Programs & Examples On #Artificial intelligence

Artificial intelligence (AI) is the branch of computer science and technology that studies the development of machines able to simulate aspects of human intelligence. This tag may also refer to the part of a computer game application that controls the behavior of the virtual characters with which the player may interact during the game.

Best programming based games

In the flash game Manufactoria you "program" a factory by laying out the conveyor belts and switches in a way that's very similar to a FSM, but more powerful. This game is really great. Give it a try, especially if you're into formal languages and automata!

Manufactoria screen shot

How to compute precision, recall, accuracy and f1-score for the multiclass case with scikit learn?

I think there is a lot of confusion about which weights are used for what. I am not sure I know precisely what bothers you so I am going to cover different topics, bear with me ;).

Class weights

The weights from the class_weight parameter are used to train the classifier. They are not used in the calculation of any of the metrics you are using: with different class weights, the numbers will be different simply because the classifier is different.

Basically in every scikit-learn classifier, the class weights are used to tell your model how important a class is. That means that during the training, the classifier will make extra efforts to classify properly the classes with high weights.
How they do that is algorithm-specific. If you want details about how it works for SVC and the doc does not make sense to you, feel free to mention it.

The metrics

Once you have a classifier, you want to know how well it is performing. Here you can use the metrics you mentioned: accuracy, recall_score, f1_score...

Usually when the class distribution is unbalanced, accuracy is considered a poor choice as it gives high scores to models which just predict the most frequent class.

I will not detail all these metrics but note that, with the exception of accuracy, they are naturally applied at the class level: as you can see in this print of a classification report they are defined for each class. They rely on concepts such as true positives or false negative that require defining which class is the positive one.

             precision    recall  f1-score   support

          0       0.65      1.00      0.79        17
          1       0.57      0.75      0.65        16
          2       0.33      0.06      0.10        17
avg / total       0.52      0.60      0.51        50

The warning

F1 score:/usr/local/lib/python2.7/site-packages/sklearn/metrics/ DeprecationWarning: The 
default `weighted` averaging is deprecated, and from version 0.18, 
use of precision, recall or F-score with multiclass or multilabel data  
or pos_label=None will result in an exception. Please set an explicit 
value for `average`, one of (None, 'micro', 'macro', 'weighted', 
'samples'). In cross validation use, for instance, 
scoring="f1_weighted" instead of scoring="f1".

You get this warning because you are using the f1-score, recall and precision without defining how they should be computed! The question could be rephrased: from the above classification report, how do you output one global number for the f1-score? You could:

  1. Take the average of the f1-score for each class: that's the avg / total result above. It's also called macro averaging.
  2. Compute the f1-score using the global count of true positives / false negatives, etc. (you sum the number of true positives / false negatives for each class). Aka micro averaging.
  3. Compute a weighted average of the f1-score. Using 'weighted' in scikit-learn will weigh the f1-score by the support of the class: the more elements a class has, the more important the f1-score for this class in the computation.

These are 3 of the options in scikit-learn, the warning is there to say you have to pick one. So you have to specify an average argument for the score method.

Which one you choose is up to how you want to measure the performance of the classifier: for instance macro-averaging does not take class imbalance into account and the f1-score of class 1 will be just as important as the f1-score of class 5. If you use weighted averaging however you'll get more importance for the class 5.

The whole argument specification in these metrics is not super-clear in scikit-learn right now, it will get better in version 0.18 according to the docs. They are removing some non-obvious standard behavior and they are issuing warnings so that developers notice it.

Computing scores

Last thing I want to mention (feel free to skip it if you're aware of it) is that scores are only meaningful if they are computed on data that the classifier has never seen. This is extremely important as any score you get on data that was used in fitting the classifier is completely irrelevant.

Here's a way to do it using StratifiedShuffleSplit, which gives you a random splits of your data (after shuffling) that preserve the label distribution.

from sklearn.datasets import make_classification
from sklearn.cross_validation import StratifiedShuffleSplit
from sklearn.metrics import accuracy_score, f1_score, precision_score, recall_score, classification_report, confusion_matrix

# We use a utility to generate artificial classification data.
X, y = make_classification(n_samples=100, n_informative=10, n_classes=3)
sss = StratifiedShuffleSplit(y, n_iter=1, test_size=0.5, random_state=0)
for train_idx, test_idx in sss:
    X_train, X_test, y_train, y_test = X[train_idx], X[test_idx], y[train_idx], y[test_idx], y_train)
    y_pred = svc.predict(X_test)
    print(f1_score(y_test, y_pred, average="macro"))
    print(precision_score(y_test, y_pred, average="macro"))
    print(recall_score(y_test, y_pred, average="macro"))    

Hope this helps.

What is the difference between supervised learning and unsupervised learning?

Supervised learning

Applications in which the training data comprises examples of the input vectors along with their corresponding target vectors are known as supervised learning problems.

Unsupervised learning

In other pattern recognition problems, the training data consists of a set of input vectors x without any corresponding target values. The goal in such unsupervised learning problems may be to discover groups of similar examples within the data, where it is called clustering

Pattern Recognition and Machine Learning (Bishop, 2006)

What's is the difference between train, validation and test set, in neural networks?

Training Dataset: The sample of data used to fit the model.

Validation Dataset: The sample of data used to provide an unbiased evaluation of a model fit on the training dataset while tuning model hyperparameters. The evaluation becomes more biased as skill on the validation dataset is incorporated into the model configuration.

Test Dataset: The sample of data used to provide an unbiased evaluation of a final model fit on the training dataset.

Epoch vs Iteration when training neural networks

To understand the difference between these you must understand the Gradient Descent Algorithm and its Variants.

Before I start with the actual answer, I would like to build some background.

A batch is the complete dataset. Its size is the total number of training examples in the available dataset.

Mini-batch size is the number of examples the learning algorithm processes in a single pass (forward and backward).

A Mini-batch is a small part of the dataset of given mini-batch size.

Iterations is the number of batches of data the algorithm has seen (or simply the number of passes the algorithm has done on the dataset).

Epochs is the number of times a learning algorithm sees the complete dataset. Now, this may not be equal to the number of iterations, as the dataset can also be processed in mini-batches, in essence, a single pass may process only a part of the dataset. In such cases, the number of iterations is not equal to the number of epochs.

In the case of Batch gradient descent, the whole batch is processed on each training pass. Therefore, the gradient descent optimizer results in smoother convergence than Mini-batch gradient descent, but it takes more time. The batch gradient descent is guaranteed to find an optimum if it exists.

Stochastic gradient descent is a special case of mini-batch gradient descent in which the mini-batch size is 1.

Batch gradient descent vs Mini-batch gradient descent

Comparison of batch, stochastic and mini-batch gradient descents.

source of historical stock data

Why not model a fake stock market with Brownian Motion?

Plenty of resources for doing it. Easy to implement.

What is the role of the bias in neural networks?

A layer in a neural network without a bias is nothing more than the multiplication of an input vector with a matrix. (The output vector might be passed through a sigmoid function for normalisation and for use in multi-layered ANN afterwards but that’s not important.)

This means that you’re using a linear function and thus an input of all zeros will always be mapped to an output of all zeros. This might be a reasonable solution for some systems but in general it is too restrictive.

Using a bias, you’re effectively adding another dimension to your input space, which always takes the value one, so you’re avoiding an input vector of all zeros. You don’t lose any generality by this because your trained weight matrix needs not be surjective, so it still can map to all values previously possible.

2d ANN:

For a ANN mapping two dimensions to one dimension, as in reproducing the AND or the OR (or XOR) functions, you can think of a neuronal network as doing the following:

On the 2d plane mark all positions of input vectors. So, for boolean values, you’d want to mark (-1,-1), (1,1), (-1,1), (1,-1). What your ANN now does is drawing a straight line on the 2d plane, separating the positive output from the negative output values.

Without bias, this straight line has to go through zero, whereas with bias, you’re free to put it anywhere. So, you’ll see that without bias you’re facing a problem with the AND function, since you can’t put both (1,-1) and (-1,1) to the negative side. (They are not allowed to be on the line.) The problem is equal for the OR function. With a bias, however, it’s easy to draw the line.

Note that the XOR function in that situation can’t be solved even with bias.

What algorithm for a tic-tac-toe game can I use to determine the "best move" for the AI?

A typical algo for tic-tac-toe should look like this:

Board : A nine-element vector representing the board. We store 2 (indicating Blank), 3 (indicating X), or 5 (indicating O). Turn: An integer indicating which move of the game about to be played. The 1st move will be indicated by 1, last by 9.

The Algorithm

The main algorithm uses three functions.

Make2: returns 5 if the center square of the board is blank i.e. if board[5]=2. Otherwise, this function returns any non-corner square (2, 4, 6 or 8).

Posswin(p): Returns 0 if player p can’t win on his next move; otherwise, it returns the number of the square that constitutes a winning move. This function will enable the program both to win and to block opponents win. This function operates by checking each of the rows, columns, and diagonals. By multiplying the values of each square together for an entire row (or column or diagonal), the possibility of a win can be checked. If the product is 18 (3 x 3 x 2), then X can win. If the product is 50 (5 x 5 x 2), then O can win. If a winning row (column or diagonal) is found, the blank square in it can be determined and the number of that square is returned by this function.

Go (n): makes a move in square n. this procedure sets board [n] to 3 if Turn is odd, or 5 if Turn is even. It also increments turn by one.

The algorithm has a built-in strategy for each move. It makes the odd numbered move if it plays X, the even-numbered move if it plays O.

Turn = 1    Go(1)   (upper left corner).
Turn = 2    If Board[5] is blank, Go(5), else Go(1).
Turn = 3    If Board[9] is blank, Go(9), else Go(3).
Turn = 4    If Posswin(X) is not 0, then Go(Posswin(X)) i.e. [ block opponent’s win], else Go(Make2).
Turn = 5    if Posswin(X) is not 0 then Go(Posswin(X)) [i.e. win], else if Posswin(O) is not 0, then Go(Posswin(O)) [i.e. block win], else if Board[7] is blank, then Go(7), else Go(3). [to explore other possibility if there be any ].
Turn = 6    If Posswin(O) is not 0 then Go(Posswin(O)), else if Posswin(X) is not 0, then Go(Posswin(X)), else Go(Make2).
Turn = 7    If Posswin(X) is not 0 then Go(Posswin(X)), else if Posswin(X) is not 0, then Go(Posswin(O)) else go anywhere that is blank.
Turn = 8    if Posswin(O) is not 0 then Go(Posswin(O)), else if Posswin(X) is not 0, then Go(Posswin(X)), else go anywhere that is blank.
Turn = 9    Same as Turn=7.

I have used it. Let me know how you guys feel.

How to get Tensorflow tensor dimensions (shape) as int values?

Another simple solution is to use map() as follows:

tensor_shape = map(int, my_tensor.shape)

This converts all the Dimension objects to int

What is the optimal algorithm for the game 2048?


    for each possible move:
        evaluate next state

    choose the maximum evaluation


Evaluation =
    128 (Constant)
    + (Number of Spaces x 128)
    + Sum of faces adjacent to a space { (1/face) x 4096 }
    + Sum of other faces { log(face) x 4 }
    + (Number of possible next moves x 256)
    + (Number of aligned values x 2)

Evaluation Details

128 (Constant)

This is a constant, used as a base-line and for other uses like testing.

+ (Number of Spaces x 128)

More spaces makes the state more flexible, we multiply by 128 (which is the median) since a grid filled with 128 faces is an optimal impossible state.

+ Sum of faces adjacent to a space { (1/face) x 4096 }

Here we evaluate faces that have the possibility to getting to merge, by evaluating them backwardly, tile 2 become of value 2048, while tile 2048 is evaluated 2.

+ Sum of other faces { log(face) x 4 }

In here we still need to check for stacked values, but in a lesser way that doesn't interrupt the flexibility parameters, so we have the sum of { x in [4,44] }.

+ (Number of possible next moves x 256)

A state is more flexible if it has more freedom of possible transitions.

+ (Number of aligned values x 2)

This is a simplified check of the possibility of having merges within that state, without making a look-ahead.

Note: The constants can be tweaked..

What are good examples of genetic algorithms/genetic programming solutions?

I developed a home brew GA for a 3D laser surface profile system my company developed for the freight industry back in 1992. The system relied upon 3 dimensional triangulation and used a custom laser line scanner, a 512x512 camera (with custom capture hw). The distance between the camera and laser was never going to be precise and the focal point of the cameras were not to be found in the 256,256 position that you expected it to be!

It was a nightmare to try and work out the calibration parameters using standard geometry and simulated annealing style equation solving.

The Genetic algorithm was whipped up in an evening and I created a calibration cube to test it on. I knew the cube dimensions to high accuracy and thus the idea was that my GA could evolve a set of custom triangulation parameters for each scanning unit that would overcome production variations.

The trick worked a treat. I was flabbergasted to say the least! Within around 10 generations my 'virtual' cube (generated from the raw scan and recreated from the calibration parameters) actually looked like a cube! After around 50 generations I had the calibration I needed.

How to tell if browser/tab is active

You would use the focus and blur events of the window:

var interval_id;
$(window).focus(function() {
    if (!interval_id)
        interval_id = setInterval(hard_work, 1000);

$(window).blur(function() {
    interval_id = 0;

To Answer the Commented Issue of "Double Fire" and stay within jQuery ease of use:

$(window).on("blur focus", function(e) {
    var prevType = $(this).data("prevType");

    if (prevType != e.type) {   //  reduce double fire issues
        switch (e.type) {
            case "blur":
                // do work
            case "focus":
                // do work

    $(this).data("prevType", e.type);

Click to view Example Code Showing it working (JSFiddle)

Error 1046 No database Selected, how to resolve?

Although this is a pretty old thread, I just found something out. I created a new database, then added a user, and finally went to use phpMyAdmin to upload the .sql file. total failure. The system doesn't recognize which DB I'm aiming at...

When I start fresh WITHOUT first attaching a new user, and then perform the same phpMyAdmin import, it works fine.

TypeScript and React - children type?

In order to use <Aux> in your JSX, it needs to be a function that returns ReactElement<any> | null. That's the definition of a function component.

However, it's currently defined as a function that returns React.ReactNode, which is a much wider type. As React typings say:

type ReactNode = ReactChild | ReactFragment | ReactPortal | boolean | null | undefined;

Make sure the unwanted types are neutralized by wrapping the returned value into React Fragment (<></>):

const aux: React.FC<AuxProps> = props =>

Rename multiple files based on pattern in Unix

rename might not be in every system. so if you don't have it, use the shell this example in bash shell

for f in fgh*; do mv "$f" "${f/fgh/xxx}";done

How do I vertically align text in a paragraph?

Below styles will vertically center it for you.

p.event_desc {
 font: bold 12px "Helvetica Neue", Helvetica, Arial, sans-serif;
 line-height: 14px;
 height: 35px;
 display: table-cell;
 vertical-align: middle;
 margin: 0px;

Getting the parameters of a running JVM

_JAVA_OPTIONS is an env variable that can be expanded.


Spring 5.0.3 RequestRejectedException: The request was rejected because the URL was not normalized

setAllowUrlEncodedSlash(true) didn't work for me. Still internal method isNormalized return false when having double slash.

I replaced StrictHttpFirewall with DefaultHttpFirewall by having the following code only:

public HttpFirewall defaultHttpFirewall() {
    return new DefaultHttpFirewall();

Working well for me.
Any risk by using DefaultHttpFirewall?

