load_glove(file):
    """Loads GloVe vectors in numpy array.
        file (str): a path to a glove file.
        dict: a dict of numpy arrays.
    embeddings_index = {}
    with open(file, encoding='utf8') as f:
        for i, line in tqdm(enumerate(f)):
            values = line.split()
            word = ''.join(values[:-300])
            coefs = np.asarray(values[-300:], dtype='float32')
            embeddings_index[word] = coefs

    return embeddings_index

# EMBEDDING_PATH = '../embedding_weights/glove.840B.300d.txt'
EMBEDDING_PATH = 'glove.840B.300d.txt'
embeddings = load_glove(EMBEDDING_PATH)'glove_embeddings.npy', embeddings) 

Gist link:

How can you tell when a layout has been drawn?

An alternative to the usual methods is to hook into the drawing of the view.

OnPreDrawListener is called many times when displaying a view, so there is no specific iteration where your view has valid measured width or height. This requires that you continually verify (view.getMeasuredWidth() <= 0) or set a limit to the number of times you check for a measuredWidth greater than zero.

There is also a chance that the view will never be drawn, which may indicate other problems with your code.

final View view = [ACQUIRE REFERENCE]; // Must be declared final for inner class
ViewTreeObserver viewTreeObserver = view.getViewTreeObserver();
viewTreeObserver.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
    public boolean onPreDraw() {
        if (view.getMeasuredWidth() > 0) {     
            int width = view.getMeasuredWidth();
            int height = view.getMeasuredHeight();
            //Do something with width and height here!
        return true; // Continue with the draw pass, as not to stop it

Better techniques for trimming leading zeros in SQL Server?

SUBSTRING(str_col, PATINDEX('%[^0]%', str_col+'.'), LEN(str_col))

When does Java's Thread.sleep throw InterruptedException?

The Java Specialists newsletter (which I can unreservedly recommend) had an interesting article on this, and how to handle the InterruptedException. It's well worth reading and digesting.

Updating records codeigniter

In your Controller

public function updtitle() 
    $data = array(
        'table_name' => 'your_table_name_to_update', // pass the real table name
        'id' => $this->input->post('id'),
        'title' => $this->input->post('title')

    $this->load->model('Updmodel'); // load the model first
    if($this->Updmodel->upddata($data)) // call the method from the model
        // update successful
        // update not successful


In Your Model

public function upddata($data) {
    $this->db->where('emp_no', $id);
    $this->db->update($table_name, array('title' => $title));
    return true;

The active record query is similar to

"update $table_name set title='$title' where emp_no=$id"

Compare two files line by line and generate the difference in another file

Consider this:
file a.txt:


file b.txt:


You can find the difference with:

diff -a --suppress-common-lines -y a.txt b.txt

The output will be:


You can redirict the output in an output file (c.txt) using:

diff -a --suppress-common-lines -y a.txt b.txt > c.txt

This will answer your question:

"...which contains the lines in file1 which are not present in file2."

How to JSON serialize sets?

Only dictionaries, Lists and primitive object types (int, string, bool) are available in JSON.

psql: FATAL: Ident authentication failed for user "postgres"

You can set the environment variable PGHOST=localhost:

$ psql -U db_user db_name
psql: FATAL:  Peer authentication failed for user "db_user"

$ export PGHOST=localhost
$ psql -U db_user db_name

Password for user mfonline:

Laravel 5 Class 'form' not found

Use Form, not form. The capitalization counts.

Print a div using javascript in angularJS single page application

Two conditional functions are needed: one for Google Chrome, and a second for the remaining browsers.

$scope.printDiv = function (divName) {

    var printContents = document.getElementById(divName).innerHTML; 

    if (navigator.userAgent.toLowerCase().indexOf('chrome') > -1) {
        var popupWin ='', '_blank', 'width=600,height=600,scrollbars=no,menubar=no,toolbar=no,location=no,status=no,titlebar=no');
        popupWin.document.write('<!DOCTYPE html><html><head>' +
            '<link rel="stylesheet" type="text/css" href="style.css" />' +
            '</head><body onload="window.print()"><div class="reward-body">' + printContents + '</div></body></html>');
        popupWin.onbeforeunload = function (event) {
            return '.\n';
        popupWin.onabort = function (event) {
    } else {
        var popupWin ='', '_blank', 'width=800,height=600');;
        popupWin.document.write('<html><head><link rel="stylesheet" type="text/css" href="style.css" /></head><body onload="window.print()">' + printContents + '</body></html>');

    return true;

Comparing two input values in a form validation with AngularJS

Of course for very simple comparisons you can always use ngMin/ngMax.