Python truncate a long string

       >>> info = lambda data: len(data)>10 and data[:10]+'...' or data
       >>> info('sdfsdfsdfsdfsdfsdfsdfsdfsdfsdfsdf')
       >>> info('sdfsdf')

Entity Framework - Code First - Can't Store List<String>

You can use this ScalarCollection container that confines an array and provides some manipulation options (Gist):


public class Person
    public int Id { get; set; }
    //will be stored in database as single string.
    public SaclarStringCollection Phones { get; set; } = new ScalarStringCollection();


using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;

namespace System.Collections.Specialized
#if NET462
  public abstract class ScalarCollectionBase<T> :
#if NET462
    public virtual string Separator { get; } = "\n";
    public virtual string ReplacementChar { get; } = " ";
    public ScalarCollectionBase(params T[] values)
      if (values != null)
        foreach (var item in Items)

#if NET462
    [Obsolete("Not to be used directly by user, use Items property instead.")]
    public string Data
        var data = Items.Select(item => Serialize(item)
          .Replace(Separator, ReplacementChar.ToString()));
        return string.Join(Separator, data.Where(s => s?.Length > 0));
        if (string.IsNullOrWhiteSpace(value))

        foreach (var item in value
            .Split(new[] { Separator }, 
              StringSplitOptions.RemoveEmptyEntries).Select(item => Deserialize(item)))

    public void AddRange(params T[] items)
      if (items != null)
        foreach (var item in items)

    protected abstract string Serialize(T item);
    protected abstract T Deserialize(string item);

  public class ScalarStringCollection : ScalarCollectionBase<string>
    protected override string Deserialize(string item) => item;
    protected override string Serialize(string item) => item;

  public class ScalarCollection<T> : ScalarCollectionBase<T>
    where T : IConvertible
    protected override T Deserialize(string item) =>
      (T)Convert.ChangeType(item, typeof(T));
    protected override string Serialize(T item) => Convert.ToString(item);

Composer: file_put_contents(./composer.json): failed to open stream: Permission denied

I was getting the same exception, but in my case I am using PowerShell to run commands So, I fixed this with an instruction to unblock multiple files first. PS C:\> dir C:\executable_file_Path\*PowerShell* | Unblock-File and then use the following to load the package & 'C:\path_to_executable\php.exe' "c:\path_to_composer_.phar_file\composer.phar "require desired/package

Download all stock symbol list of a market

This may be old, but... if you change the link in google stock list as below:

  • note for the noIL=1&num=30000

It means, starting for row 1 to 30000. It shows all results in one page.

You may automate it using any language or just export the table to excel.

Hope it helps.

ASP MVC in IIS 7 results in: HTTP Error 403.14 - Forbidden

I know this is an old topic, but you can also get this error (when you are debugging) if you have a folder named the same as a route in a controller.

For instance, if you have a UserController, with a route called /User and you ALSO have a folder in your solution called "User" then IISExpress will try to browse the folder instead of showing your view.

Python reading from a file and saving to utf-8

Process text to and from Unicode at the I/O boundaries of your program using open with the encoding parameter. Make sure to use the (hopefully documented) encoding of the file being read. The default encoding varies by OS (specifically, locale.getpreferredencoding(False) is the encoding used), so I recommend always explicitly using the encoding parameter for portability and clarity (Python 3 syntax below):

with open(filename, 'r', encoding='utf8') as f:
    text =

# process Unicode text

with open(filename, 'w', encoding='utf8') as f:

If still using Python 2 or for Python 2/3 compatibility, the io module implements open with the same semantics as Python 3's open and exists in both versions:

import io
with, 'r', encoding='utf8') as f:
    text =

# process Unicode text

with, 'w', encoding='utf8') as f:

How to configure Glassfish Server in Eclipse manually

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

Using Razor within JavaScript

What specific errors are you seeing?

Something like this could work better:

<script type="text/javascript">

//now add markers
 @foreach (var item in Model) {
      var markerlatLng = new google.maps.LatLng(@Model.Latitude, @Model.Longitude);
      var title = '@(Model.Title)';
      var description = '@(Model.Description)';
      var contentString = '<h3>' + title + '</h3>' + '<p>' + description + '</p>'

Note that you need the magical <text> tag after the foreach to indicate that Razor should switch into markup mode.

Lotus Notes email as an attachment to another email

  1. Open msg
  2. Save to desktop
  3. Open new mail
  4. Attached *.eml file on desktop

Sad to say, this is the only way I know which sux because in Outlook, you just need to copy and paste.

Package opencv was not found in the pkg-config search path

Hi first of all i would like you to use 'Synaptic Package Manager'. You just need to goto the ubuntu software center and search for synaptic package manager.. The beauty of this is that all the packages you need are easily available here. Second it will automatically configures all your paths. Now install this then search for opencv packages over there if you found the package with the green box then its installed but else the package is not in the right place so you need to reinstall it but from package manager this time. If installed then you can do this only, you just need to fill the OpenCV_DIR variable with the path of opencv (containing the OpenCVConfig.cmake file)

    export OpenCV_DIR=<path_of_opencv>

post ajax data to PHP and return data

So what does count_votes look like? Is it a script? Anything that you want to get back from an ajax call can be retrieved using a simple echo (of course you could use JSON or xml, but for this simple example you would just need to output something in count_votes.php like:

$id = $_POST['id'];

function getVotes($id){
    // call your database here
    $query = ("SELECT votes FROM poll WHERE ID = $id");
    $result = @mysql_query($query);
    $row = mysql_fetch_row($result);

    return $row->votes;
$votes = getVotes($id);
echo $votes;

This is just pseudocode, but should give you the idea. What ever you echo from count_votes will be what is returned to "data" in your ajax call.

Using AND/OR in if else PHP statement

You have 2 issues here.

  1. use == for comparison. You've used = which is for assignment.

  2. use && for "and" and || for "or". and and or will work but they are unconventional.

Undefined Symbols for architecture x86_64: Compiling problems

There's no mystery here, the linker is telling you that you haven't defined the missing symbols, and you haven't.

Similarity::Similarity() or Similarity::~Similarity() are just missing and you have defined the others incorrectly,

void Similarity::readData(Scanner& inStream){


void readData(Scanner& inStream){

etc. etc.

The second one is a function called readData, only the first is the readData method of the Similarity class.

To be clear about this, in Similarity.h

void readData(Scanner& inStream);

but in Similarity.cpp

void Similarity::readData(Scanner& inStream){

ERROR Error: No value accessor for form control with unspecified name attribute on switch

In my case it was as daft as having registered the new component for DI in my app.module.ts declarations but not in exports.

Replace HTML Table with Divs

I looked all over for an easy solution and found this code that worked for me. The right div is a third column which I left in for readability sake.

Here is the HTML:

<div class="container">
  <div class="row">
    <div class="left">
      <p>PHONE & FAX:</p>
    <div class="middle">
      <p>+43 99 554 28 53</p>
    <div class="right"> </div>
  <div class="row">
    <div class="left">
      <p>Cellphone Gert:</p>
    <div class="middle">
      <p>+43 99 302 52 32</p>
    <div class="right"> </div>
  <div class="row">
    <div class="left">
      <p>Cellphone Petra:</p>
    <div class="middle">
      <p>+43 99 739 38 84</p>
    <div class="right"> </div>

And the CSS:

.container {
    display: table;
.row  {
    display: table-row;
.left, .right, .middle {
    display: table-cell;
    padding-right: 25px;
.left p, .right p, .middle p {
    margin: 1px 1px;

"NOT IN" clause in LINQ to Entities

I took a list and used,


Note: Make sure to use List and not Ilist

Cancel a UIView animation?

If you are animating a constraint by changing the constant instead of a view property none of the other methods work on iOS 8.

Example animation:

self.constraint.constant = 0;
[self.view updateConstraintsIfNeeded];
[self.view layoutIfNeeded];
[UIView animateWithDuration:1.0f
                     self.constraint.constant = 1.0f;
                     [self.view layoutIfNeeded];
                 } completion:^(BOOL finished) {



You need to remove the animations from the layers of any views being affected by the constraint change and their sublayers.

[self.constraintView.layer removeAllAnimations];
for (CALayer *l in self.constraintView.layer.sublayers)
    [l removeAllAnimations];

iPhone keyboard, Done button and resignFirstResponder

From the documentation (any version):

It is your application’s responsibility to dismiss the keyboard at the time of your choosing. You might dismiss the keyboard in response to a specific user action, such as the user tapping a particular button in your user interface. You might also configure your text field delegate to dismiss the keyboard when the user presses the “return” key on the keyboard itself. To dismiss the keyboard, send the resignFirstResponder message to the text field that is currently the first responder. Doing so causes the text field object to end the current editing session (with the delegate object’s consent) and hide the keyboard.

So, you have to send resignFirstResponder somehow. But there is a possibility that textfield loses focus another way during processing of textFieldShouldReturn: message. This also will cause keyboard to disappear.

How to limit the maximum files chosen when using multiple file input

Use two <input type=file> elements instead, without the multiple attribute.

Transition color fade on hover?

What do you want to fade? The background or color attribute?

Currently you're changing the background color, but telling it to transition the color property. You can use all to transition all properties.

.clicker { 
    -moz-transition: all .2s ease-in;
    -o-transition: all .2s ease-in;
    -webkit-transition: all .2s ease-in;
    transition: all .2s ease-in;
    background: #f5f5f5; 
    padding: 20px;

.clicker:hover { 
    background: #eee;

Otherwise just use transition: background .2s ease-in.

Node.js: Difference between req.query[] and req.params

Given this route

app.get('/hi/:param1', function(req,res){} );

and given this URL

You will have:


  qs1: 'you',
  qs2: 'tube'


  param1: 'there'

Express req.params >>

Casting variables in Java

Casting a reference will only work if it's an instanceof that type. You can't cast random references. Also, you need to read more on Casting Objects.


String string = "String";

Object object = string; // Perfectly fine since String is an Object

String newString = (String)object; // This only works because the `reference` object is pointing to a valid String object.

Different ways of adding to Dictionary

The first version will add a new KeyValuePair to the dictionary, throwing if key is already in the dictionary. The second, using the indexer, will add a new pair if the key doesn't exist, but overwrite the value of the key if it already exists in the dictionary.

IDictionary<string, string> strings = new Dictionary<string, string>();

strings["foo"] = "bar";          //strings["foo"] == "bar"
strings["foo"] = string.Empty;   //strings["foo"] == string.empty
strings.Add("foo", "bar");       //throws     

How do I check if a list is empty?

Patrick's (accepted) answer is right: if not a: is the right way to do it. Harley Holcombe's answer is right that this is in the PEP 8 style guide. But what none of the answers explain is why it's a good idea to follow the idiom—even if you personally find it's not explicit enough or confusing to Ruby users or whatever.

Python code, and the Python community, has very strong idioms. Following those idioms makes your code easier to read for anyone experienced in Python. And when you violate those idioms, that's a strong signal.

It's true that if not a: doesn't distinguish empty lists from None, or numeric 0, or empty tuples, or empty user-created collection types, or empty user-created not-quite-collection types, or single-element NumPy array acting as scalars with falsey values, etc. And sometimes it's important to be explicit about that. And in that case, you know what you want to be explicit about, so you can test for exactly that. For example, if not a and a is not None: means "anything falsey except None", while if len(a) != 0: means "only empty sequences—and anything besides a sequence is an error here", and so on. Besides testing for exactly what you want to test, this also signals to the reader that this test is important.

But when you don't have anything to be explicit about, anything other than if not a: is misleading the reader. You're signaling something as important when it isn't. (You may also be making the code less flexible, or slower, or whatever, but that's all less important.) And if you habitually mislead the reader like this, then when you do need to make a distinction, it's going to pass unnoticed because you've been "crying wolf" all over your code.

Get DOM content of cross-domain iframe

There is a simple way.

  1. You create an iframe which have for source something like "

  2. Then, you just get this url with $_GET and display the contents with file_get_contents($_GET['url']);

You will obtain an iframe which has a domain same than yours, then you will be able to use the $("iframe").contents().find("body") to manipulate the content.

JavaScript math, round to two decimal places

try using discount.toFixed(2);

How to stop line breaking in vim

You may find set lbr useful; with set wrap on this will wrap but only cutting the line on whitespace and not in the middle of a word.


without lbr the li
ne can be split on
a word


with lbr on the
line will be
split on 
whitespace only

Converting XDocument to XmlDocument and vice versa

If you need a Win 10 UWP compatible variant:

using DomXmlDocument = Windows.Data.Xml.Dom.XmlDocument;

    public static class DocumentExtensions
        public static XmlDocument ToXmlDocument(this XDocument xDocument)
            var xmlDocument = new XmlDocument();
            using (var xmlReader = xDocument.CreateReader())
            return xmlDocument;

        public static DomXmlDocument ToDomXmlDocument(this XDocument xDocument)
            var xmlDocument = new DomXmlDocument();
            using (var xmlReader = xDocument.CreateReader())
            return xmlDocument;

        public static XDocument ToXDocument(this XmlDocument xmlDocument)
            using (var memStream = new MemoryStream())
                using (var w = XmlWriter.Create(memStream))
                memStream.Seek(0, SeekOrigin.Begin);
                using (var r = XmlReader.Create(memStream))
                    return XDocument.Load(r);

        public static XDocument ToXDocument(this DomXmlDocument xmlDocument)
            using (var memStream = new MemoryStream())
                using (var w = XmlWriter.Create(memStream))
                memStream.Seek(0, SeekOrigin.Begin);
                using (var r = XmlReader.Create(memStream))
                    return XDocument.Load(r);

json_encode() escaping forward slashes

Yes, but don't - escaping forward slashes is a good thing. When using JSON inside <script> tags it's necessary as a </script> anywhere - even inside a string - will end the script tag.

Depending on where the JSON is used it's not necessary, but it can be safely ignored.

Apache is not running from XAMPP Control Panel ( Error: Apache shutdown unexpectedly. This may be due to a blocked port)

i have found that similar issue on my system, and that was from skype installed before xampp installed. i got similar error. for fixing the error i followed these,

  1. logged out to skype for a while ,
  2. restarted apache from xampp control panel,
  3. checked on browser, whether it worked or not, by http://localhost/
  4. got it worked,
  5. signed in again to skype,
  6. all working great, as simple as that

i wasn't need nothing to install or uninstall, and this worked for me in less then 1 minute.


How to code a modulo (%) operator in C/C++/Obj-C that handles negative numbers

The simplest general function to find the positive modulo would be this- It would work on both positive and negative values of x.

int modulo(int x,int N){
    return (x % N + N) %N;

What is the meaning of CTOR?

To expand a little more, there are two kinds of constructors: instance initializers (.ctor), type initializers (.cctor). Build the code below, and explore the IL code in ildasm.exe. You will notice that the static field 'b' will be initialized through .cctor() whereas the instance field will be initialized through .ctor()

internal sealed class CtorExplorer
   protected int a = 0;
   protected static int b = 0;

android.os.NetworkOnMainThreadException with android 4.2

Use StrictMode Something like this:-

   if (android.os.Build.VERSION.SDK_INT > 9) {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();


Getting a list of files in a directory with a glob

I won't pretend to be an expert on the topic, but you should have access to both the glob and wordexp function from objective-c, no?

Formatting a double to two decimal places

    double d =  3.1493745;
    string s = $"{d:0.00}"; // or $"{d:#.##}"
    Console.WriteLine(s); // Displays 3.15

How to select a node of treeview programmatically in c#?

yourNode.Toggle(); //use that function on your node, it toggles it

"CSV file does not exist" for a filename with embedded quotes

I also experienced the same problem I solved as follows:

dataset = pd.read_csv('C:\\Users\\path\\to\\file.csv')

Bulk package updates using Conda

the Conda Package Manager is almost ready for beta testing, but it will not be fully integrated until the release of Spyder 2.4 ( As soon as we have it ready for testing we will post something on the mailing list (!forum/spyderlib). Be sure to subscribe


How to change the default background color white to something else in twitter bootstrap

I would not recommend changing the actual bootstrap CSS files. If you do not want to use Jako's first solution you can create a custom bootstrap style sheet with one of the available Bootstrap theme generator (Bootstrap theme generators). That way you can use 1 style sheet with all of the default Bootstrap CSS with just the one change to it that you want. With a Bootstrap theme generator you do not need to write any CSS. You only need to set the hex values for the color you want for the body (Scaffolding; bodyBackground).

"android.view.WindowManager$BadTokenException: Unable to add window" on

I try this it solved.

 AlertDialog.Builder builder = new AlertDialog.Builder(

            builder.setMessage("You Don't have anough coins to withdraw. ");
            builder.setMessage("Please read the Withdraw rules.");
                    (dialog, which) -> dialog.dismiss());

Difference between PCDATA and CDATA in DTD

PCDATA – parsed character data. It parses all the data in an XML document.



Here, the <family> element contains 2 more elements: <mother> and <father>. So it parses further to get the text of mother and father to give the text value of family as “mom dad”

CDATA – unparsed character Data. This is the data that should not be parsed further in an xml document.


Here, the text value of family will be <mother>mom</mother><father>dad</father>.

How to get the list of all installed color schemes in Vim?

Here is a small function I wrote to try all the colorschemes in $VIMRUNTIME/colors directory.

Add the below function to your vimrc, then open your source file and call the function from command.

function! DisplayColorSchemes()
   let currDir = getcwd()
   exec "cd $VIMRUNTIME/colors"
   for myCol in split(glob("*"), '\n')
      if myCol =~ '\.vim'
         let mycol = substitute(myCol, '\.vim', '', '')
         exec "colorscheme " . mycol
         exec "redraw!"
         echo "colorscheme = ". myCol
         sleep 2
   exec "cd " . currDir

How can I call a WordPress shortcode within a template?

echo do_shortcode('[CONTACT-US-FORM]');

Use this in your template.