Otherwise, you can go with a custom directive, and there is no need of doing any $watch or $observe or $eval or this fancy $setValidity back and forth. Also, there is no need to hook into the postLink function at all. Try to stay out of the DOM as much as possible, as it is against the angular spirit.

Just use the lifecycle hooks the framework gives you. Add a validator and $validate at each change. Simple as that.

app.directive('sameAs', function() {
  return {
    restrict: 'A',
    require: {
      ngModelCtrl: 'ngModel'
    scope: {
      reference: '<sameAs'
    bindToController: true,
    controller: function($scope) {
      var $ctrl = $scope.$ctrl;

      //add the validator to the ngModelController
      $ctrl.$onInit = function() {
        function sameAsReference (modelValue, viewValue) {
          if (!$ctrl.reference || !modelValue) { //nothing to compare
            return true;
          return modelValue === $ctrl.reference;
        $ctrl.ngModelCtrl.$validators.sameas = sameAsReference;

      //do the check at each change
      $ctrl.$onChanges = function(changesObj) {
    controllerAs: '$ctrl'

Your plunker.

Best way to change the background color for an NSView

Use NSBox, which is a subclass of NSView, allowing us to easily style

Swift 3

let box = NSBox()
box.boxType = .custom
box.fillColor =
box.cornerRadius = 5

How to disable all div content

Or just use css and a "disabled" class.
Note: don't use the disabled attribute.
No need to mess with jQuery on/off.
This is much easier and works cross browser:

    position: relative;
    content: "";
    position: absolute;
    width: 100%;
    height: inherit;
    background-color: rgba(0,0,0,0.1);
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;

Then you can shut it on and off when initializing your page, or toggling a button

if(myDiv !== "can be edited"){
} else{

UICollectionView - Horizontal scroll, horizontal layout?

for xcode 8 i did this and it worked:

What is the purpose of "pip install --user ..."?

Other answers mention site.USER_SITE as where Python packages get placed. If you're looking for binaries, these go in {site.USER_BASE}/bin.

If you want to add this directory to your shell's search path, use:

export PATH="${PATH}:$(python3 -c 'import site; print(site.USER_BASE)')/bin"

Ant: How to execute a command for each file in directory?

ant-contrib is evil; write a custom ant task.

ant-contrib is evil because it tries to convert ant from a declarative style to an imperative style. But xml makes a crap programming language.

By contrast a custom ant task allows you to write in a real language (Java), with a real IDE, where you can write unit tests to make sure you have the behavior you want, and then make a clean declaration in your build script about the behavior you want.

This rant only matters if you care about writing maintainable ant scripts. If you don't care about maintainability by all means do whatever works. :)


how to enable sqlite3 for php?

In Centos 6.7, in my case the library file /usr/lib64/php/modules/ was missing.

yum install php-pdo 

vim /etc/php.d/sqlite3.ini
; Enable sqlite3 extension module

sudo service httpd restart

Getting files by creation date in .NET

If the performance is an issue, you can use this command in MS_DOS:

dir /OD >d:\dir.txt

This command generate a dir.txt file in **d:** root the have all files sorted by date. And then read the file from your code. Also, you add other filters by * and ?.

Run JavaScript in Visual Studio Code

I would suggest you to use a simple and easy plugin called as Quokka which is very popular these days and helps you debug your code on the go. Quokka.js. One biggest advantage in using this plugin is that you save a lot of time to go on web browser and evaluate your code, with help of this you can see everything happening in VS code, which saves a lot of time.

Delete a database in phpMyAdmin

Taking a queue from michael's answer above, I was unable to find the DROP Database command on my phpMyAdmin console in the localhost.

Apparantly I was missing a setting. Go to file of the phpMyAdmin folder, and add this:

$cfg['AllowUserDropDatabase'] = true;

Save and restart the local server and the command appears inside the console.

jQuery - on change input text

That is working for me. Could be a browser issue as mentioned, or maybe jQuery isn't registered properly, or perhaps the real issue is more complicated (that you made a simpler version to ask this). PS - did have to click out of the text box to make it fire.