Look here for more: Do Shortcode

Change background of LinearLayout in Android

u just used attribute

  • android:background="#ColorCode" for colors

    if your image save in drawable folder then used :-

  • android:background="@drawable/ImageName" for image setting

Rounded Corners Image in Flutter

Use this Way in this circle image is also working + you have preloader also for network image:

new ClipRRect(
     borderRadius: new BorderRadius.circular(30.0),
     child: FadeInImage.assetNetwork(
          image: 'Your Image Path',

How to convert a string Date to long millseconds

Take a look to SimpleDateFormat class that can parse a String and return a Date and the getTime method of Date class.

PL/pgSQL checking if a row exists

Use count(*)

   cnt integer;
  SELECT count(*) INTO cnt
  FROM people
  WHERE person_id = my_person_id;

IF cnt > 0 THEN
  -- Do something

Edit (for the downvoter who didn't read the statement and others who might be doing something similar)

The solution is only effective because there is a where clause on a column (and the name of the column suggests that its the primary key - so the where clause is highly effective)

Because of that where clause there is no need to use a LIMIT or something else to test the presence of a row that is identified by its primary key. It is an effective way to test this.

How can I restart a Java application?

Basically, you can't. At least not in a reliable way. However, you shouldn't need to.

The can't part

To restart a Java program, you need to restart the JVM. To restart the JVM you need to

  1. Locate the java launcher that was used. You may try with System.getProperty("java.home") but there's no guarantee that this will actually point to the launcher that was used to launch your application. (The value returned may not point to the JRE used to launch the application or it could have been overridden by -Djava.home.)

  2. You would presumably want to honor the original memory settings etc (-Xmx, -Xms, …) so you need to figure out which settings where used to start the first JVM. You could try using ManagementFactory.getRuntimeMXBean().getInputArguments() but there's no guarantee that this will reflect the settings used. This is even spelled out in the documentation of that method:

    Typically, not all command-line options to the 'java' command are passed to the Java virtual machine. Thus, the returned input arguments may not include all command-line options.

  3. If your program reads input from the original stdin will be lost in the restart.

  4. Lots of these tricks and hacks will fail in the presence of a SecurityManager.

The shouldn't need part

I recommend you to design your application so that it is easy to clean every thing up and after that create a new instance of your "main" class.

Many applications are designed to do nothing but create an instance in the main-method:

public class MainClass {
    public static void main(String[] args) {
        new MainClass().launch();

By using this pattern, it should be easy enough to do something like:

public class MainClass {
    public static void main(String[] args) {
        boolean restart;
        do {
            restart = new MainClass().launch();
        } while (restart);

and let launch() return true if and only if the application was shut down in a way that it needs to be restarted.

How to add items to a spinner in Android?

Try this code:

final List<String> list = new ArrayList<String>();
list.add("Item 1");
list.add("Item 2");
list.add("Item 3");
list.add("Item 4");
list.add("Item 5");

final String[] str = {"Report 1", "Report 2", "Report 3", "Report 4", "Report 5"};

final Spinner sp1 = (Spinner) findViewById(;
final Spinner sp2 = (Spinner) findViewById(;

ArrayAdapter<String> adp1 = new ArrayAdapter<String>(this,
                              android.R.layout.simple_list_item_1, list);

ArrayAdapter<String> adp2 = new ArrayAdapter<String>(this,
                                  android.R.layout.simple_spinner_item, str);

sp1.setOnItemSelectedListener(new OnItemSelectedListener()
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long id) {
            // TODO Auto-generated method stub
            Toast.makeText(getBaseContext(), list.get(position), Toast.LENGTH_SHORT).show();

        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

sp2.setOnItemSelectedListener(new OnItemSelectedListener()
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long id) {
            // TODO Auto-generated method stub
            Toast.makeText(getBaseContext(), str[position], Toast.LENGTH_SHORT).show();

        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

You can also add spinner item value through String array xml file..

    <string name="app_name">Spinner_ex5</string>
    <string name="hello_world">Hello world!</string>
    <string name="menu_settings">Settings</string>
    <string name="title_activity_main">MainActivity</string>
    <string-array name="str2">
        <item>Data 1</item>
        <item>Data 2</item>
        <item>Data 3</item>
        <item>Data 4</item>
        <item>Data 5</item>


final Spinner sp3 = (Spinner) findViewById(;
ArrayAdapter<CharSequence> adp3 = ArrayAdapter.createFromResource(this,
                                    R.array.str2, android.R.layout.simple_list_item_1);

sp3.setOnItemSelectedListener(new OnItemSelectedListener()
        public void onItemSelected(AdapterView<?> arg0, View arg1, int position, long id) {
            // TODO Auto-generated method stub
            String ss = sp3.getSelectedItem().toString();
            Toast.makeText(getBaseContext(), ss, Toast.LENGTH_SHORT).show();

        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

SQL like search string starts with

COLLATE UTF8_GENERAL_CI will work as ignore-case. USE:

SELECT * from games WHERE title COLLATE UTF8_GENERAL_CI LIKE 'age of empires III%';


SELECT * from games WHERE LOWER(title) LIKE 'age of empires III%';

Formatting Phone Numbers in PHP

$data = '+11234567890';

if(  preg_match( '/^\+\d(\d{3})(\d{3})(\d{4})$/', $data,  $matches ) )
    $result = $matches[1] . '-' .$matches[2] . '-' . $matches[3];
    return $result;

What exactly is "exit" in PowerShell?

It's a reserved keyword (like return, filter, function, break).


Also, as per Section 7.6.4 of Bruce Payette's Powershell in Action:

But what happens when you want a script to exit from within a function defined in that script? ... To make this easier, Powershell has the exit keyword.

Of course, as other have pointed out, it's not hard to do what you want by wrapping exit in a function:

PS C:\> function ex{exit}
PS C:\> new-alias ^D ex

Change status bar text color to light in iOS 9 with Objective-C

First set

[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];

Go to your AppDelegate, find itsdidFinishLaunchingWithOptions method and do:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

[[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];


and then set View controller-based status bar appearance equal to NO in plist.

Intel HAXM installation error - This computer does not support Intel Virtualization Technology (VT-x)

In many cases some antivirus also start HyperV with window start and does not allow HAXM to install. I faced this issue because of AVAST antivirus. So I uninstalled AVAST, then HAXM installed properly after restart. Then I re-installed AVAST.

So its just a check while installing as now even with AVAST installed back, HAXM works properly with virtual box and android emulators.

Debugging "Element is not clickable at point" error

It's funny, all the time I spent looking at the various responses, no one had tried the obvious, which of course, I hadn't either. If your page has the same id used multiple times, as mine did, ("newButton",) and the one you want is not the first one found, then you will in all likelihood get this error. The easiest thing to do (C#):

var testIt = driver.FindElements(By.Id("newButton"));

Note it's FindElements, not FindElement.

And then test to see how many results came back from the retrieval. If it's the second one, you can then use:


Or get whomever reused ids to fix them.

How do I put an already-running process under nohup?

Unfortunately disown is specific to bash and not available in all shells.

Certain flavours of Unix (e.g. AIX and Solaris) have an option on the nohup command itself which can be applied to a running process:

nohup -p pid


How to name variables on the fly?

Use assign:

assign(paste("orca", i, sep = ""), list_name[[i]])

How to pick an image from gallery (SD Card) for my app?

For some reasons, all of the answers in this thread, in onActivityResult() try to post-process the received Uri, like getting the real path of the image and then use BitmapFactory.decodeFile(path) to get the Bitmap.

This step is unnecessary. The ImageView class has a method called setImageURI(uri). Pass your uri to it and you should be done.

Uri imageUri = data.getData();

For a complete working example you could take a look here:

Getting the Bitmap in a separate variable would make sense in cases where the image to be loaded is too large to fit in memory, and a scale down operation is necessary to prevent OurOfMemoryError, like shown in the @siamii answer.

How to elegantly check if a number is within a range?

Just to add to the noise here, you could create an extension method:

public static bool IsWithin(this int value, int minimum, int maximum)
    return value >= minimum && value <= maximum;

Which would let you do something like...

int val = 15;

bool foo = val.IsWithin(5,20);

That being said, this seems like a silly thing to do when the check itself is only one line.

Delaying function in swift

For adding argument to delay function.

First setup a dictionary then add it as the userInfo. Unwrap the info with the timer as the argument.

let arg : Int = 42
let infoDict : [String : AnyObject] = ["argumentInt", arg]

NSTimer.scheduledTimerWithTimeInterval(NSTimeInterval(3), target: self, selector: "functionHereWithArgument:", userInfo: infoDict, repeats: false)

Then in the called function

func functionHereWithArgument (timer : NSTimer)
    if let userInfo = timer.userInfo as? Dictionary<String, AnyObject>
         let argumentInt : Int = (userInfo[argumentInt] as! Int)

What is a good way to handle exceptions when trying to read a file in python?

How about this:

    f = open(fname, 'rb')
except OSError:
    print "Could not open/read file:", fname

with f:
    reader = csv.reader(f)
    for row in reader:
        pass #do stuff here

Function that creates a timestamp in c#

I always use something like the following:

public static String GetTimestamp(this DateTime value)
    return value.ToString("yyyyMMddHHmmssfff");

This will give you a string like 200905211035131468, as the string goes from highest order bits of the timestamp to lowest order simple string sorting in your SQL queries can be used to order by date if you're sticking values in a database

Error in Chrome only: XMLHttpRequest cannot load file URL No 'Access-Control-Allow-Origin' header is present on the requested resource

add this at the top of file,

header('content-type: application/json; charset=utf-8');
header("access-control-allow-origin: *");

Cannot make Project Lombok work on Eclipse

I had similar issue on MacBook Pro, I just followed the below link and issue got resolved.

Steps followed:-

  • Download the lombok.jar
  • Double click on this jar
  • This jar will try to find the eclipse installed on the machine, but in my case it was not able to identify the eclipse though I installed on it, this could be due to softlink to the eclipse path.
  • I just specified the location of the eclipse ini file by clicking "Specify location" button
  • This jar automatically updated the entry in eclipse.ini file for javaagent
    • I added the same jar to the classpath of the project in the eclipse
    • Restarted my eclipse

How to install easy_install in Python 2.7.1 on Windows 7

Look for the official 2.7 setuptools installer (which contains easy_install). You only need to install from sources for windows 64 bits.

Autoincrement VersionCode with gradle extra properties

Recently I was working on a gradle plugin for Android that makes generating versionCode and versionName automatically. there are lots of customization. here you can find more info about it

Programmatically navigate to another view controller/scene

See mine.

func actioncall () {
    let loginPageView = self.storyboard?.instantiateViewControllerWithIdentifier("LoginPageID") as! ViewController
    self.navigationController?.pushViewController(loginPageView, animated: true)

If you use presenting style, you might lose the page's navigation bar with preset pushnavigation.

Submitting the value of a disabled input field

you can also use the Readonly attribute: the input is not gonna be grayed but it won't be editable

<input type="text" name="lat" value="22.2222" readonly="readonly" />

How to test my servlet using JUnit

Another approach would be to create an embedded server to "host" your servlet, allowing you to write calls against it with libraries meant to make calls to actual servers (the usefulness of this approach somewhat depends on how easily you can make "legitimate" programatic calls to the server - I was testing a JMS (Java Messaging Service) access point, for which clients abound).

There are a couple of different routes you can go - the usual two are tomcat and jetty.

Warning: something to be mindful of when choosing the server to embed is the version of servlet-api you are using (the library which provides classes like HttpServletRequest). If you are using 2.5, I found Jetty 6.x to work well (which is the example I'll give below). If you're using servlet-api 3.0, the tomcat-7 embedded stuff seems to be a good option, however I had to abandon my attempt to use it, as the application I was testing used servlet-api 2.5. Trying to mix the two will result in NoSuchMethod and other such exceptions when attempting to configure or start the server.

You can set up such a server like this (Jetty 6.1.26, servlet-api 2.5):

public void startServer(int port, Servlet yourServletInstance){
    Server server = new Server(port);
    Context root = new Context(server, "/", Context.SESSIONS);

    root.addServlet(new ServletHolder(yourServletInstance), "/servlet/context/path");

    //If you need the servlet context for anything, such as spring wiring, you coudl get it like this
    //ServletContext servletContext = root.getServletContext();


How to query values from xml nodes?

Try this:

SELECT RawXML.value('(/GrobXmlFile//Grob//ReportHeader//OrganizationReportReferenceIdentifier/node())[1]','varchar(50)') AS ReportIdentifierNumber,
       RawXML.value('(/GrobXmlFile//Grob//ReportHeader//OrganizationNumber/node())[1]','int') AS OrginazationNumber
FROM Batches

Capturing console output from a .NET application (C#)

Use ProcessInfo.RedirectStandardOutput to redirect the output when creating your console process.

Then you can use Process.StandardOutput to read the program output.

The second link has a sample code how to do it.

Using Cygwin to Compile a C program; Execution error

If you just do gcc program.c -o program -mno-cygwin it will compile just fine and you won't need to add cygwin1.dll to your path and you can just go ahead and distribute your executable to a computer which doesn't have cygwin installed and it will still run. Hope this helps

Spring Boot REST service exception handling

For REST controllers, I would recommend to use Zalando Problem Spring Web.

If Spring Boot aims to embed some auto-configuration, this library does more for exception handling. You just need to add the dependency:


And then define one or more advice traits for your exceptions (or use those provided by default)

public interface NotAcceptableAdviceTrait extends AdviceTrait {

    default ResponseEntity<Problem> handleMediaTypeNotAcceptable(
            final HttpMediaTypeNotAcceptableException exception,
            final NativeWebRequest request) {
        return Responses.create(Status.NOT_ACCEPTABLE, exception, request);


Then you can defined the controller advice for exception handling as:

class ExceptionHandling implements MethodNotAllowedAdviceTrait, NotAcceptableAdviceTrait {


Generate a random date between two other dates

  1. Convert your input dates to numbers (int, float, whatever is best for your usage)
  2. Choose a number between your two date numbers.
  3. Convert this number back to a date.

Many algorithms for converting date to and from numbers are already available in many operating systems.

WPF: Create a dialog / prompt

I just add a static method to call it like a MessageBox:

<Window xmlns=""
<StackPanel Margin="5">
    <TextBlock Name="txtQuestion" Margin="5"/>
    <TextBox Name="txtResponse" Margin="5"/>
    <PasswordBox Name="txtPasswordResponse" />
    <StackPanel Orientation="Horizontal" Margin="5" HorizontalAlignment="Right">
        <Button Content="_Ok" IsDefault="True" Margin="5" Name="btnOk" Click="btnOk_Click" />
        <Button Content="_Cancel" IsCancel="True" Margin="5" Name="btnCancel" Click="btnCancel_Click" />

And the code behind:

public partial class PromptDialog : Window
    public enum InputType

    private InputType _inputType = InputType.Text;

    public PromptDialog(string question, string title, string defaultValue = "", InputType inputType = InputType.Text)
        this.Loaded += new RoutedEventHandler(PromptDialog_Loaded);
        txtQuestion.Text = question;
        Title = title;
        txtResponse.Text = defaultValue;
        _inputType = inputType;
        if (_inputType == InputType.Password)
            txtResponse.Visibility = Visibility.Collapsed;
            txtPasswordResponse.Visibility = Visibility.Collapsed;

    void PromptDialog_Loaded(object sender, RoutedEventArgs e)
        if (_inputType == InputType.Password)

    public static string Prompt(string question, string title, string defaultValue = "", InputType inputType = InputType.Text)
        PromptDialog inst = new PromptDialog(question, title, defaultValue, inputType);
        if (inst.DialogResult == true)
            return inst.ResponseText;
        return null;

    public string ResponseText
            if (_inputType == InputType.Password)
                return txtPasswordResponse.Password;
                return txtResponse.Text;

    private void btnOk_Click(object sender, RoutedEventArgs e)
        DialogResult = true;

    private void btnCancel_Click(object sender, RoutedEventArgs e)

So you can call it like:

string repeatPassword = PromptDialog.Prompt("Repeat password", "Password confirm", inputType: PromptDialog.InputType.Password);

How can I convert a DateTime to an int?

I think you want (this won't fit in a int though, you'll need to store it as a long):

long result = dateDate.Year * 10000000000 + dateDate.Month * 100000000 + dateDate.Day * 1000000 + dateDate.Hour * 10000 + dateDate.Minute * 100 + dateDate.Second;

Alternatively, storing the ticks is a better idea.

Copy / Put text on the clipboard with FireFox, Safari and Chrome

Firefox does allow you to store data in the clipboard, but due to security implications it is disabled by default. See how to enable it in "Granting JavaScript access to the clipboard" in the Mozilla Firefox knowledge base.

The solution offered by amdfan is the best if you are having a lot of users and configuring their browser isn't an option. Though you could test if the clipboard is available and provide a link for changing the settings, if the users are tech savvy. The JavaScript editor TinyMCE follows this approach.

Assembly Language - How to do Modulo?

An easy way to see what a modulus operator looks like on various architectures is to use the Godbolt Compiler Explorer.

Restarting cron after changing crontab file?

Ubuntu 18.04 * Usage: /etc/init.d/cron {start|stop|status|restart|reload|force-reload}

How to get URL parameter using jQuery or plain JavaScript?

use this

$.urlParam = function(name) {
  var results = new RegExp('[\?&amp;]' + name + '=([^&amp;#]*)').exec(window.location.href);
  return results[1] || 0;

How does a PreparedStatement avoid or prevent SQL injection?

Prepared statement is more secure. It will convert a parameter to the specified type.

For example stmt.setString(1, user); will convert the user parameter to a String.

Suppose that the parameter contains a SQL string containing an executable command: using a prepared statement will not allow that.

It adds metacharacter (a.k.a. auto conversion) to that.

This makes it is more safe.

What is the difference between XML and XSD?

XML has a much wider application than f.ex. HTML. It doesn't have an intrinsic, or default "application". So, while you might not really care that web pages are also governed by what's allowed, from the author's side, you'll probably want to precisely define what an XML document may and may not contain.

It's like designing a database.

The thing about XML technologies is that they are textual in nature. With XSD, it means you have a data structure definition framework that can be "plugged in" to text processing tools like PHP. So not only can you manipulate the data itself, but also very easily change and document the structure, and even auto-generate front-ends.

Viewed like this, XSD is the "glue" or "middleware" between data (XML) and data-processing tools.

How to get the day name from a selected date?

//default locale
//localized version

To make the answer more complete:

How do I change the background color of the ActionBar of an ActionBarActivity using XML?

I had the same problem, where my Action Bar would turn grey when I entered that code. Chances are your original style sheet looked like this:

<style name="AppBaseTheme" parent="android:Theme.Holo.Light.DarkActionBar">
    <!-- API 14 theme customizations can go here. -->

The "DarkActionBar" was what was keeping your Action Bar grey. I changed it to this, and it worked:

<style name="AppBaseTheme" parent="android:Theme.Holo.Light">
    <!-- API 14 theme customizations can go here. -->
    <item name="android:actionBarStyle">@style/MyActionBar</item>

<style name="MyActionBar" parent="@android:style/Widget.Holo.Light.ActionBar">
    <item name="android:background">#2aa4cd</item>
    <item name="android:titleTextStyle">@style/Theme.MyAppTheme.ActionBar.TitleTextStyle</item>

<style name="Theme.MyAppTheme.ActionBar.TitleTextStyle" parent="android:style/TextAppearance.Holo.Widget.ActionBar.Title">
    <item name="android:textColor">#FFFFFF</item>

I also threw in how to edit the text color. Also, no need to change anything surrounding the resources.


How do I get indices of N maximum values in a NumPy array?

For multidimensional arrays you can use the axis keyword in order to apply the partitioning along the expected axis.

# For a 2D array
indices = np.argpartition(arr, -N, axis=1)[:, -N:]

And for grabbing the items:

x = arr.shape[0]
arr[np.repeat(np.arange(x), N), indices.ravel()].reshape(x, N)

But note that this won't return a sorted result. In that case you can use np.argsort() along the intended axis:

indices = np.argsort(arr, axis=1)[:, -N:]

# Result
x = arr.shape[0]
arr[np.repeat(np.arange(x), N), indices.ravel()].reshape(x, N)

Here is an example:

In [42]: a = np.random.randint(0, 20, (10, 10))

In [44]: a
array([[ 7, 11, 12,  0,  2,  3,  4, 10,  6, 10],
       [16, 16,  4,  3, 18,  5, 10,  4, 14,  9],
       [ 2,  9, 15, 12, 18,  3, 13, 11,  5, 10],
       [14,  0,  9, 11,  1,  4,  9, 19, 18, 12],
       [ 0, 10,  5, 15,  9, 18,  5,  2, 16, 19],
       [14, 19,  3, 11, 13, 11, 13, 11,  1, 14],
       [ 7, 15, 18,  6,  5, 13,  1,  7,  9, 19],
       [11, 17, 11, 16, 14,  3, 16,  1, 12, 19],
       [ 2,  4, 14,  8,  6,  9, 14,  9,  1,  5],
       [ 1, 10, 15,  0,  1,  9, 18,  2,  2, 12]])

In [45]: np.argpartition(a, np.argmin(a, axis=0))[:, 1:] # 1 is because the first item is the minimum one.
array([[4, 5, 6, 8, 0, 7, 9, 1, 2],
       [2, 7, 5, 9, 6, 8, 1, 0, 4],
       [5, 8, 1, 9, 7, 3, 6, 2, 4],
       [4, 5, 2, 6, 3, 9, 0, 8, 7],
       [7, 2, 6, 4, 1, 3, 8, 5, 9],
       [2, 3, 5, 7, 6, 4, 0, 9, 1],
       [4, 3, 0, 7, 8, 5, 1, 2, 9],
       [5, 2, 0, 8, 4, 6, 3, 1, 9],
       [0, 1, 9, 4, 3, 7, 5, 2, 6],
       [0, 4, 7, 8, 5, 1, 9, 2, 6]])

In [46]: np.argpartition(a, np.argmin(a, axis=0))[:, -3:]
array([[9, 1, 2],
       [1, 0, 4],
       [6, 2, 4],
       [0, 8, 7],
       [8, 5, 9],
       [0, 9, 1],
       [1, 2, 9],
       [3, 1, 9],
       [5, 2, 6],
       [9, 2, 6]])

In [89]: a[np.repeat(np.arange(x), 3), ind.ravel()].reshape(x, 3)
array([[10, 11, 12],
       [16, 16, 18],
       [13, 15, 18],
       [14, 18, 19],
       [16, 18, 19],
       [14, 14, 19],
       [15, 18, 19],
       [16, 17, 19],
       [ 9, 14, 14],
       [12, 15, 18]])

MySQL "NOT IN" query

The subquery option has already been answered, but note that in many cases a LEFT JOIN can be a faster way to do this:

SELECT table1.*
FROM table1 LEFT JOIN table2 ON table2.principal=table1.principal
WHERE table2.principal IS NULL

If you want to check multiple tables to make sure it's not present in any of the tables (like in SRKR's comment), you can use this:

SELECT table1.*
FROM table1

ggplot combining two plots from different data.frames

You can take this trick to use only qplot. Use inner variable $mapping. You can even add colour= to your plots so this will be putted in mapping too, and then your plots combined with legend and colors automatically.

cpu_metric2 <- qplot(y=Y2,x=X1) 

cpu_metric1 <- qplot(y=Y1, 
                    xlab="Time", ylab="%") 

combined_cpu_plot <- cpu_metric1 + 
  geom_line() +

AssertContains on strings in jUnit

Example (junit version- 4.13)

import static org.assertj.core.api.Assertions.assertThat;
import org.junit.Test;

public class TestStr {

public void testThatStringIsContained(){
    String testStr = "hi,i am a test string";


What does -1 mean in numpy reshape?


check the below link for more info.

for the below example you mentioned the output explains the resultant vector to be a single row.(-1) indicates the number of rows to be 1. if the

a = numpy.matrix([[1, 2, 3, 4], [5, 6, 7, 8]])
b = numpy.reshape(a, -1)


matrix([[1, 2, 3, 4, 5, 6, 7, 8]])

this can be explained more precisely with another example:

b = np.arange(10).reshape((-1,1))

output:(is a 1 dimensional columnar array)



b = np.arange(10).reshape((1,-1))

output:(is a 1 dimensional row array)

array([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]])

CHECK constraint in MySQL is not working

As mentioned by joanq MariaDB now seems to support CHECK constraints among other goodies:

"Support for CHECK CONSTRAINT (MDEV-7563)."

HTML Canvas Full Screen

Well, I was looking to make my canvas fullscreen too, This is how i did it. I'll post the entire index.html since I am not a CSS expert yet : (basically just using position:fixed and width and height as 100% and top and left as 0% and i nested this CSS code for every tag. I also have min-height and min-width as 100%. When I tried it with a 1px border the border size was changing as I zoomed in and out but the canvas remained fullscreen.)

<!DOCTYPE html>_x000D_
<html style="position:fixed;min-height:100%;min-width:100%;height:100%;width:100%;top:0%;left:0%;resize:none;">_x000D_
<script "text/javascript" src="main.js"></script>_x000D_
<body id="BODY_CONTAINER" style="position:fixed;min-height:100%;min-width:100%;height:100%;width:100%;top:0%;left:0%;resize:none;">_x000D_
<div id="DIV_GUI_CONTAINER" style="position:fixed;min-height:100%;min-width:100%;height:100%;width:100%;top:0%;left:0%;resize:none;">_x000D_
<canvas id="myCanvas"  style="position:fixed;min-height:100%;min-width:100%;height:100%;width:100%;top:0%;left:0%;resize:none;">_x000D_

EDIT: add this to the canvas element:

<canvas id="myCanvas" width="" height="" style="position:fixed;min-height:100%;min-width:100%;height:100%;width:100%;top:0%;left:0%;resize:none;">_x000D_

add this to the javascript

canvas.width = window.screen.width;

canvas.height = window.screen.height;

I found this made the drawing a lot smoother than my original comment.


The network path was not found

Possibly also check the sessionState tag in Web.config

Believe it or not, some projects I've worked on will set a connection string here as well.

Setting this config to:

<sessionState mode="InProc" />

Fixed this issue in my case after checking all other connection strings were correct.

Can I concatenate multiple MySQL rows into one field?

In my case I had a row of Ids, and it was neccessary to cast it to char, otherwise, the result was encoded into binary format :


Using current time in UTC as default value in PostgreSQL

What about


If your other timestamp are without time zone then this cast will yield the matching type "timestamp without time zone" for the current time.

I would like to read what others think about that option, though. I still don't trust in my understanding of this "with/without" time zone stuff.

EDIT: Adding Michael Ekoka's comment here because it clarifies an important point:

Caveat. The question is about generating default timestamp in UTC for a timestamp column that happens to not store the time zone (perhaps because there's no need to store the time zone if you know that all your timestamps share the same). What your solution does is to generate a local timestamp (which for most people will not necessarily be set to UTC) and store it as a naive timestamp (one that does not specify its time zone).

Error - is not marked as serializable

If you store an object in session state, that object must be serializable.


In order for the session to be serialized correctly, all objects the application stores as session attributes must declare the [Serializable] attribute. Additionally, if the object requires custom serialization methods, it must also implement the ISerializable interface.

HTML-encoding lost when attribute read from input field

For those who prefer plain javascript, here is the method I have used successfully:

function escapeHTML (str)
    var div = document.createElement('div');
    var text = document.createTextNode(str);
    return div.innerHTML;

Webview load html from assets directory

Whenever you are creating activity, you must add setcontentview(your layout) after super call. Because setcontentview bind xml into your activity so that's the reason you are getting nullpointerexception.

 webView = (WebView) findViewById(;

html script src="" triggering redirection with button

First you are linking the file that is here:

<script src="../Script/login.js"> 

Which would lead the website to a file in the Folder Script, but then in the second paragraph you are saying that the folder name is

and also i have onother folder named scripts that contains the the following login.js file

So, this won't work! Because you are not accessing the correct file. To do that please write the code as

<script src="/script/login.js"></script>

Try removing the .. from the beginning of the code too.

This way, you'll reach the js file where the function would run!

Just to make sure:

Just to make sure that the files are attached the HTML DOM, then please open Developer Tools (F12) and in the network workspace note each request that the browser makes to the server. This way you will learn which files were loaded and which weren't, and also why they were not!

Good luck.

How to start a Process as administrator mode in C#

 Process proc = new Process();                                                              
                   ProcessStartInfo info = 
                   new ProcessStartInfo("Your Process name".exe, "Arguments");
                   info.WindowStyle = ProcessWindowStyle.Hidden;
                   info.UseShellExecute =true;
                   info.Verb ="runas";
                   proc.StartInfo = info;

How to store standard error in a variable

For error proofing your commands:


execute () {
    error=$(eval "${command}" 2>&1 >"/dev/null")

    if [ ${?} -ne 0 ]; then
        echo "${function}: ${error}"
        exit 1

Inspired in Lean manufacturing:

Difference between \w and \b regular expression meta characters

\w is not a word boundary, it matches any word character, including underscores: [a-zA-Z0-9_]. \b is a word boundary, that is, it matches the position between a word and a non-alphanumeric character: \W or [^\w].

These implementations may vary from language to language though.

Alternative for frames in html5 using iframes

HTML 5 does support iframes. There were a few interesting attributes added like "sandbox" and "srcdoc".

or you can use

<object data="framed.html" type="text/html"><p>This is the fallback code!</p></object>

How to detect when a UIScrollView has finished scrolling

I only just found this question, which is pretty much the same I asked: How to know exactly when a UIScrollView's scrolling has stopped?

Though didEndDecelerating works when scrolling, panning with stationary release does not register.

I eventually found a solution. didEndDragging has a parameter WillDecelerate, which is false in the stationary release situation.

By checking for !decelerate in DidEndDragging, combined with didEndDecelerating, you get both situations that are the end of scrolling.

How to display two digits after decimal point in SQL Server

want to convert the column name Amount as float number with 2 decimals

CASE WHEN EXISTS (SELECT Amount From InvoiceFee Ifee WHERE IFEE.InvoiceId = 
DIR.InvoiceId AND FeeId = 'Freight Cost')
     THEN  CAST ((SELECT Amount From InvoiceFee Ifee WHERE IFEE.InvoiceId = 
DIR.InvoiceId AND FeeId = 'Freight Cost') AS VARCHAR)
            ELSE '' END AS FCost,

How can I create a table with borders in Android?

enter image description here

Here i have designed the list by the following design image. My listitem filename is Propertylistitem.xml and cellborder.xml is used drawable shape for the cellborder output, are show in this image. necessary code i added here.


<TableLayout... >
            <TableRow... >
                 <TextView ...

            <TableRow... >

filename:cellborder.xml Here i just want only border in my design, so i put comment the solid color tag.

<?xml version="1.0" encoding="utf-8"?>
    <shape xmlns:android="" android:shape="rectangle" >
    <!--     <solid android:color="#dc6888"/>     -->
        <stroke android:width="0.1dp" android:color="#ffffff"
        <padding android:left="0dp" android:top="0dp"
                android:right="0dp" android:bottom="0dp" />

How to create a numpy array of arbitrary length strings?

You can do so by creating an array of dtype=object. If you try to assign a long string to a normal numpy array, it truncates the string:

>>> a = numpy.array(['apples', 'foobar', 'cowboy'])
>>> a[2] = 'bananas'
>>> a
array(['apples', 'foobar', 'banana'], 

But when you use dtype=object, you get an array of python object references. So you can have all the behaviors of python strings:

>>> a = numpy.array(['apples', 'foobar', 'cowboy'], dtype=object)
>>> a
array([apples, foobar, cowboy], dtype=object)
>>> a[2] = 'bananas'
>>> a
array([apples, foobar, bananas], dtype=object)

Indeed, because it's an array of objects, you can assign any kind of python object to the array:

>>> a[2] = {1:2, 3:4}
>>> a
array([apples, foobar, {1: 2, 3: 4}], dtype=object)

However, this undoes a lot of the benefits of using numpy, which is so fast because it works on large contiguous blocks of raw memory. Working with python objects adds a lot of overhead. A simple example:

>>> a = numpy.array(['abba' for _ in range(10000)])
>>> b = numpy.array(['abba' for _ in range(10000)], dtype=object)
>>> %timeit a.copy()
100000 loops, best of 3: 2.51 us per loop
>>> %timeit b.copy()
10000 loops, best of 3: 48.4 us per loop

"Use of undeclared type" in Swift, even though type is internal, and exists in same module

In XCode menu Product->Clean and then Product->Build worked for me. I encountered this issue when added new ViewController to my project in new Group/Folder.

Is there a constraint that restricts my generic method to numeric types?

Beginning with C# 7.3, you can use closer approximation - the unmanaged constraint to specify that a type parameter is a non-pointer, non-nullable unmanaged type.

class SomeGeneric<T> where T : unmanaged

The unmanaged constraint implies the struct constraint and can't be combined with either the struct or new() constraints.