Getting Textbox value in Javascript

<script type="text/javascript" runat="server">
 public void Page_Load(object Sender, System.EventArgs e)
        double rad=0.0;
        TextBox1.Attributes.Add("Visible", "False");
        if (TextBox1.Text != "") 
        rad = Convert.ToDouble(TextBox1.Text);    
        Button1.Attributes.Add("OnClick","alert("+ rad +")");

<asp:Button ID="Button1" runat="server" Text="Diameter" 
            style="z-index: 1; left: 133px; top: 181px; position: absolute" />
<asp:TextBox ID="TextBox1" Visible="True" Text="" runat="server" 
            style="z-index: 1; left: 134px; top: 133px; position: absolute" ></asp:TextBox>

use the help of this, hope it will be usefull

Proper way to wait for one function to finish before continuing?

This what I came up with, since I need to run several operations in a chain.

<button onclick="tprom('Hello Niclas')">test promise</button>

    function tprom(mess) {

        var promise = new Promise(function (resolve, reject) {
            setTimeout(function () {
            }, 2000);

        var promise2 = new Promise(async function (resolve, reject) {
            await promise;
            setTimeout(function () {
                resolve(mess + ' ' + mess);
            }, 2000);

        var promise3 = new Promise(async function (resolve, reject) {
            await promise2;
            setTimeout(function () {
                resolve(mess + ' ' + mess+ ' ' + mess);
            }, 2000);

        promise.then(function (data) {

        promise2.then(function (data) {

        promise3.then(function (data) {


Change icons of checked and unchecked for Checkbox for Android

Kind of a mix:

Set it in your layout file :-

 <CheckBox android:layout_width="wrap_content"
           android:text="new checkbox"
           android:button="@drawable/checkbox" />

where the @drawable/checkbox will look like:

<?xml version="1.0" encoding="utf-8"?>

<selector xmlns:android="">
 <item android:state_checked="true" android:state_focused="true"
  android:drawable="@drawable/checkbox_on_background_focus_yellow" />
 <item android:state_checked="false" android:state_focused="true"
  android:drawable="@drawable/checkbox_off_background_focus_yellow" />
 <item android:state_checked="false"
  android:drawable="@drawable/checkbox_off_background" />
 <item android:state_checked="true"
  android:drawable="@drawable/checkbox_on_background" />

What is the use of static constructors?

1.It can only access the static member(s) of the class.

Reason : Non static member is specific to the object instance. If static constructor are allowed to work on non static members it will reflect the changes in all the object instance, which is impractical.

2.There should be no parameter(s) in static constructor.

Reason: Since, It is going to be called by CLR, nobody can pass the parameter to it. 3.Only one static constructor is allowed.

Reason: Overloading needs the two methods to be different in terms of method/constructor definition which is not possible in static constructor.

4.There should be no access modifier to it.

Reason: Again the reason is same call to static constructor is made by CLR and not by the object, no need to have access modifier to it

How do you create a foreign key relationship in a SQL Server CE (Compact Edition) Database?

Alan is correct when he says there's designer support. Rhywun is incorrect when he implies you cannot choose the foreign key table. What he means is that in the UI the foreign key table drop down is greyed out - all that means is he has not right clicked on the correct table to add the foreign key to.

In summary, right click on the foriegn key table and then via the 'Table Properties' > 'Add Relations' option you select the related primary key table.

I've done it numerous times and it works.

How to kill/stop a long SQL query immediately?

If you cancel and see that run

 sp_who2 'active'

(Activity Monitor won't be available on old sql server 2000 FYI )

Spot the SPID you wish to kill e.g. 81

Kill 81

Run the sp_who2 'active' again and you will probably notice it is sleeping ... rolling back

To get the STATUS run again the KILL

Kill 81 

Then you will get a message like this

 SPID 81: transaction rollback in progress. Estimated rollback completion: 63%. Estimated time remaining: 992 seconds.

Plotting images side by side using matplotlib

If the images are in an array and you want to iterate through each element and print it, you can write the code as follows:

plt.figure(figsize=(10,10)) # specifying the overall grid size

for i in range(25):
    plt.subplot(5,5,i+1)    # the number of images in the grid is 5*5 (25)

Also note that I used subplot and not subplots. They're both different

How to unstash only certain files?