A type is an unmanaged type if it's any of the following types:

  • sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, or bool
  • Any enum type
  • Any pointer type
  • Any user-defined struct type that contains fields of unmanaged types only and, in C# 7.3 and earlier, is not a constructed type (a type that includes at least one type argument)

To restrict further and eliminate pointer and user-defined types that do not implement IComparable add IComparable (but enum is still derived from IComparable, so restrict enum by adding IEquatable < T >, you can go further depending on your circumstances and add additional interfaces. unmanaged allows to keep this list shorter):

    class SomeGeneric<T> where T : unmanaged, IComparable, IEquatable<T>

But this doesn't prevent from DateTime instantiation.

Maximum size for a SQL Server Query? IN clause? Is there a Better Approach

Can you load the GUIDs into a scratch table then do a

... WHERE var IN SELECT guid FROM #scratchtable

Errors: Data path ".builders['app-shell']" should have required property 'class'

I did this change in package.json file, then it works.

"@angular-devkit/build-angular": "^0.803.23"


"@angular-devkit/build-angular": "^0.13.9"

How can I make SMTP authenticated in C#

using System.Net;
using System.Net.Mail;

using(SmtpClient smtpClient = new SmtpClient())
    var basicCredential = new NetworkCredential("username", "password"); 
    using(MailMessage message = new MailMessage())
        MailAddress fromAddress = new MailAddress("[email protected]"); 

        smtpClient.Host = "";
        smtpClient.UseDefaultCredentials = false;
        smtpClient.Credentials = basicCredential;

        message.From = fromAddress;
        message.Subject = "your subject";
        // Set IsBodyHtml to true means you can send HTML email.
        message.IsBodyHtml = true;
        message.Body = "<h1>your message body</h1>";
        message.To.Add("[email protected]"); 

        catch(Exception ex)
            //Error, could not send the message

You may use the above code.

Transaction count after EXECUTE indicates a mismatching number of BEGIN and COMMIT statements. Previous count = 1, current count = 0

In my opinion the accepted answer is in most cases an overkill.

The cause of the error is often mismatch of BEGIN and COMMIT as clearly stated by the error. This means using:

    -- your query here

instead of

Begin Transaction
    -- your query here

omitting Transaction after Begin causes this error!

CSS3 Box Shadow on Top, Left, and Right Only

#div:before {

How to get a list of MySQL views?

The error your seeing is probably due to a non-MySQL created directory in MySQL's data directory. MySQL maps the database structure pretty directly onto the file system, databases are mapped to directories and tables are files in those directories.

The name of the non-working database looks suspiciously like someone has copied the mysql database directory to a backup at some point and left it in MySQL's data directory. This isn't a problem as long as you don't try and use the database for anything. Unfortunately the information schema scans all of the databases it finds and finds that this one isn't a real database and gets upset.

The solution is to find the mysql.bak directory on the hard disk and move it well away from MySQL.

What is the purpose of Order By 1 in SQL select statement?

This will sort your results by the first column returned. In the example it will sort by payment_date.

Capitalize first letter. MySQL

mysql> SELECT schedule_type AS Schedule FROM ad_campaign limit 1;
| Schedule |
1 row in set (0.00 sec)

mysql> SELECT CONCAT(UCASE(MID(schedule_type,1,1)),LCASE(MID(schedule_type,2))) AS Schedule FROM ad_campaign limit 1;
| Schedule |
| Enddate  |
1 row in set (0.00 sec)

How to print from Flask @app.route to python console

I think the core issue with Flask is that stdout gets buffered. I was able to print with print('Hi', flush=True). You can also disable buffering by setting the PYTHONUNBUFFERED environment variable (to any non-empty string).

What is android:weightSum in android, and how does it work?

One thing which seems like no one else mentioned: let's say you have a vertical LinearLayout, so in order for the weights in layout/element/view inside it to work 100% properly - all of them must have layout_height property (which must exist in your xml file) set to 0dp. Seems like any other value would mess things up in some cases.

How do I request and receive user input in a .bat and use it to run a certain program?

I have improved batch file with yes or no prompt. If user enter any character except y and n , then it will again prompt user for valid input. It Works for me.

    @echo off

        set /P c= Are you sure want to contine (y/n)?

    if /I "%c%" EQU "Y" (
    goto :FnYes 
    ) else if /I "%c%" EQU "N" ( 
    goto :FnNo
    ) else ( 
    goto :InValid 

     echo You have entered Y
     goto :END

     echo You have entered N
     goto :END

     echo Invalid selection. Enter Y or N
     goto :ConfirmBox


/I in if condition will validate both lowercase and uppercase characters.

What regular expression will match valid international phone numbers?

This works for me, without 00, 001, 0011 etc prefix though:


Counting array elements in Python

The method len() returns the number of elements in the list.




myArray = [1, 2, 3]



Submit HTML form, perform javascript function (alert then redirect)

<form action="javascript:completeAndRedirect();">
    <input type="text" id="Edit1" 
    style="width:280; height:50; font-family:'Lucida Sans Unicode', 'Lucida Grande', sans-serif; font-size:22px">

Changing action to point at your function would solve the problem, in a different way.

Semaphore vs. Monitors - what's the difference?

One Line Answer:

Monitor: controls only ONE thread at a time can execute in the monitor. (need to acquire lock to execute the single thread)

Semaphore: a lock that protects a shared resource. (need to acquire the lock to access resource)

Get random integer in range (x, y]?

Random generator = new Random(); 
int i = generator.nextInt(10) + 1;

Using subprocess to run Python script on Windows

How about this:

import sys
import subprocess

theproc = subprocess.Popen("", shell = True)
theproc.communicate()                   # ^^^^^^^^^^^^

This tells subprocess to use the OS shell to open your script, and works on anything that you can just run in cmd.exe.

Additionally, this will search the PATH for "" - which could be desirable.

CSS3 transform: rotate; in IE9

I know this is old, but I was having this same issue, found this post, and while it didn't explain exactly what was wrong, it helped me to the right answer - so hopefully my answer helps someone else who might be having a similar problem to mine.

I had an element I wanted rotated vertical, so naturally I added the filter: for IE8 and then the -ms-transform property for IE9. What I found is that having the -ms-transform property AND the filter applied to the same element causes IE9 to render the element very poorly. My solution:

  1. If you are using the transform-origin property, add one for MS too (-ms-transform-origin: left bottom;). If you don't see your element, it could be that it's rotating on it's middle axis and thus leaving the page somehow - so double check that.

  2. Move the filter: property for IE7&8 to a separate style sheet and use an IE conditional to insert that style sheet for browsers less than IE9. This way it doesn't affect the IE9 styles and all should work fine.

  3. Make sure to use the correct DOCTYPE tag as well; if you have it wrong IE9 will not work properly.

Running JAR file on Windows 10

How do I run an executable JAR file? If you have a jar file called Example.jar, follow these rules:

Open a notepad.exe.
Write : java -jar Example.jar.
Save it with the extension .bat.
Copy it to the directory which has the .jar file.
Double click it to run your .jar file.

Concatenate chars to form String in java

You can use StringBuilder:

    StringBuilder sb = new StringBuilder();
    String str = sb.toString()

Or if you already have the characters, you can pass a character array to the String constructor:

String str = new String(new char[]{'a', 'b', 'c'});

Delete duplicate records from a SQL table without a primary key

Use the row number to differentiate between duplicate records. Keep the first row number for an EmpID/EmpSSN and delete the rest:

    DELETE FROM Employee a
                               FROM Employee b
                              WHERE a.EmpID  = b.EmpID
                                AND a.EmpSSN = b.EmpSSN )

Can typescript export a function?

It's hard to tell what you're going for in that example. exports = is about exporting from external modules, but the code sample you linked is an internal module.

Rule of thumb: If you write module foo { ... }, you're writing an internal module; if you write export something something at top-level in a file, you're writing an external module. It's somewhat rare that you'd actually write export module foo at top-level (since then you'd be double-nesting the name), and it's even rarer that you'd write module foo in a file that had a top-level export (since foo would not be externally visible).

The following things make sense (each scenario delineated by a horizontal rule):

// An internal module named SayHi with an exported function 'foo'
module SayHi {
    export function foo() {

    export class bar { }

// N.B. this line could be in another file that has a
// <reference> tag to the file that has 'module SayHi' in it;
var b = new;


// This *file* is an external module because it has a top-level 'export'
export function foo() {

export class bar { }


// This file is also an external module because it has an 'import' declaration
import f1 = module('file1');;
var b = new;


// This will only work in 0.9.0+. This file is an external
// module because it has a top-level 'export'
function f() { }
function g() { }
export = { alpha: f, beta: g };


// This file is also an external module because it has an 'import' declaration
import f1 = require('file1');
f1.alpha(); // invokes f
f1.beta(); // invokes g

checking if a number is divisible by 6 PHP

Simply run a while loop that will continue to loop (and increase the number) until the number is divisible by 6.

while ($number % 6 != 0) {

Add days to JavaScript Date

As simple as this:

new Date((new Date()).getTime() + (60*60*24*1000));

Update only specific fields in a models.Model

To update a subset of fields, you can use update_fields:["active"]) 

The update_fields argument was added in Django 1.5. In earlier versions, you could use the update() method instead:


How to view the SQL queries issued by JPA?

Logging options are provider-specific. You need to know which JPA implementation do you use.

  • Hibernate (see here):

    <property name = "hibernate.show_sql" value = "true" />
  • EclipseLink (see here):

    <property name="eclipselink.logging.level" value="FINE"/>
  • OpenJPA (see here):

    <property name="openjpa.Log" value="DefaultLevel=WARN,Runtime=INFO,Tool=INFO,SQL=TRACE"/>
  • DataNucleus (see here):

    Set the log category DataNucleus.Datastore.Native to a level, like DEBUG.

Populating a razor dropdownlist from a List<object> in MVC

Your call to DropDownListFor needs a few more parameters to flesh it out. You need a SelectList as in the following SO question:

MVC3 DropDownListFor - a simple example?

With what you have there, you've only told it where to store the data, not where to load the list from.

How to get setuptools and easy_install?

For Amazon Linux AMI

yum install -y python-setuptools 

Check if space is in a string

# The following would be a very simple solution.

string = input("Enter your string :")
noofspacesinstring = 0
for counter in string:
    if counter == " ":
       noofspacesinstring += 1
if noofspacesinstring == 0:
   message = "Your string is a single word" 
   message = "Your string is not a single word"

pop/remove items out of a python tuple

In Python 3 this is no longer an issue, and you really don't want to use list comprehension, coercion, filters, functions or lambdas for something like this.

Just use

popped = unpopped[:-1]

Remember that it's an immutable, so you will have to reassign the value if you want it to change

my_tuple = my_tuple[:-1]


>>> foo= 3,5,2,4,78,2,1
>>> foo
(3, 5, 2, 4, 78, 2, 1)
(3, 5, 2, 4, 78, 2)

Reference - What does this regex mean?

The Stack Overflow Regular Expressions FAQ

See also a lot of general hints and useful links at the tag details page.

Online tutorials


Character Classes

Escape Sequences


(Also see "Flavor-Specific Information ? Java ? The functions in Matcher")





Common Tasks

Advanced Regex-Fu

Flavor-Specific Information

(Except for those marked with *, this section contains non-Stack Overflow links.)

General information

(Links marked with * are non-Stack Overflow links.)

Examples of regex that can cause regex engine to fail

Tools: Testers and Explainers

(This section contains non-Stack Overflow links.)

SQL Server: Extract Table Meta-Data (description, fields and their data types)

If you simply want to view the information in a convenient way, Red Gate's SQL Prompt might help.

If you hover over the object text in a query window SQL Prompt will display the MS_Description extended property text in a tooltip. Clicking on the tooltip will open a dialog displaying the column information and also the object's DDL.

How to display alt text for an image in chrome

To display the Alt text of missing images, we have to add a style like this. I think, there is no need to add extra javascript for this.

.Your_Image_Class_Name {
  font-size: 14px;

It's work for me. Enjoy!!!!

How to allow all Network connection types HTTP and HTTPS in Android (9) Pie?

You may check if you are sending clearText through HTTP Fix :
In the Case of Apache HTTP client deprecation (From Google ) : With Android 6.0, we removed support for the Apache HTTP client. Beginning with Android 9, that library is removed from the bootclasspath and is not available to apps by default. To continue using the Apache HTTP client, apps that target Android 9 and above can add the following to their AndroidManifest.xml:


jQuery .ajax() POST Request throws 405 (Method Not Allowed) on RESTful WCF

For same error code i had quite different reason, I'm sharing here to help

I had web api action like below

public IHttpActionResult GetBooks (int id)

I changed the method to accept two parameters category and author so i changed the parameters as below, i also put the attribute [Httppost]

public IHttpActionResult GetBooks (int category, int author)

I also changed ajax options like below and at this point i start getting error 405 method not allowed

var options = {
    url: '/api/books/GetBooks',
    type: 'POST',
    dataType: 'json',
    cache: false,
    traditional: true, 
    data: {
        category: 1,
        author: 15

When i created class for web api action parameters like below error was gone

public class BookParam
    public int Category { get; set; }
    public int Author { get; set; }
public IHttpActionResult GetBooks (BookParam param)

angularjs getting previous route path

In your html :

<a href="javascript:void(0);" ng-click="go_back()">Go Back</a>

On your main controller :

$scope.go_back = function() { 

When user click on Go Back link the controller function is called and it will go back to previous route.

converting a base 64 string to an image and saving it

Here is working code for converting an image from a base64 string to an Image object and storing it in a folder with unique file name:

public void SaveImage()

    //this is a simple white background image
    var myfilename= string.Format(@"{0}", Guid.NewGuid());

    //Generate unique filename
    string filepath= "~/UserImages/" + myfilename+ ".jpeg";
    var bytess = Convert.FromBase64String(strm);
    using (var imageFile = new FileStream(filepath, FileMode.Create))
        imageFile.Write(bytess, 0, bytess.Length);

Returning http status code from Web Api controller

I know there are several good answers here but this is what I needed so I figured I'd add this code in case anyone else needs to return whatever status code and response body they wanted in 4.7.x with webAPI.

public class DuplicateResponseResult<TResponse> : IHttpActionResult
    private TResponse _response;
    private HttpStatusCode _statusCode;
    private HttpRequestMessage _httpRequestMessage;
    public DuplicateResponseResult(HttpRequestMessage httpRequestMessage, TResponse response, HttpStatusCode statusCode)
        _httpRequestMessage = httpRequestMessage;
        _response = response;
        _statusCode = statusCode;

    public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
        var response = new HttpResponseMessage(_statusCode);
        return Task.FromResult(_httpRequestMessage.CreateResponse(_statusCode, _response));

css to make bootstrap navbar transparent

<nav class="navbar navbar-expand-lg navbar-light fixed-top bg-transparent">
              <a class="navbar-brand" href="#">Navbar w/ text</a>
              <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarText" aria-controls="navbarText" aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
              <div class="collapse navbar-collapse" id="navbarText">
                <ul class="navbar-nav mr-auto">
                  <li class="nav-item active">
                    <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
                  <li class="nav-item">
                    <a class="nav-link" href="#">Features</a>
                  <li class="nav-item">
                    <a class="nav-link" href="#">Pricing</a>
                <span class="navbar-text">
                  Navbar text with an inline element

Converting bool to text in C++

As long as strings can be viewed directly as a char array it's going to be really hard to convince me that std::string represents strings as first class citizens in C++.

Besides, combining allocation and boundedness seems to be a bad idea to me anyways.

Can an abstract class have a constructor?

In order to achieve constructor chaining, the abstract class will have a constructor. The compiler keeps Super() statement inside the subclass constructor, which will call the superclass constructor. If there were no constructors for abstract classes then java rules are violated and we can't achieve constructor chaining.

Is this very likely to create a memory leak in Tomcat?

Sometimes this has to do with configuration changes. When we upgraded from Tomncat 6.0.14 to 6.0.26, we had seen something similar. here is the solution

Predict() - Maybe I'm not understanding it

Thanks Hong, that was exactly the problem I was running into. The error you get suggests that the number of rows is wrong, but the problem is actually that the model has been trained using a command that ends up with the wrong names for parameters.

This is really a critical detail that is entirely non-obvious for lm and so on. Some of the tutorial make reference to doing lines like lm(olive$Area@olive$Palmitic) - ending up with variable names of olive$Area NOT Area, so creating an entry using anewdata<-data.frame(Palmitic=2) can't then be used. If you use lm(Area@Palmitic,data=olive) then the variable names are right and prediction works.

The real problem is that the error message does not indicate the problem at all:

Warning message: 'anewdata' had 1 rows but variable(s) found to have X rows

Missing styles. Is the correct theme chosen for this layout?

In my case the problem occurred while the default setting for Android Version in the Designer was set to 'Preview N'. Changed Android Version to '23' and the error notification went away.
And don't forget to uncheck 'Automatically Pick Best'.

How to force Sequential Javascript Execution?

I am back to this questions after all this time because it took me that long to find what I think is a clean solution : The only way to force a javascript sequential execution that I know of is to use promises. There are exhaustive explications of promises at : Promises/A and Promises/A+

The only library implementing promises I know is jquery so here is how I would solve the question using jquery promises :

    <script src=""></script>
    <script type="text/javascript">
    function myfunction()
        promise = longfunctionfirst().then(shortfunctionsecond);
    function longfunctionfirst()
        d = new $.Deferred();
        setTimeout('alert("first function finished");d.resolve()',3000);
        return d.promise()
    function shortfunctionsecond()
        d = new $.Deferred();
        setTimeout('alert("second function finished");d.resolve()',200);
        return d.promise()
    <a href="#" onclick="javascript:myfunction();return false;">Call my function</a>

By implementing a promise and chaining the functions with .then() you ensure that the second function will be executed only after the first one has executed It is the command d.resolve() in longfunctionfirst() that give the signal to start the next function.

Technically the shortfunctionsecond() does not need to create a deferred and return a promise, but I fell in love with promises and tend to implement everything with promises, sorry.

Display SQL query results in php

You need to fetch the data from each row of the resultset obtained from the query. You can use mysql_fetch_array() for this.

// Process all rows
while($row = mysql_fetch_array($result)) {
    echo $row['column_name']; // Print a single column data
    echo print_r($row);       // Print the entire row data

Change your code to this :

$sql="SELECT * FROM  modul1open WHERE idM1O>=(SELECT FLOOR( MAX( idM1O ) * RAND( ) )  FROM  modul1open) 

$result = mysql_query($sql);
while($row = mysql_fetch_array($result)) {
    echo $row['fieldname']; 

How to decrypt an encrypted Apple iTunes iPhone backup?

Security researchers Jean-Baptiste Bédrune and Jean Sigwald presented how to do this at Hack-in-the-box Amsterdam 2011.

Since then, Apple has released an iOS Security Whitepaper with more details about keys and algorithms, and Charlie Miller et al. have released the iOS Hacker’s Handbook, which covers some of the same ground in a how-to fashion. When iOS 10 first came out there were changes to the backup format which Apple did not publicize at first, but various people reverse-engineered the format changes.

Encrypted backups are great

The great thing about encrypted iPhone backups is that they contain things like WiFi passwords that aren’t in regular unencrypted backups. As discussed in the iOS Security Whitepaper, encrypted backups are considered more “secure,” so Apple considers it ok to include more sensitive information in them.

An important warning: obviously, decrypting your iOS device’s backup removes its encryption. To protect your privacy and security, you should only run these scripts on a machine with full-disk encryption. While it is possible for a security expert to write software that protects keys in memory, e.g. by using functions like VirtualLock() and SecureZeroMemory() among many other things, these Python scripts will store your encryption keys and passwords in strings to be garbage-collected by Python. This means your secret keys and passwords will live in RAM for a while, from whence they will leak into your swap file and onto your disk, where an adversary can recover them. This completely defeats the point of having an encrypted backup.

How to decrypt backups: in theory

The iOS Security Whitepaper explains the fundamental concepts of per-file keys, protection classes, protection class keys, and keybags better than I can. If you’re not already familiar with these, take a few minutes to read the relevant parts.

Now you know that every file in iOS is encrypted with its own random per-file encryption key, belongs to a protection class, and the per-file encryption keys are stored in the filesystem metadata, wrapped in the protection class key.

To decrypt:

  1. Decode the keybag stored in the BackupKeyBag entry of Manifest.plist. A high-level overview of this structure is given in the whitepaper. The iPhone Wiki describes the binary format: a 4-byte string type field, a 4-byte big-endian length field, and then the value itself.

    The important values are the PBKDF2 ITERations and SALT, the double protection salt DPSL and iteration count DPIC, and then for each protection CLS, the WPKY wrapped key.

  2. Using the backup password derive a 32-byte key using the correct PBKDF2 salt and number of iterations. First use a SHA256 round with DPSL and DPIC, then a SHA1 round with ITER and SALT.

    Unwrap each wrapped key according to RFC 3394.

  3. Decrypt the manifest database by pulling the 4-byte protection class and longer key from the ManifestKey in Manifest.plist, and unwrapping it. You now have a SQLite database with all file metadata.

  4. For each file of interest, get the class-encrypted per-file encryption key and protection class code by looking in the Files.file database column for a binary plist containing EncryptionKey and ProtectionClass entries. Strip the initial four-byte length tag from EncryptionKey before using.

    Then, derive the final decryption key by unwrapping it with the class key that was unwrapped with the backup password. Then decrypt the file using AES in CBC mode with a zero IV.

How to decrypt backups: in practice

First you’ll need some library dependencies. If you’re on a mac using a homebrew-installed Python 2.7 or 3.7, you can install the dependencies with:

CFLAGS="-I$(brew --prefix)/opt/openssl/include" \
LDFLAGS="-L$(brew --prefix)/opt/openssl/lib" \    
    pip install biplist fastpbkdf2 pycrypto

In runnable source code form, here is how to decrypt a single preferences file from an encrypted iPhone backup:

#!/usr/bin/env python3.7
# coding: UTF-8

from __future__ import print_function
from __future__ import division

import argparse
import getpass
import os.path
import pprint
import random
import shutil
import sqlite3
import string
import struct
import tempfile
from binascii import hexlify

import Crypto.Cipher.AES #
import biplist
import fastpbkdf2
from biplist import InvalidPlistException

def main():
    ## Parse options
    parser = argparse.ArgumentParser()
    parser.add_argument('--backup-directory', dest='backup_directory',
    parser.add_argument('--password-pipe', dest='password_pipe',
Keeps password from being visible in system process list.
Typical use: --password-pipe=<(echo -n foo)
    parser.add_argument('--no-anonymize-output', dest='anonymize',
    args = parser.parse_args()
    ANONYMIZE_OUTPUT = args.anonymize
        print('Warning: All output keys are FAKE to protect your privacy')

    manifest_file = os.path.join(args.backup_directory, 'Manifest.plist')
    with open(manifest_file, 'rb') as infile:
        manifest_plist = biplist.readPlist(infile)
    keybag = Keybag(manifest_plist['BackupKeyBag'])
    # the actual keys are unknown, but the wrapped keys are known

    if args.password_pipe:
        password = readpipe(args.password_pipe)
        if password.endswith(b'\n'):
            password = password[:-1]
        password = getpass.getpass('Backup password: ').encode('utf-8')

    ## Unlock keybag with password
    if not keybag.unlockWithPasscode(password):
        raise Exception('Could not unlock keybag; bad password?')
    # now the keys are known too

    ## Decrypt metadata DB
    manifest_key = manifest_plist['ManifestKey'][4:]
    with open(os.path.join(args.backup_directory, 'Manifest.db'), 'rb') as db:
        encrypted_db =

    manifest_class = struct.unpack('<l', manifest_plist['ManifestKey'][:4])[0]
    key = keybag.unwrapKeyForClass(manifest_class, manifest_key)
    decrypted_data = AESdecryptCBC(encrypted_db, key)

    temp_dir = tempfile.mkdtemp()
        # Does anyone know how to get Python’s SQLite module to open some
        # bytes in memory as a database?
        db_filename = os.path.join(temp_dir, 'db.sqlite3')
        with open(db_filename, 'wb') as db_file:
        conn = sqlite3.connect(db_filename)
        conn.row_factory = sqlite3.Row
        c = conn.cursor()
        # c.execute("select * from Files limit 1");
        # r = c.fetchone()
            SELECT fileID, domain, relativePath, file
            FROM Files
            WHERE relativePath LIKE 'Media/PhotoData/MISC/DCIM_APPLE.plist'
            ORDER BY domain, relativePath""")
        results = c.fetchall()

    for item in results:
        fileID, domain, relativePath, file_bplist = item

        plist = biplist.readPlistFromString(file_bplist)
        file_data = plist['$objects'][plist['$top']['root'].integer]
        size = file_data['Size']

        protection_class = file_data['ProtectionClass']
        encryption_key = plist['$objects'][

        backup_filename = os.path.join(args.backup_directory,
                                    fileID[:2], fileID)
        with open(backup_filename, 'rb') as infile:
            data =
            key = keybag.unwrapKeyForClass(protection_class, encryption_key)
            # truncate to actual length, as encryption may introduce padding
            decrypted_data = AESdecryptCBC(data, key)[:size]

        print('== decrypted data:')

        print('== pretty-printed plist')

# this section is mostly copied from parts of iphone-dataprotection

KEYBAG_TYPES = ["System", "Backup", "Escrow", "OTA (icloud)"]
KEY_TYPES = ["AES", "Curve25519"]

    6: "kSecAttrAccessibleWhenUnlocked",
    7: "kSecAttrAccessibleAfterFirstUnlock",
    8: "kSecAttrAccessibleAlways",
    9: "kSecAttrAccessibleWhenUnlockedThisDeviceOnly",
    10: "kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly",
    11: "kSecAttrAccessibleAlwaysThisDeviceOnly"

class Keybag(object):
    def __init__(self, data):
        self.type = None
        self.uuid = None
        self.wrap = None
        self.deviceKey = None
        self.attrs = {}
        self.classKeys = {}
        self.KeyBagKeys = None #DATASIGN blob

    def parseBinaryBlob(self, data):
        currentClassKey = None

        for tag, data in loopTLVBlocks(data):
            if len(data) == 4:
                data = struct.unpack(">L", data)[0]
            if tag == b"TYPE":
                self.type = data
                if self.type > 3:
                    print("FAIL: keybag type > 3 : %d" % self.type)
            elif tag == b"UUID" and self.uuid is None:
                self.uuid = data
            elif tag == b"WRAP" and self.wrap is None:
                self.wrap = data
            elif tag == b"UUID":
                if currentClassKey:
                    self.classKeys[currentClassKey[b"CLAS"]] = currentClassKey
                currentClassKey = {b"UUID": data}
            elif tag in CLASSKEY_TAGS:
                currentClassKey[tag] = data
                self.attrs[tag] = data
        if currentClassKey:
            self.classKeys[currentClassKey[b"CLAS"]] = currentClassKey

    def unlockWithPasscode(self, passcode):
        passcode1 = fastpbkdf2.pbkdf2_hmac('sha256', passcode,
                                        self.attrs[b"DPIC"], 32)
        passcode_key = fastpbkdf2.pbkdf2_hmac('sha1', passcode1,
                                            self.attrs[b"ITER"], 32)
        print('== Passcode key')
        for classkey in self.classKeys.values():
            if b"WPKY" not in classkey:
            k = classkey[b"WPKY"]
            if classkey[b"WRAP"] & WRAP_PASSCODE:
                k = AESUnwrap(passcode_key, classkey[b"WPKY"])
                if not k:
                    return False
                classkey[b"KEY"] = k
        return True

    def unwrapKeyForClass(self, protection_class, persistent_key):
        ck = self.classKeys[protection_class][b"KEY"]
        if len(persistent_key) != 0x28:
            raise Exception("Invalid key length")
        return AESUnwrap(ck, persistent_key)

    def printClassKeys(self):
        print("== Keybag")
        print("Keybag type: %s keybag (%d)" % (KEYBAG_TYPES[self.type], self.type))
        print("Keybag version: %d" % self.attrs[b"VERS"])
        print("Keybag UUID: %s" % anonymize(hexlify(self.uuid)))
                    "Public key"]))
        for k, ck in self.classKeys.items():
            if k == 6:print("")

                anonymize(hexlify(ck.get(b"KEY", b""))).ljust(65),
                anonymize(hexlify(ck.get(b"WPKY", b""))).ljust(65),

def loopTLVBlocks(blob):
    i = 0
    while i + 8 <= len(blob):
        tag = blob[i:i+4]
        length = struct.unpack(">L",blob[i+4:i+8])[0]
        data = blob[i+8:i+8+length]
        yield (tag,data)
        i += 8 + length

def unpack64bit(s):
    return struct.unpack(">Q",s)[0]
def pack64bit(s):
    return struct.pack(">Q",s)

def AESUnwrap(kek, wrapped):
    C = []
    for i in range(len(wrapped)//8):
    n = len(C) - 1
    R = [0] * (n+1)
    A = C[0]

    for i in range(1,n+1):
        R[i] = C[i]

    for j in reversed(range(0,6)):
        for i in reversed(range(1,n+1)):
            todec = pack64bit(A ^ (n*j+i))
            todec += pack64bit(R[i])
            B =
            A = unpack64bit(B[:8])
            R[i] = unpack64bit(B[8:])

    if A != 0xa6a6a6a6a6a6a6a6:
        return None
    res = b"".join(map(pack64bit, R[1:]))
    return res

ZEROIV = "\x00"*16
def AESdecryptCBC(data, key, iv=ZEROIV, padding=False):
    if len(data) % 16:
        print("AESdecryptCBC: data length not /16, truncating")
        data = data[0:(len(data)/16) * 16]
    data =, Crypto.Cipher.AES.MODE_CBC, iv).decrypt(data)
    if padding:
        return removePadding(16, data)
    return data

# here are some utility functions, one making sure I don’t leak my
# secret keys when posting the output on Stack Exchange

anon_random = random.Random(0)
memo = {}
def anonymize(s):
    if type(s) == str:
        s = s.encode('utf-8')
    global anon_random, memo
        if s in memo:
            return memo[s]
        possible_alphabets = [
            string.digits + 'abcdef',
            "".join(chr(x) for x in range(0, 256)),
        for a in possible_alphabets:
            if all((chr(c) if type(c) == int else c) in a for c in s):
                alphabet = a
        ret = "".join([anon_random.choice(alphabet) for i in range(len(s))])
        memo[s] = ret
        return ret
        return s

def wrap(s, width=78):
    "Return a width-wrapped repr(s)-like string without breaking on \’s"
    s = repr(s)
    quote = s[0]
    s = s[1:-1]
    ret = []
    while len(s):
        i = s.rfind('\\', 0, width)
        if i <= width - 4: # "\x??" is four characters
            i = width
        s = s[i:]
    return '\n'.join("%s%s%s" % (quote, line ,quote) for line in ret)

def readpipe(path):
    if stat.S_ISFIFO(os.stat(path).st_mode):
        with open(path, 'rb') as pipe:
        raise Exception("Not a pipe: {!r}".format(path))

if __name__ == '__main__':

Which then prints this output:

Warning: All output keys are FAKE to protect your privacy
== Keybag
Keybag type: Backup keybag (1)
Keybag version: 3
Keybag UUID: dc6486c479e84c94efce4bea7169ef7d
Class                                                WRAP Type       Key                                                              WPKY                                                             Public key
NSFileProtectionComplete                             2    AES                                                                         4c80b6da07d35d393fc7158e18b8d8f9979694329a71ceedee86b4cde9f97afec197ad3b13c5d12b
NSFileProtectionCompleteUnlessOpen                   2    AES                                                                         09e8a0a9965f00f213ce06143a52801f35bde2af0ad54972769845d480b5043f545fa9b66a0353a6
NSFileProtectionCompleteUntilFirstUserAuthentication 2    AES                                                                         e966b6a0742878ce747cec3fa1bf6a53b0d811ad4f1d6147cd28a5d400a8ffe0bbabea5839025cb5
NSFileProtectionNone                                 2    AES                                                                         902f46847302816561e7df57b64beea6fa11b0068779a65f4c651dbe7a1630f323682ff26ae7e577
NSFileProtectionRecovery?                            3    AES                                                                         a3935fed024cd9bc11d0300d522af8e89accfbe389d7c69dca02841df46c0a24d0067dba2f696072

kSecAttrAccessibleWhenUnlocked                       2    AES                                                                         09a1856c7e97a51a9c2ecedac8c3c7c7c10e7efa931decb64169ee61cb07a0efb115050fd1e33af1
kSecAttrAccessibleAfterFirstUnlock                   2    AES                                                                         0509d215f2f574efa2f192efc53c460201168b26a175f066b5347fc48bc76c637e27a730b904ca82
kSecAttrAccessibleAlways                             2    AES                                                                         b7ac3c4f1e04896144ce90c4583e26489a86a6cc45a2b692a5767b5a04b0907e081daba009fdbb3c
kSecAttrAccessibleWhenUnlockedThisDeviceOnly         3    AES                                                                         417526e67b82e7c6c633f9063120a299b84e57a8ffee97b34020a2caf6e751ec5750053833ab4d45
kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly     3    AES                                                                         b0e17b0cf7111c6e716cd0272de5684834798431c1b34bab8d1a1b5aba3d38a3a42c859026f81ccc
kSecAttrAccessibleAlwaysThisDeviceOnly               3    AES                                                                         9b3bdc59ae1d85703aa7f75d49bdc600bf57ba4a458b20a003a10f6e36525fb6648ba70e6602d8b2