For Windows users: curly braces have special meaning in PowerShell. You can either surround with single quotes or escape with backtick. For example:

git checkout 'stash@{0}' YourFile

Without it, you may receive an error:

Unknown switch 'e'

laravel 5 : Class 'input' not found

In first your problem is about the spelling of the input class, should be Input instead of input. And you have to import the class with the good namespace.

use Illuminate\Support\Facades\Input;

If you want it called 'input' not 'Input', add this :

use Illuminate\Support\Facades\Input as input;

Second, It's a dirty way to store into the database via route.php, and you're not processing data validation. If a sent parameter isn't what you expected, maybe an SQL error will appear, its caused by the data type. You should use controller to interact with information and store via the model in the controller method.

The route.php file handles routing. It is designed to make the link between the controller and the asked route.

To learn about controller, middleware, model, service ...

If you need some more information, solution about problem you can join the community :


Test a string for a substring

There are several other ways, besides using the in operator (easiest):


>>> try:
...   "xxxxABCDyyyy".index("test")
... except ValueError:
...   print "not found"
... else:
...   print "found"
not found


>>> if "xxxxABCDyyyy".find("ABCD") != -1:
...   print "found"


>>> import re
>>> if"ABCD" , "xxxxABCDyyyy"):
...  print "found"

pip install: Please check the permissions and owner of that directory

basic info

  • system: mac os 18.0.0
  • current user: yutou

the key

  1. add the current account to wheel group
sudo dscl . -append /Groups/wheel wheel $(whoami)
  1. modify python package mode to 775.
chmod -R 775 ${this_is_your_python_package_path}

the whole thing

  • when python3 compiled well, the infomation is just like the question said.
  • I try to use pip3 install requests and got:
File "/usr/local/python3/lib/python3.6/", line 220, in makedirs
    mkdir(name, mode)
PermissionError: [Errno 13] Permission denied: 
  • so i cd /usr/local/python3/lib/python3.6/site-packages, then ls -al and got:
drwxr-xr-x    6 root   wheel   192B  2 27 18:06 requests/

when i saw this, i understood, makedirs is an action of write, but the requests mode drwxrwxr-x displaied only user root can write the requests file. If add yutou(whoami) to the group wheel, and modify the package to the group wheel can write, then i can write, and the problem solved.

How to add yutou to group wheel? + detect group wheel, sudo dscl . -list /groups GroupMembership, you will find:

wheel                    root

the group wheel only one member root. + add yutou to group wheel, sudo dscl . -append /Groups/wheel wheel yutou. + check, sudo dscl . -list /groups GroupMembership:

wheel                    root yutou

modify the python package mode

chmod -R 775 /usr/local/python3/lib/python3.6

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

There are two types of string in python: the traditional str type and the newer unicode type. If you type a string literal without the u in front you get the old str type which stores 8-bit characters, and with the u in front you get the newer unicode type that can store any Unicode character.

The r doesn't change the type at all, it just changes how the string literal is interpreted. Without the r, backslashes are treated as escape characters. With the r, backslashes are treated as literal. Either way, the type is the same.

ur is of course a Unicode string where backslashes are literal backslashes, not part of escape codes.

You can try to convert a Unicode string to an old string using the str() function, but if there are any unicode characters that cannot be represented in the old string, you will get an exception. You could replace them with question marks first if you wish, but of course this would cause those characters to be unreadable. It is not recommended to use the str type if you want to correctly handle unicode characters.

Find control by name from Windows Forms controls

Use Control.ControlCollection.Find.

TextBox tbx = this.Controls.Find("textBox1", true).FirstOrDefault() as TextBox;
tbx.Text = "found!";

EDIT for asker:

Control[] tbxs = this.Controls.Find(txtbox_and_message[0,0], true);
if (tbxs != null && tbxs.Length > 0)
    tbxs[0].Text = "Found!";

How to fix C++ error: expected unqualified-id

Get rid of the semicolon after WordGame.

You really should have discovered this problem when the class was a lot smaller. When you're writing code, you should be compiling about every time you add half a dozen lines.

AngularJS error: 'argument 'FirstCtrl' is not a function, got undefined'

I am not sure about this tutorial but I had the same problem when I forgot to include the file into grunt/gulp minimization process.

  uglify: {
    my_target: {
      files: {
        'dest/output.min.js': ['src/input1.js', 'src/missing_controller.js']

Hope that helps.

How to check internet access on Android? InetAddress never times out

Just create the following class which checks for an internet connection:

public class ConnectionStatus {

    private Context _context;

    public ConnectionStatus(Context context) {
        this._context = context;

    public boolean isConnectionAvailable() {
        ConnectivityManager connectivity = (ConnectivityManager) _context
        if (connectivity != null) {
            NetworkInfo[] info = connectivity.getAllNetworkInfo();
            if (info != null)
                for (int i = 0; i < info.length; i++)
                    if (info[i].getState() == NetworkInfo.State.CONNECTED) {
                        return true;
        return false;

This class simply contains a method which returns the boolean value of the connection status. Therefore in simple terms, if the method finds a valid connection to the Internet, the return value is true, otherwise false if no valid connection is found.

The following method in the MainActivity then calls the result from the method previously described, and prompts the user to act accordingly:

public void addListenerOnWifiButton() {
        Button btnWifi = (Button)findViewById(;

        iia = new ConnectionStatus(getApplicationContext());

        isConnected = iia.isConnectionAvailable();
        if (!isConnected) {
            btnWifi.setOnClickListener(new View.OnClickListener() {

                public void onClick(View v) {
                    startActivity(new Intent(Settings.ACTION_WIFI_SETTINGS));
                    Toast.makeText(getBaseContext(), "Please connect to a hotspot",
        else {
            warning.setText("This app may use your mobile data to update events and get their details.");

In the above code, if the result is false, (therefore there is no internet connection, the user is taken to the Android wi-fi panel, where he is prompted to connect to a wi-fi hotspot.

How do you append to a file?

You can also do it with print instead of write:

with open('test.txt', 'a') as f:
    print('appended text', file=f)

If test.txt doesn't exist, it will be created...

Python - Check If Word Is In A String

What is wrong with:

if word in mystring: 
   print 'success'

How to serialize Joda DateTime with Jackson JSON processor?

Meanwhile Jackson registers the Joda module automatically when the JodaModule is in classpath. I just added jackson-datatype-joda to Maven and it worked instantly.


JSON output:

{"created" : "2017-03-28T05:59:27.258Z"}

How to tag an older commit in Git?


git tag -a v1.2 9fceb02 -m "Message here"

Where 9fceb02 is the beginning part of the commit id.

You can then push the tag using git push origin v1.2.

You can do git log to show all the commit id's in your current branch.

There is also a good chapter on tagging in the Pro Git book.

Warning: This creates tags with the current date (and that value is what will show on a GitHub releases page, for example). If you want the tag to be dated with the commit date, please look at another answer.

javascript Unable to get property 'value' of undefined or null reference

you have many HTML and java script mistakes includes: tag, using non UTF-8 encoding for form submission, no need,... You must use document.forms.FORMNAME or document.forms[0] for first appear form in page Corrected:

 function validate_frm_new_user_request()_x000D_
    var valid = true;_x000D_
    if ( document.forms.frm_new_user_request.u_userid.value == "" )_x000D_
        alert ( "Please enter your valid ISID Information." );_x000D_
        valid = false;_x000D_
  console.log("FALSE::Empty Value ");_x000D_
return valid;_x000D_
<html lang="en" xml:lang="en" xmlns="">_x000D_
    <meta content="text/html;charset=UTF-8" http-equiv="content-type" />_x000D_
<form method="post" action="" name="frm_new_user_request" id="frm_new_user_request" onsubmit="return validate_frm_new_user_request();">_x000D_
        <tr align="left">_x000D_
            <td><Label>ISID<em>*:</Label><input maxlength="15" id="u_userid" name="u_userid" size="20" type="text"/></td>_x000D_
            <td align="center" colspan="4">_x000D_
                <input type="image" src="btn.png" border="0" ALT="Create New Request">_x000D_

Run Stored Procedure in SQL Developer?

Creating Pl/SQL block can be painful if you have a lot of procedures which have a lot of parameters. There is an application written on python that do it for you. It parses the file with procedure declarations and creates the web app for convenient procedure invocations.

How to read all files in a folder from Java?

I think this is good way to read all the files in a folder and sub folder's

private static void addfiles (File input,ArrayList<File> files)
        ArrayList <File> path = new ArrayList<File>(Arrays.asList(input.listFiles()));
        for(int i=0 ; i<path.size();++i)

Check if string ends with one of the strings from a list

I have this:

def has_extension(filename, extension):

    ext = "." + extension
    if filename.endswith(ext):
        return True
        return False

How to fix the error; 'Error: Bootstrap tooltips require Tether ('

For webpack I resolved this with webpack.config.js:

new webpack.ProvidePlugin({
  $: 'jquery',
  jQuery: 'jquery',
  "window.jQuery": "jquery",
  Tether: 'tether'

How to add screenshot to READMEs in github repository?