== Passcode key

== Keybag
Keybag type: Backup keybag (1)
Keybag version: 3
Keybag UUID: dc6486c479e84c94efce4bea7169ef7d
Class                                                WRAP Type       Key                                                              WPKY                                                             Public key
NSFileProtectionComplete                             2    AES        64e8fc94a7b670b0a9c4a385ff395fe9ba5ee5b0d9f5a5c9f0202ef7fdcb386f 4c80b6da07d35d393fc7158e18b8d8f9979694329a71ceedee86b4cde9f97afec197ad3b13c5d12b
NSFileProtectionCompleteUnlessOpen                   2    AES        22a218c9c446fbf88f3ccdc2ae95f869c308faaa7b3e4fe17b78cbf2eeaf4ec9 09e8a0a9965f00f213ce06143a52801f35bde2af0ad54972769845d480b5043f545fa9b66a0353a6
NSFileProtectionCompleteUntilFirstUserAuthentication 2    AES        1004c6ca6e07d2b507809503180edf5efc4a9640227ac0d08baf5918d34b44ef e966b6a0742878ce747cec3fa1bf6a53b0d811ad4f1d6147cd28a5d400a8ffe0bbabea5839025cb5
NSFileProtectionNone                                 2    AES        2e809a0cd1a73725a788d5d1657d8fd150b0e360460cb5d105eca9c60c365152 902f46847302816561e7df57b64beea6fa11b0068779a65f4c651dbe7a1630f323682ff26ae7e577
NSFileProtectionRecovery?                            3    AES        9a078d710dcd4a1d5f70ea4062822ea3e9f7ea034233e7e290e06cf0d80c19ca a3935fed024cd9bc11d0300d522af8e89accfbe389d7c69dca02841df46c0a24d0067dba2f696072

kSecAttrAccessibleWhenUnlocked                       2    AES        606e5328816af66736a69dfe5097305cf1e0b06d6eb92569f48e5acac3f294a4 09a1856c7e97a51a9c2ecedac8c3c7c7c10e7efa931decb64169ee61cb07a0efb115050fd1e33af1
kSecAttrAccessibleAfterFirstUnlock                   2    AES        6a4b5292661bac882338d5ebb51fd6de585befb4ef5f8ffda209be8ba3af1b96 0509d215f2f574efa2f192efc53c460201168b26a175f066b5347fc48bc76c637e27a730b904ca82
kSecAttrAccessibleAlways                             2    AES        c0ed717947ce8d1de2dde893b6026e9ee1958771d7a7282dd2116f84312c2dd2 b7ac3c4f1e04896144ce90c4583e26489a86a6cc45a2b692a5767b5a04b0907e081daba009fdbb3c
kSecAttrAccessibleWhenUnlockedThisDeviceOnly         3    AES        80d8c7be8d5103d437f8519356c3eb7e562c687a5e656cfd747532f71668ff99 417526e67b82e7c6c633f9063120a299b84e57a8ffee97b34020a2caf6e751ec5750053833ab4d45
kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly     3    AES        a875a15e3ff901351c5306019e3b30ed123e6c66c949bdaa91fb4b9a69a3811e b0e17b0cf7111c6e716cd0272de5684834798431c1b34bab8d1a1b5aba3d38a3a42c859026f81ccc
kSecAttrAccessibleAlwaysThisDeviceOnly               3    AES        1e7756695d337e0b06c764734a9ef8148af20dcc7a636ccfea8b2eb96a9e9373 9b3bdc59ae1d85703aa7f75d49bdc600bf57ba4a458b20a003a10f6e36525fb6648ba70e6602d8b2

== decrypted data:
'<?xml version="1.0" encoding="UTF-8"?>\n<!DOCTYPE plist PUBLIC "-//Apple//DTD '
'PLIST 1.0//EN" "">\n<plist versi'

== pretty-printed plist
{'DCIMLastDirectoryNumber': 100, 'DCIMLastFileNumber': 3}

Extra credit

The iphone-dataprotection code posted by Bédrune and Sigwald can decrypt the keychain from a backup, including fun things like saved wifi and website passwords:

$ python iphone-dataprotection/python_scripts/ ...

|                              Passwords                                             |
|Service           |Account          |Data           |Access group  |Protection class|
|AirPort           |Ed’s Coffee Shop |<3FrenchRoast  |apple         |AfterFirstUnlock|

That code no longer works on backups from phones using the latest iOS, but there are some golang ports that have been kept up to date allowing access to the keychain.

Creating executable files in Linux

What you describe is the correct way to handle this.

You said that you want to stay in the GUI. You can usually set the execute bit through the file properties menu. You could also learn how to create a custom action for the context menu to do this for you if you're so inclined. This depends on your desktop environment of course.

If you use a more advanced editor, you can script the action to happen when the file is saved. For example (I'm only really familiar with vim), you could add this to your .vimrc to make any new file that starts with "#!/*/bin/*" executable.

au BufWritePost * if getline(1) =~ "^#!" | if getline(1) =~ "/bin/" | silent !chmod +x <afile> | endif | endif

ASP.NET Web API session or something?

in Global.asax add

public override void Init()
    this.PostAuthenticateRequest += MvcApplication_PostAuthenticateRequest;

void MvcApplication_PostAuthenticateRequest(object sender, EventArgs e)

give it a shot ;)

MVC ajax json post to controller action method

Below is how I got this working.

The Key point was: I needed to use the ViewModel associated with the view in order for the runtime to be able to resolve the object in the request.

[I know that that there is a way to bind an object other than the default ViewModel object but ended up simply populating the necessary properties for my needs as I could not get it to work]

  public ActionResult GetDataForInvoiceNumber(MyViewModel myViewModel)  
     var invoiceNumberQueryResult = _viewModelBuilder.HydrateMyViewModelGivenInvoiceDetail(myViewModel.InvoiceNumber, myViewModel.SelectedCompanyCode);
     return Json(invoiceNumberQueryResult, JsonRequestBehavior.DenyGet);

The JQuery script used to call this action method:

var requestData = {
         InvoiceNumber: $.trim(this.value),
         SelectedCompanyCode: $.trim($('#SelectedCompanyCode').val())

         url: '/en/myController/GetDataForInvoiceNumber',
         type: 'POST',
         data: JSON.stringify(requestData),
         dataType: 'json',
         contentType: 'application/json; charset=utf-8',
         error: function (xhr) {
            alert('Error: ' + xhr.statusText);
         success: function (result) {
         async: true,
         processData: false

How do I show running processes in Oracle DB?

Keep in mind that there are processes on the database which may not currently support a session.

If you're interested in all processes you'll want to look to v$process (or gv$process on RAC)

Clone Object without reference javascript

If you use an = statement to assign a value to a var with an object on the right side, javascript will not copy but reference the object.

You can use lodash's clone method

var obj = {a: 25, b: 50, c: 75};
var A = _.clone(obj);

Or lodash's cloneDeep method if your object has multiple object levels

var obj = {a: 25, b: {a: 1, b: 2}, c: 75};
var A = _.cloneDeep(obj);

Or lodash's merge method if you mean to extend the source object

var obj = {a: 25, b: {a: 1, b: 2}, c: 75};
var A = _.merge({}, obj, {newkey: "newvalue"});

Or you can use jQuerys extend method:

var obj = {a: 25, b: 50, c: 75};
var A = $.extend(true,{},obj);

Here is jQuery 1.11 extend method's source code :

jQuery.extend = jQuery.fn.extend = function() {
    var src, copyIsArray, copy, name, options, clone,
        target = arguments[0] || {},
        i = 1,
        length = arguments.length,
        deep = false;

    // Handle a deep copy situation
    if ( typeof target === "boolean" ) {
        deep = target;

        // skip the boolean and the target
        target = arguments[ i ] || {};

    // Handle case when target is a string or something (possible in deep copy)
    if ( typeof target !== "object" && !jQuery.isFunction(target) ) {
        target = {};

    // extend jQuery itself if only one argument is passed
    if ( i === length ) {
        target = this;

    for ( ; i < length; i++ ) {
        // Only deal with non-null/undefined values
        if ( (options = arguments[ i ]) != null ) {
            // Extend the base object
            for ( name in options ) {
                src = target[ name ];
                copy = options[ name ];

                // Prevent never-ending loop
                if ( target === copy ) {

                // Recurse if we're merging plain objects or arrays
                if ( deep && copy && ( jQuery.isPlainObject(copy) || (copyIsArray = jQuery.isArray(copy)) ) ) {
                    if ( copyIsArray ) {
                        copyIsArray = false;
                        clone = src && jQuery.isArray(src) ? src : [];

                    } else {
                        clone = src && jQuery.isPlainObject(src) ? src : {};

                    // Never move original objects, clone them
                    target[ name ] = jQuery.extend( deep, clone, copy );

                // Don't bring in undefined values
                } else if ( copy !== undefined ) {
                    target[ name ] = copy;

    // Return the modified object
    return target;

How do I write a bash script to restart a process if it dies?

Avoid PID-files, crons, or anything else that tries to evaluate processes that aren't their children.

There is a very good reason why in UNIX, you can ONLY wait on your children. Any method (ps parsing, pgrep, storing a PID, ...) that tries to work around that is flawed and has gaping holes in it. Just say no.

Instead you need the process that monitors your process to be the process' parent. What does this mean? It means only the process that starts your process can reliably wait for it to end. In bash, this is absolutely trivial.

until myserver; do
    echo "Server 'myserver' crashed with exit code $?.  Respawning.." >&2
    sleep 1

The above piece of bash code runs myserver in an until loop. The first line starts myserver and waits for it to end. When it ends, until checks its exit status. If the exit status is 0, it means it ended gracefully (which means you asked it to shut down somehow, and it did so successfully). In that case we don't want to restart it (we just asked it to shut down!). If the exit status is not 0, until will run the loop body, which emits an error message on STDERR and restarts the loop (back to line 1) after 1 second.

Why do we wait a second? Because if something's wrong with the startup sequence of myserver and it crashes immediately, you'll have a very intensive loop of constant restarting and crashing on your hands. The sleep 1 takes away the strain from that.

Now all you need to do is start this bash script (asynchronously, probably), and it will monitor myserver and restart it as necessary. If you want to start the monitor on boot (making the server "survive" reboots), you can schedule it in your user's cron(1) with an @reboot rule. Open your cron rules with crontab:

crontab -e

Then add a rule to start your monitor script:

@reboot /usr/local/bin/myservermonitor

Alternatively; look at inittab(5) and /etc/inittab. You can add a line in there to have myserver start at a certain init level and be respawned automatically.


Let me add some information on why not to use PID files. While they are very popular; they are also very flawed and there's no reason why you wouldn't just do it the correct way.

Consider this:

  1. PID recycling (killing the wrong process):

    • /etc/init.d/foo start: start foo, write foo's PID to /var/run/
    • A while later: foo dies somehow.
    • A while later: any random process that starts (call it bar) takes a random PID, imagine it taking foo's old PID.
    • You notice foo's gone: /etc/init.d/foo/restart reads /var/run/, checks to see if it's still alive, finds bar, thinks it's foo, kills it, starts a new foo.
  2. PID files go stale. You need over-complicated (or should I say, non-trivial) logic to check whether the PID file is stale, and any such logic is again vulnerable to 1..

  3. What if you don't even have write access or are in a read-only environment?

  4. It's pointless overcomplication; see how simple my example above is. No need to complicate that, at all.

See also: Are PID-files still flawed when doing it 'right'?

By the way; even worse than PID files is parsing ps! Don't ever do this.

  1. ps is very unportable. While you find it on almost every UNIX system; its arguments vary greatly if you want non-standard output. And standard output is ONLY for human consumption, not for scripted parsing!
  2. Parsing ps leads to a LOT of false positives. Take the ps aux | grep PID example, and now imagine someone starting a process with a number somewhere as argument that happens to be the same as the PID you stared your daemon with! Imagine two people starting an X session and you grepping for X to kill yours. It's just all kinds of bad.

If you don't want to manage the process yourself; there are some perfectly good systems out there that will act as monitor for your processes. Look into runit, for example.

Debugging the error "gcc: error: x86_64-linux-gnu-gcc: No such file or directory"

After a fair amount of work, I was able to get it to build on Ubuntu 12.04 x86 and Debian 7.4 x86_64. I wrote up a guide below. Can you please try following it to see if it resolves the issue?

If not please let me know where you get stuck.

Install Common Dependencies

sudo apt-get install build-essential autoconf libtool pkg-config python-opengl python-imaging python-pyrex python-pyside.qtopengl idle-python2.7 qt4-dev-tools qt4-designer libqtgui4 libqtcore4 libqt4-xml libqt4-test libqt4-script libqt4-network libqt4-dbus python-qt4 python-qt4-gl libgle3 python-dev

Install NumArray 1.5.2

wget -O numarray-1.5.2.tgz
tar xfvz numarray-1.5.2.tgz
cd numarray-1.5.2
sudo python install

Install Numeric 23.8

wget -O numeric-23.8.tgz
tar xfvz numeric-23.8.tgz
cd Numeric-23.8
sudo python install

Install HDF5 1.6.5

tar xfvz hdf5-1.6.5.tar.gz
cd hdf5-1.6.5
./configure --prefix=/usr/local
sudo make 
sudo make install

Install Nanoengineer

git clone
cd nanoengineer
sudo make install


On Debian Jessie, you will receive the error message that cant pants mentioned. There seems to be an issue in the automake scripts. x86_64-linux-gnu-gcc is inserted in CFLAGS and gcc will interpret that as a name of one of the source files. As a workaround, let's create an empty file with that name. Empty so that it won't change the program and that very name so that compiler picks it up. From the cloned nanoengineer directory, run this command to make gcc happy (it is a hack yes, but it does work) ...

touch sim/src/x86_64-linux-gnu-gcc

If you receive an error message when attemping to compile HDF5 along the lines of: "error: call to ‘__open_missing_mode’ declared with attribute error: open with O_CREAT in second argument needs 3 arguments", then modify the file perform/zip_perf.c, line 548 to look like the following and then rerun make...

output = open(filename, O_RDWR | O_CREAT, S_IRUSR|S_IWUSR);

If you receive an error message about Numeric/arrayobject.h not being found when building Nanoengineer, try running

export CPPFLAGS=-I/usr/local/include/python2.7
sudo make install

If you receive an error message similar to "TRACE_PREFIX undeclared", modify the file sim/src/simhelp.c lines 38 to 41 to look like this and re-run make:

static char tracePrefix[] = "";
static char tracePrefix[] = "";

If you receive an error message when trying to launch NanoEngineer-1 that mentions something similar to "cannot import name GL_ARRAY_BUFFER_ARB", modify the lines in the following files


that look like this:


to look like this:

from OpenGL.GL.ARB.vertex_buffer_object import GL_ARRAY_BUFFER_AR
from OpenGL.GL.ARB.vertex_buffer_object import GL_ELEMENT_ARRAY_BUFFER_ARB

I also found an additional troubleshooting text file that has been removed, but you can find it here

How to make phpstorm display line numbers by default?

Settings -> editor | appearance | Show line numbers

ASP.NET email validator regex

For regex, I first look at this web site:

What is a Java String's default initial value?

Any object if it is initailised , its defeault value is null, until unless we explicitly provide a default value.

Error: Execution failed for task ':app:clean'. Unable to delete file

Clean project from Terminal using this command gradlew clean.

enter image description here

How to remove the last character from a bash grep output

you can strip the beginnings and ends of a string by N characters using this bash construct, as someone said already

$ fred=abcdefg.rpm
$ echo ${fred:1:-4}

HOWEVER, this is not supported in older versions of bash.. as I discovered just now writing a script for a Red hat EL6 install process. This is the sole reason for posting here. A hacky way to achieve this is to use sed with extended regex like this:

$ fred=abcdefg.rpm
$ echo $fred | sed -re 's/^.(.*)....$/\1/g'

JavaScript: Collision detection

This is a simple way that is inefficient, but it's quite reasonable when you don't need anything too complex or you don't have many objects.

Otherwise there are many different algorithms, but most of them are quite complex to implement.