To me the best way is -

  1. Create an new issue with that repository on github and then upload the file in gif format.To convert video files into gif format you can use this website
  2. Submit the newly created issue.
  3. Copy the address of the uploaded file
  4. Finally in your README file put ![demo](COPIED ADDRESS)

Hope this will help .

jQuery get value of selected radio button

Check the example it works fine

<div class="dtl_radio">
  Metal purity : 
    <input type="radio" name="purityradio" class="gold_color" value="92" checked="">
    92 %
    <input type="radio" name="purityradio" class="gold_color" value="75">
    75 %
    <input type="radio" name="purityradio" class="gold_color" value="58.5">
    58.5 %
    <input type="radio" name="purityradio" class="gold_color" value="95">
    95 %
    <input type="radio" name="purityradio" class="gold_color" value="59">
    59 %
    <input type="radio" name="purityradio" class="gold_color" value="76">
    76 %
    <input type="radio" name="purityradio" class="gold_color" value="93">
    93 %

var check_value = $('.gold_color:checked').val();

How to use Greek symbols in ggplot2?

You do not need the latex2exp package to do what you wanted to do. The following code would do the trick.

ggplot(smr, aes(Fuel.Rate, Eng.Speed.Ave., color=Eng.Speed.Max.)) + 
  geom_point() + 
  labs(title=expression("Fuel Efficiency"~(alpha*Omega)), 
color=expression(alpha*Omega), x=expression(Delta~price))

enter image description here

Also, some comments (unanswered as of this point) asked about putting an asterisk (*) after a Greek letter. expression(alpha~"*") works, so I suggest giving it a try.

More comments asked about getting ? Price and I find the most straightforward way to achieve that is expression(Delta~price)). If you need to add something before the Greek letter, you can also do this: expression(Indicative~Delta~price) which gets you:

enter image description here

200 PORT command successful. Consider using PASV. 425 Failed to establish connection

You need to use passive mode.

If you're using linux client, use pftp or ftp -p.

From man ftp:

-p    Use passive mode for data transfers. Allows use of ftp in environments where a firewall prevents connections from the outside world back to the client machine. Requires that the ftp server support the PASV command. This is the default if invoked as pftp.

rails bundle clean

If you are using RVM you can install your gems into gemsets. That way when you want to perform a full cleanup you can simply remove the gemset, which in turn removes all the gems installed in it. Your other option is to simply uninstall your unused gems and re-run your bundle install command.

Since bundler is meant to be a project-per-project gem versioning tool it does not provide a bundle clean command. Doing so would mean the possibility of removing gems associated with other projects as well, which would not be desirable. That means that bundler is probably the wrong tool to use to manage your gem directory. My personal recommendation would be to use RVM gemsets to sandbox your gems in certain projects or ruby versions.

How to solve "Unresolved inclusion: <iostream>" in a C++ file in Eclipse CDT?

Also set ${COMMAND} to g++ on Linux


  • Project
  • Properties
  • C/C++ General
  • Preprocessor Include Paths, Macros, etc.
  • Providers
  • CDT GCC Built-in Compiler Settings
  • Command to get compiler specs


${COMMAND} ${FLAGS} -E -P -v -dD "${INPUTS}"


g++ -std=c++11 -E -P -v -dD "${INPUTS}"

If you don't do this, the Eclipse stdout shows:

Unable to find full path for "-E"

and logs under ${HOME}/eclipse-workspace/.metadata/.log show:

!ENTRY org.eclipse.cdt.core 4 0 2020-04-23 20:17:07.288
!MESSAGE Error: Cannot run program "-E": Unknown reason

because ${COMMAND} ${FLAGS} are empty, and so Eclipse tries to execute the -E that comes next.

I wonder if we can properly define the COMMAND and FLAGS variables on the settings, but I tried to add them as build variables and it didn't work.

C version of the question: "Unresolved inclusion" error with Eclipse CDT for C standard library headers

Tested on Eclipse 2020-03 (4.15.0), Ubuntu 19.10, and this minimal Makefile project with existing sources.

Get file content from URL?

Use file_get_contents in combination with json_decode and echo.

Conversion of System.Array to List

Just use the existing method.. .ToList();

   List<int> listArray = array.ToList();


"Could not run curl-config: [Errno 2] No such file or directory" when installing pycurl

I encountered the same problem whilst trying to get Shinken 2.0.3 to fire up on Ubuntu. Eventually I did a full uninstall then reinstalled Shinken with pip -v. As it cleaned up, it mentioned:

Warning: missing python-pycurl lib, you MUST install it before launch the shinken daemons

Installed that with apt-get, and all the brokers fired up as expected :-)

Node.js: printing to console without a trailing newline?

util.print can be used also. Read:

util.print([...])# A synchronous output function. Will block the process, cast each argument to a string then output to stdout. Does not place newlines after each argument.

An example:

// get total length
var len = parseInt(response.headers['content-length'], 10);
var cur = 0;

// handle the response
response.on('data', function(chunk) {
  cur += chunk.length;
  util.print("Downloading " + (100.0 * cur / len).toFixed(2) + "% " + cur + " bytes\r");

Setting JDK in Eclipse

You manage the list of available compilers in the Window -> Preferences -> Java -> Installed JRE's tab.

In the project build path configuration dialog, under the libraries tab, you can delete the entry for JRE System Library, click on Add Library and choose the installed JRE to compile with. Some compilers can be configured to compile at a back-level compiler version. I think that's why you're seeing the addition version options.

Get average color of image via Javascript

Figured I'd post a project I recently came across to get dominant color:

Color Thief

A script for grabbing the dominant color or a representative color palette from an image. Uses javascript and canvas.

The other solutions mentioning and suggesting dominant color never really answer the question in proper context ("in javascript"). Hopefully this project will help those who want to do just that.

Detect if PHP session exists

The original code is from Sabry Suleiman.

Made it a bit prettier:

function is_session_started() {

    if ( php_sapi_name() === 'cli' )
        return false;

    return version_compare( phpversion(), '5.4.0', '>=' )
        ? session_status() === PHP_SESSION_ACTIVE
        : session_id() !== '';

First condition checks the Server API in use. If Command Line Interface is used, the function returns false.

Then we return the boolean result depending on the PHP version in use.

In ancient history you simply needed to check session_id(). If it's an empty string, then session is not started. Otherwise it is.

Since 5.4 to at least the current 8.0 the norm is to check session_status(). If it's not PHP_SESSION_ACTIVE, then either the session isn't started yet (PHP_SESSION_NONE) or sessions are not available altogether (PHP_SESSION_DISABLED).

How to turn off gcc compiler optimization to enable buffer overflow

Urm, all of the answers so far have been wrong with Rook's answer being correct.


echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

Followed by:

gcc -fno-stack-protector -z execstack -o bug bug.c

Disables ASLR, SSP/Propolice and Ubuntu's NoneXec (which was placed in 9.10, and fairly simple to work around see the mprotect(2) technique to map pages as executable and jmp) should help a little, however these "security features" are by no means infallible. Without the `-z execstack' flag, pages have non-executable stack markings.

Test method is inconclusive: Test wasn't run. Error?

I just fixed this issue as well. However, none of the solutions in this thread worked. Here's what I did...

Since R# wasn't giving any detail about why things were failing, I decided to try the built-in VS2013 test runner. It experienced the exact same behavior where none of the tests ran. However, looking in the Output window, I finally had an error message:

An exception occurred while invoking executor 'executor://mstestadapter/v1': Object reference not set to an instance of an object.

This led me to another thread on SO with a solution. Believe me, I would have NEVER guessed what the issue was.

I had recently made a few changes to the AssemblyInfo.cs file while creating a NuGet package. One of the changes including specifying an assembly culture value of "en".

I changed this:

[assembly: AssemblyCulture("")] 

to this:

[assembly: AssemblyCulture("en")]`. 

That was it! That's what inexplicably broke my unit tests. I still don't understand why, however. But at least things are working again. After I reverted this change (i.e. set the culture back to ""), my tests began running again.

Hope that helps somebody out there.

How to upload multiple files using PHP, jQuery and AJAX

My solution

  • Assuming that form id = "my_form_id"
  • It detects the form method and form action from HTML

jQuery code

$('#my_form_id').on('submit', function(e) {
    var formData = new FormData($(this)[0]);
    var msg_error = 'An error has occured. Please try again later.';
    var msg_timeout = 'The server is not responding';
    var message = '';
    var form = $('#my_form_id');
        data: formData,
        async: false,
        cache: false,
        processData: false,
        contentType: false,
        url: form.attr('action'),
        type: form.attr('method'),
        error: function(xhr, status, error) {
            if (status==="timeout") {
            } else {
        success: function(response) {
        timeout: 7000

What causes an HTTP 405 "invalid method (HTTP verb)" error when POSTing a form to PHP on IIS?

I managed to get FTP access to the customer's server and so was able to track down the problem.

After the form is POSTed, I authenticate the user and then redirect to the main part of the app.


The error was occurring not on the posting of the form, but on the redirect immediately following it. For some reason, IIS was continuing to presume the POST method for the redirect, and then objecting to the POST to /apps/content as it's a directory.

The error message never indicated that it was the following page that was generating the error - thanks Microsoft!

The solution was to add a trailing slash:


IIS could then resolve the redirect to a default document as is no longer attempting to POST to a directory.

bootstrap 3 navbar collapse button not working

In my case the issue was due to how I build my Nav bar. I was doing it through a jQuery plugin so I can quickly build Bootstrap components through javascript.

To cut a long story short binding the data elements of the button through jQuery .data() resulted in a collapse button that didn't work, doing it via .attr() fixed the issue.

This doesn't work:

$this.addClass("navbar navbar-default")
  .append($("<div />").addClass("container-fluid")
    .append($("<div />").addClass("navbar-header")
      .append($("<button />").addClass("navbar-toggle collapsed")
        .attr("aria-expanded", "false")
        .data("target","#" + id)
        .html("<span class='sr-only'>Toggle navigation</span>"
            + "<span class='icon-bar'></span>"
            + "<span class='icon-bar'></span>"
            + "<span class='icon-bar'></span>"))
        .append($("<a href='#' />").addClass("navbar-brand")
    .append($("<div />").addClass("collapse navbar-collapse").attr("id",id)));

But this does (with the changes left in comments):

$this.addClass("navbar navbar-default")
  .append($("<div />").addClass("container-fluid")
    .append($("<div />").addClass("navbar-header")
      .append($("<button />").addClass("navbar-toggle collapsed")
        .attr("aria-expanded", "false")
        .attr("data-target", "#" + id) //.data("target","#" + id)
        .attr("data-toggle", "collapse") // .data("toggle","collapse")
        .html("<span class='sr-only'>Toggle navigation</span>"
            + "<span class='icon-bar'></span>"
            + "<span class='icon-bar'></span>"
            + "<span class='icon-bar'></span>"))
        .append($("<a href='#' />").addClass("navbar-brand")
    .append($("<div />").addClass("collapse navbar-collapse").attr("id",id)));

I can only assume that this is related to the way jQuery binds .data(), it doesn't write the attributes out to the elements, but just attaches them to the jQuery object. Using the .data() version resulted in HTML:

<button class="navbar-toggle collapsed" aria-expanded="false" type="button" >

Where as the .attr() version gives:

<button class="navbar-toggle collapsed" aria-expanded="false" type="button" data-toggle="collapse" data-target="#6a2034fe-8922-4edd-920e-6bd0ea0b2caf">

It seems that Bootstrap needs the data-nnn attribute in the HTML.

Hash String via SHA-256 in Java

To hash a string, use the built-in MessageDigest class:

import java.nio.charset.StandardCharsets;
import java.math.BigInteger;

public class CryptoHash {
  public static void main(String[] args) throws NoSuchAlgorithmException {
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    String text = "Text to hash, cryptographically.";

    // Change this to UTF-16 if needed
    byte[] digest = md.digest();

    String hex = String.format("%064x", new BigInteger(1, digest));

In the snippet above, digest contains the hashed string and hex contains a hexadecimal ASCII string with left zero padding.

How can I use Guzzle to send a POST request in JSON?

I use the following code that works very reliably.

The JSON data is passed in the parameter $request, and the specific request type passed in the variable $searchType.

The code includes a trap to detect and report an unsuccessful or invalid call which will then return false.

If the call is sucessful then json_decode ($result->getBody(), $return=true) returns an array of the results.

    public function callAPI($request, $searchType) {
    $guzzleClient = new GuzzleHttp\Client(["base_uri" => ""]);

    try {
        $result = $guzzleClient->post( $searchType, ["json" => $request]);
    } catch (Exception $e) {
        $error = $e->getMessage();
        $error .= '<pre>'.print_r($request, $return=true).'</pre>';
        $error .= 'No returnable data';
        Event::logError(__LINE__, __FILE__, $error);
        return false;
    return json_decode($result->getBody(), $return=true);