For example, you can use a divide et impera approach in which you cluster objects hierarchically according to their distance and you give to every cluster a bounding box that contains all the items of the cluster. Then you can check which clusters collide and avoid checking pairs of object that belong to clusters that are not colliding/overlapped.

Otherwise, you can figure out a generic space partitioning algorithm to split up in a similar way the objects to avoid useless checks. These kind of algorithms split the collision detection in two phases: a coarse one in which you see what objects maybe colliding and a fine one in which you effectively check single objects. For example, you can use a QuadTree (Wikipedia) to work out an easy solution...

Take a look at the Wikipedia page. It can give you some hints.

How to use regex in file find

Use -regex not -name, and be aware that the regex matches against what find would print, e.g. "/home/test/test.log" not "test.log"

Insert current date/time using now() in a field using MySQL/PHP

Currently, and with the new versions of Mysql can insert the current date automatically without adding a code in your PHP file. You can achieve that from Mysql while setting up your database as follows:

enter image description here

Now, any new post will automatically get a unique date and time. Hope this can help.

Maximum number of rows of CSV data in excel sheet

In my memory, excel (versions >= 2007) limits the power 2 of 20: 1.048.576 lines.

Csv is over to this boundary, like ordinary text file. So you will be care of the transfer between two formats.

Change primary key column in SQL Server

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



with these:



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

 WHERE TABLE_NAME = 'history'

Bootstrap table striped: How do I change the stripe background colour?

If using SASS and Bootstrap 4, you can change the alternating background row color for both .table and .table-dark with:

$table-accent-bg: #990000;
$table-dark-accent-bg: #990000;

Where and why do I have to put the "template" and "typename" keywords?



While the rules in C++03 about when you need typename and template are largely reasonable, there is one annoying disadvantage of its formulation

template<typename T>
struct A {
  typedef int result_type;

  void f() {
    // error, "this" is dependent, "template" keyword needed

    // OK

    // error, "A<T>" is dependent, "typename" keyword needed
    A<T>::result_type n1;

    // OK
    result_type n2; 

  template<typename U>
  void g();

As can be seen, we need the disambiguation keyword even if the compiler could perfectly figure out itself that A::result_type can only be int (and is hence a type), and this->g can only be the member template g declared later (even if A is explicitly specialized somewhere, that would not affect the code within that template, so its meaning cannot be affected by a later specialization of A!).

Current instantiation

To improve the situation, in C++11 the language tracks when a type refers to the enclosing template. To know that, the type must have been formed by using a certain form of name, which is its own name (in the above, A, A<T>, ::A<T>). A type referenced by such a name is known to be the current instantiation. There may be multiple types that are all the current instantiation if the type from which the name is formed is a member/nested class (then, A::NestedClass and A are both current instantiations).

Based on this notion, the language says that CurrentInstantiation::Foo, Foo and CurrentInstantiationTyped->Foo (such as A *a = this; a->Foo) are all member of the current instantiation if they are found to be members of a class that is the current instantiation or one of its non-dependent base classes (by just doing the name lookup immediately).

The keywords typename and template are now not required anymore if the qualifier is a member of the current instantiation. A keypoint here to remember is that A<T> is still a type-dependent name (after all T is also type dependent). But A<T>::result_type is known to be a type - the compiler will "magically" look into this kind of dependent types to figure this out.

struct B {
  typedef int result_type;

template<typename T>
struct C { }; // could be specialized!

template<typename T>
struct D : B, C<T> {
  void f() {
    // OK, member of current instantiation!
    // A::result_type is not dependent: int
    D::result_type r1;

    // error, not a member of the current instantiation
    D::questionable_type r2;

    // OK for now - relying on C<T> to provide it
    // But not a member of the current instantiation
    typename D::questionable_type r3;        

That's impressive, but can we do better? The language even goes further and requires that an implementation again looks up D::result_type when instantiating D::f (even if it found its meaning already at definition time). When now the lookup result differs or results in ambiguity, the program is ill-formed and a diagnostic must be given. Imagine what happens if we defined C like this

struct C<int> {
  typedef bool result_type;
  typedef int questionable_type;

A compiler is required to catch the error when instantiating D<int>::f. So you get the best of the two worlds: "Delayed" lookup protecting you if you could get in trouble with dependent base classes, and also "Immediate" lookup that frees you from typename and template.

Unknown specializations

In the code of D, the name typename D::questionable_type is not a member of the current instantiation. Instead the language marks it as a member of an unknown specialization. In particular, this is always the case when you are doing DependentTypeName::Foo or DependentTypedName->Foo and either the dependent type is not the current instantiation (in which case the compiler can give up and say "we will look later what Foo is) or it is the current instantiation and the name was not found in it or its non-dependent base classes and there are also dependent base classes.

Imagine what happens if we had a member function h within the above defined A class template

void h() {
  typename A<T>::questionable_type x;

In C++03, the language allowed to catch this error because there could never be a valid way to instantiate A<T>::h (whatever argument you give to T). In C++11, the language now has a further check to give more reason for compilers to implement this rule. Since A has no dependent base classes, and A declares no member questionable_type, the name A<T>::questionable_type is neither a member of the current instantiation nor a member of an unknown specialization. In that case, there should be no way that that code could validly compile at instantiation time, so the language forbids a name where the qualifier is the current instantiation to be neither a member of an unknown specialization nor a member of the current instantiation (however, this violation is still not required to be diagnosed).

Examples and trivia

You can try this knowledge on this answer and see whether the above definitions make sense for you on a real-world example (they are repeated slightly less detailed in that answer).

The C++11 rules make the following valid C++03 code ill-formed (which was not intended by the C++ committee, but will probably not be fixed)

struct B { void f(); };
struct A : virtual B { void f(); };

template<typename T>
struct C : virtual B, T {
  void g() { this->f(); }

int main() { 
  C<A> c; c.g(); 

This valid C++03 code would bind this->f to A::f at instantiation time and everything is fine. C++11 however immediately binds it to B::f and requires a double-check when instantiating, checking whether the lookup still matches. However when instantiating C<A>::g, the Dominance Rule applies and lookup will find A::f instead.

How to compare types

If your instance is a Type:

Type typeFiled;
if (typeField == typeof(string))

but if your instance is an object and not a Type use the as operator:

object value;
string text = value as string;
if (text != null)
    // value is a string and you can do your work here

this has the advantage to convert value only once into the specified type.

Modifying a subset of rows in a pandas dataframe

Starting from pandas 0.20 ix is deprecated. The right way is to use df.loc

here is a working example

>>> import pandas as pd 
>>> import numpy as np 
>>> df = pd.DataFrame({"A":[0,1,0], "B":[2,0,5]}, columns=list('AB'))
>>> df.loc[df.A == 0, 'B'] = np.nan
>>> df
   A   B
0  0 NaN
1  1   0
2  0 NaN


As explained in the doc here, .loc is primarily label based, but may also be used with a boolean array.

So, what we are doing above is applying df.loc[row_index, column_index] by:

  • Exploiting the fact that loc can take a boolean array as a mask that tells pandas which subset of rows we want to change in row_index
  • Exploiting the fact loc is also label based to select the column using the label 'B' in the column_index

We can use logical, condition or any operation that returns a series of booleans to construct the array of booleans. In the above example, we want any rows that contain a 0, for that we can use df.A == 0, as you can see in the example below, this returns a series of booleans.

>>> df = pd.DataFrame({"A":[0,1,0], "B":[2,0,5]}, columns=list('AB'))
>>> df 
   A  B
0  0  2
1  1  0
2  0  5
>>> df.A == 0 
0     True
1    False
2     True
Name: A, dtype: bool

Then, we use the above array of booleans to select and modify the necessary rows:

>>> df.loc[df.A == 0, 'B'] = np.nan
>>> df
   A   B
0  0 NaN
1  1   0
2  0 NaN

For more information check the advanced indexing documentation here.

Tensorflow set CUDA_VISIBLE_DEVICES within jupyter

You can set environment variables in the notebook using os.environ. Do the following before initializing TensorFlow to limit TensorFlow to first GPU.

import os
os.environ["CUDA_DEVICE_ORDER"]="PCI_BUS_ID"   # see issue #152

You can double check that you have the correct devices visible to TF

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

I tend to use it from utility module like notebook_util

import notebook_util
import tensorflow as tf

SQL Server 2008 Row Insert and Update timestamps


CREATE TABLE [dbo].[Names]
    [Name] [nvarchar](64) NOT NULL,
    [UpdateTS] [smalldatetime] NOT NULL


PS I think a smalldatetime is good enough. You may decide differently.

Can you not do this at the "moment of impact" ?

In Sql Server, this is common:

Update dbo.MyTable 

ColA = @SomeValue , 

Sql Server has a "timestamp" datatype.

But it may not be what you think.

Here is a reference:

Here is a little RowVersion (synonym for timestamp) example:

CREATE TABLE [dbo].[Names]
    [Name] [nvarchar](64) NOT NULL,
    RowVers rowversion ,
    [UpdateTS] [datetime] NOT NULL


INSERT INTO dbo.Names (Name,UpdateTS)

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

Update dbo.Names Set Name = Name

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

Maybe a complete working example:

DROP TABLE [dbo].[Names]

CREATE TABLE [dbo].[Names]
    [Name] [nvarchar](64) NOT NULL,
    RowVers rowversion ,
    [UpdateTS] [datetime] NOT NULL



CREATE TRIGGER dbo.trgKeepUpdateDateInSync_ByeByeBye ON dbo.Names


Update dbo.Names Set UpdateTS = CURRENT_TIMESTAMP from dbo.Names myAlias , inserted triggerInsertedTable where 
triggerInsertedTable.Name = myAlias.Name



INSERT INTO dbo.Names (Name,UpdateTS)

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

Update dbo.Names Set Name = Name , UpdateTS = '03/03/2003' /* notice that even though I set it to 2003, the trigger takes over */

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

Matching on the "Name" value is probably not wise.

Try this more mainstream example with a SurrogateKey

DROP TABLE [dbo].[Names]

CREATE TABLE [dbo].[Names]
    SurrogateKey int not null Primary Key Identity (1001,1),
    [Name] [nvarchar](64) NOT NULL,
    RowVers rowversion ,
    [UpdateTS] [datetime] NOT NULL



CREATE TRIGGER dbo.trgKeepUpdateDateInSync_ByeByeBye ON dbo.Names


   UPDATE dbo.Names
    From  dbo.Names myAlias
    WHERE exists ( select null from inserted triggerInsertedTable where myAlias.SurrogateKey = triggerInsertedTable.SurrogateKey)



INSERT INTO dbo.Names (Name,UpdateTS)

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

Update dbo.Names Set Name = Name , UpdateTS = '03/03/2003' /* notice that even though I set it to 2003, the trigger takes over */

select *  ,  ConvertedRowVers = CONVERT(bigint,RowVers) from [dbo].[Names]

how to convert a string date to date format in oracle10g

You can convert a string to a DATE using the TO_DATE function, then reformat the date as another string using TO_CHAR, i.e.:

         TO_DATE('15/August/2009,4:30 PM'
                ,'DD/Month/YYYY,HH:MI AM')


For example, if your table name is MYTABLE and the varchar2 column is MYDATESTRING:

                ,'DD/Month/YYYY,HH:MI AM')

I don't understand -Wl,-rpath -Wl,

One other thing. You may need to specify the -L option as well - eg

-Wl,-rpath,/path/to/foo -L/path/to/foo -lbaz

or you may end up with an error like

ld: cannot find -lbaz

Adding git branch on the Bash command prompt

parse_git_branch() {
    git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/ (\1)/'
export PS1='\[\e]0;\w\a\]\n\[\e[32m\]\u@\h \[\e[33m\]\w\[\e[0m\]$(parse_git_branch)\n\$ '

overlay two images in android to set an imageview

this is my solution:

    public Bitmap Blend(Bitmap topImage1, Bitmap bottomImage1, PorterDuff.Mode Type) {

        Bitmap workingBitmap = Bitmap.createBitmap(topImage1);
        Bitmap topImage = workingBitmap.copy(Bitmap.Config.ARGB_8888, true);

        Bitmap workingBitmap2 = Bitmap.createBitmap(bottomImage1);
        Bitmap bottomImage = workingBitmap2.copy(Bitmap.Config.ARGB_8888, true);

        Rect dest = new Rect(0, 0, bottomImage.getWidth(), bottomImage.getHeight());
        new BitmapFactory.Options().inPreferredConfig = Bitmap.Config.ARGB_8888;
        Canvas canvas = new Canvas(bottomImage);
        Paint paint = new Paint();

        paint.setXfermode(new PorterDuffXfermode(Type));

        canvas.drawBitmap(topImage, null, dest, paint);
        return bottomImage;

usage :

imageView.setImageBitmap(Blend(topBitmap, bottomBitmap, PorterDuff.Mode.SCREEN));


imageView.setImageBitmap(Blend(topBitmap, bottomBitmap, PorterDuff.Mode.OVERLAY));

and the results :

Overlay mode : Overlay mode

Screen mode: Screen mode

Which version of Python do I have installed?

If you have Python installed then the easiest way you can check the version number is by typing "python" in your command prompt. It will show you the version number and if it is running on 32 bit or 64 bit and some other information. For some applications you would want to have a latest version and sometimes not. It depends on what packages you want to install or use.

Select multiple columns using Entity Framework

Why don't you create a new object right in the .Select:

.Select(x => new PInfo{ 
    ServerName = x.ServerName, 
    ProcessID = x.ProcessID, 
    UserName = x.Username }).ToList();

How to solve this java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream?

You will have to download file from here and select

Now, Next add this downloaded files into your project:

Right click to your project ->Build path->Configure BuidPath ->

Insert a line at specific line number with sed or awk

sed -e '8iProject_Name=sowstest' -i start using GNU sed

Sample run:

[root@node23 ~]# for ((i=1; i<=10; i++)); do echo "Line #$i"; done > a_file
[root@node23 ~]# cat a_file
Line #1
Line #2
Line #3
Line #4
Line #5
Line #6
Line #7
Line #8
Line #9
Line #10
[root@node23 ~]# sed -e '3ixxx inserted line xxx' -i a_file 
[root@node23 ~]# cat -An a_file 
     1  Line #1$
     2  Line #2$
     3  xxx inserted line xxx$
     4  Line #3$
     5  Line #4$
     6  Line #5$
     7  Line #6$
     8  Line #7$
     9  Line #8$
    10  Line #9$
    11  Line #10$
[root@node23 ~]# 
[root@node23 ~]# sed -e '5ixxx (inserted) "line" xxx' -i a_file
[root@node23 ~]# cat -n a_file 
     1  Line #1
     2  Line #2
     3  xxx inserted line xxx
     4  Line #3
     5  xxx (inserted) "line" xxx
     6  Line #4
     7  Line #5
     8  Line #6
     9  Line #7
    10  Line #8
    11  Line #9
    12  Line #10
[root@node23 ~]# 

Swift Modal View Controller with transparent background

You can do it like this:

In your main view controller:

func showModal() {
    let modalViewController = ModalViewController()
    modalViewController.modalPresentationStyle = .overCurrentContext
    presentViewController(modalViewController, animated: true, completion: nil)

In your modal view controller:

class ModalViewController: UIViewController {
    override func viewDidLoad() {
        view.backgroundColor = UIColor.clearColor()
        view.opaque = false

If you are working with a storyboard:

Just add a Storyboard Segue with Kind set to Present Modally to your modal view controller and on this view controller set the following values:

  • Background = Clear Color
  • Drawing = Uncheck the Opaque checkbox
  • Presentation = Over Current Context

As Crashalot pointed out in his comment: Make sure the segue only uses Default for both Presentation and Transition. Using Current Context for Presentation makes the modal turn black instead of remaining transparent.

Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?

You can use the logical 'OR' operator in place of the Elvis operator:

For example displayname = || "Anonymous" .

But Javascript currently doesn't have the other functionality. I'd recommend looking at CoffeeScript if you want an alternative syntax. It has some shorthand that is similar to what you are looking for.

For example The Existential Operator

zip = lottery.drawWinner?().address?.zipcode

Function shortcuts

()->  // equivalent to function(){}

Sexy function calling

func 'arg1','arg2' // equivalent to func('arg1','arg2')

There is also multiline comments and classes. Obviously you have to compile this to javascript or insert into the page as <script type='text/coffeescript>' but it adds a lot of functionality :) . Using <script type='text/coffeescript'> is really only intended for development and not production.

Export a graph to .eps file with R

Yes, open a postscript() device with a filename ending in .eps, do your plot(s) and call

Pass an array of integers to ASP.NET Web API?

You just need to add [FromUri] before parameter, looks like:

GetCategories([FromUri] int[] categoryIds)

And send request: