Programs & Examples On #Radians

Questions regarding angular sizes, arguments for trigonometric functions geometry etc.

Creating lowpass filter in SciPy - understanding methods and units

A few comments:

  • The Nyquist frequency is half the sampling rate.
  • You are working with regularly sampled data, so you want a digital filter, not an analog filter. This means you should not use analog=True in the call to butter, and you should use scipy.signal.freqz (not freqs) to generate the frequency response.
  • One goal of those short utility functions is to allow you to leave all your frequencies expressed in Hz. You shouldn't have to convert to rad/sec. As long as you express your frequencies with consistent units, the scaling in the utility functions takes care of the normalization for you.

Here's my modified version of your script, followed by the plot that it generates.

import numpy as np
from scipy.signal import butter, lfilter, freqz
import matplotlib.pyplot as plt

def butter_lowpass(cutoff, fs, order=5):
    nyq = 0.5 * fs
    normal_cutoff = cutoff / nyq
    b, a = butter(order, normal_cutoff, btype='low', analog=False)
    return b, a

def butter_lowpass_filter(data, cutoff, fs, order=5):
    b, a = butter_lowpass(cutoff, fs, order=order)
    y = lfilter(b, a, data)
    return y

# Filter requirements.
order = 6
fs = 30.0       # sample rate, Hz
cutoff = 3.667  # desired cutoff frequency of the filter, Hz

# Get the filter coefficients so we can check its frequency response.
b, a = butter_lowpass(cutoff, fs, order)

# Plot the frequency response.
w, h = freqz(b, a, worN=8000)
plt.subplot(2, 1, 1)
plt.plot(0.5*fs*w/np.pi, np.abs(h), 'b')
plt.plot(cutoff, 0.5*np.sqrt(2), 'ko')
plt.axvline(cutoff, color='k')
plt.xlim(0, 0.5*fs)
plt.title("Lowpass Filter Frequency Response")
plt.xlabel('Frequency [Hz]')

# Demonstrate the use of the filter.
# First make some data to be filtered.
T = 5.0         # seconds
n = int(T * fs) # total number of samples
t = np.linspace(0, T, n, endpoint=False)
# "Noisy" data.  We want to recover the 1.2 Hz signal from this.
data = np.sin(1.2*2*np.pi*t) + 1.5*np.cos(9*2*np.pi*t) + 0.5*np.sin(12.0*2*np.pi*t)

# Filter the data, and plot both the original and filtered signals.
y = butter_lowpass_filter(data, cutoff, fs, order)

plt.subplot(2, 1, 2)
plt.plot(t, data, 'b-', label='data')
plt.plot(t, y, 'g-', linewidth=2, label='filtered data')
plt.xlabel('Time [sec]')


lowpass example

Using PI in python 2.7

To have access to stuff provided by math module, like pi. You need to import the module first:

import math
print (math.pi)

How can I convert radians to degrees with Python?

Python includes two functions in the math package; radians converts degrees to radians, and degrees converts radians to degrees.

To match the output of your calculator you need:

>>> math.cos(math.radians(1))

Note that all of the trig functions convert between an angle and the ratio of two sides of a triangle. cos, sin, and tan take an angle in radians as input and return the ratio; acos, asin, and atan take a ratio as input and return an angle in radians. You only convert the angles, never the ratios.

How can I get sin, cos, and tan to use degrees instead of radians?

Multiply the input by Math.PI/180 to convert from degrees to radians before calling the system trig functions.

You could also define your own functions:

function sinDegrees(angleDegrees) {
    return Math.sin(angleDegrees*Math.PI/180);

and so on.

How to calculate distance between two locations using their longitude and latitude value

Here getting distance in miles (mi)

private double distance(double lat1, double lon1, double lat2, double lon2) {
    double theta = lon1 - lon2;
    double dist = Math.sin(deg2rad(lat1)) 
                    * Math.sin(deg2rad(lat2))
                    + Math.cos(deg2rad(lat1))
                    * Math.cos(deg2rad(lat2))
                    * Math.cos(deg2rad(theta));
    dist = Math.acos(dist);
    dist = rad2deg(dist);
    dist = dist * 60 * 1.1515;
    return (dist);

private double deg2rad(double deg) {
    return (deg * Math.PI / 180.0);

private double rad2deg(double rad) {
    return (rad * 180.0 / Math.PI);

Calculate the center point of multiple latitude/longitude coordinate pairs

Dart/Flutter Calculate the center point of multiple latitude/longitude coordinate pairs

Map<String, double> getLatLngCenter(List<List<double>> coords) {
    const LATIDX = 0;
    const LNGIDX = 1;
    double sumX = 0;
    double sumY = 0;
    double sumZ = 0;

    for (var i = 0; i < coords.length; i++) {
      var lat = VectorMath.radians(coords[i][LATIDX]);
      var lng = VectorMath.radians(coords[i][LNGIDX]);
      // sum of cartesian coordinates
      sumX += Math.cos(lat) * Math.cos(lng);
      sumY += Math.cos(lat) * Math.sin(lng);
      sumZ += Math.sin(lat);

    var avgX = sumX / coords.length;
    var avgY = sumY / coords.length;
    var avgZ = sumZ / coords.length;

    // convert average x, y, z coordinate to latitude and longtitude
    var lng = Math.atan2(avgY, avgX);
    var hyp = Math.sqrt(avgX * avgX + avgY * avgY);
    var lat = Math.atan2(avgZ, hyp);

    return {
      "latitude": VectorMath.degrees(lat),
      "longitude": VectorMath.degrees(lng)

Calculating Distance between two Latitude and Longitude GeoCoordinates

Try this:

    public double getDistance(GeoCoordinate p1, GeoCoordinate p2)
        double d = p1.Latitude * 0.017453292519943295;
        double num3 = p1.Longitude * 0.017453292519943295;
        double num4 = p2.Latitude * 0.017453292519943295;
        double num5 = p2.Longitude * 0.017453292519943295;
        double num6 = num5 - num3;
        double num7 = num4 - d;
        double num8 = Math.Pow(Math.Sin(num7 / 2.0), 2.0) + ((Math.Cos(d) * Math.Cos(num4)) * Math.Pow(Math.Sin(num6 / 2.0), 2.0));
        double num9 = 2.0 * Math.Atan2(Math.Sqrt(num8), Math.Sqrt(1.0 - num8));
        return (6376500.0 * num9);

Haversine Formula in Python (Bearing and Distance between two GPS points)

There is also a vectorized implementation, which allows to use 4 numpy arrays instead of scalar values for coordinates:

def distance(s_lat, s_lng, e_lat, e_lng):

   # approximate radius of earth in km
   R = 6373.0

   s_lat = s_lat*np.pi/180.0                      
   s_lng = np.deg2rad(s_lng)     
   e_lat = np.deg2rad(e_lat)                       
   e_lng = np.deg2rad(e_lng)  

   d = np.sin((e_lat - s_lat)/2)**2 + np.cos(s_lat)*np.cos(e_lat) * np.sin((e_lng - s_lng)/2)**2

   return 2 * R * np.arcsin(np.sqrt(d))

Calculating distance between two points, using latitude longitude?

Here's a Java function that calculates the distance between two lat/long points, posted below, just in case it disappears again.

    private double distance(double lat1, double lon1, double lat2, double lon2, char unit) {
      double theta = lon1 - lon2;
      double dist = Math.sin(deg2rad(lat1)) * Math.sin(deg2rad(lat2)) + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) * Math.cos(deg2rad(theta));
      dist = Math.acos(dist);
      dist = rad2deg(dist);
      dist = dist * 60 * 1.1515;
      if (unit == 'K') {
        dist = dist * 1.609344;
      } else if (unit == 'N') {
        dist = dist * 0.8684;
      return (dist);
    /*::  This function converts decimal degrees to radians             :*/
    private double deg2rad(double deg) {
      return (deg * Math.PI / 180.0);
    /*::  This function converts radians to decimal degrees             :*/
    private double rad2deg(double rad) {
      return (rad * 180.0 / Math.PI);
    System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, 'M') + " Miles\n");
    System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, 'K') + " Kilometers\n");
    System.out.println(distance(32.9697, -96.80322, 29.46786, -98.53506, 'N') + " Nautical Miles\n");

SQL Server AS statement aliased column within WHERE statement

Logical Processing Order of the SELECT statement

The following steps show the logical processing order, or binding order, for a SELECT statement. This order determines when the objects defined in one step are made available to the clauses in subsequent steps. For example, if the query processor can bind to (access) the tables or views defined in the FROM clause, these objects and their columns are made available to all subsequent steps. Conversely, because the SELECT clause is step 8, any column aliases or derived columns defined in that clause cannot be referenced by preceding clauses. However, they can be referenced by subsequent clauses such as the ORDER BY clause. Note that the actual physical execution of the statement is determined by the query processor and the order may vary from this list.

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


Rotating a point about another point (2D)

The coordinate system on the screen is left-handed, i.e. the x coordinate increases from left to right and the y coordinate increases from top to bottom. The origin, O(0, 0) is at the upper left corner of the screen.

enter image description here

A clockwise rotation around the origin of a point with coordinates (x, y) is given by the following equations:

enter image description here

where (x', y') are the coordinates of the point after rotation and angle theta, the angle of rotation (needs to be in radians, i.e. multiplied by: PI / 180).

To perform rotation around a point different from the origin O(0,0), let's say point A(a, b) (pivot point). Firstly we translate the point to be rotated, i.e. (x, y) back to the origin, by subtracting the coordinates of the pivot point, (x - a, y - b). Then we perform the rotation and get the new coordinates (x', y') and finally we translate the point back, by adding the coordinates of the pivot point to the new coordinates (x' + a, y' + b).

Following the above description:

a 2D clockwise theta degrees rotation of point (x, y) around point (a, b) is:

Using your function prototype: (x, y) -> (p.x, p.y); (a, b) -> (cx, cy); theta -> angle:

POINT rotate_point(float cx, float cy, float angle, POINT p){

     return POINT(cos(angle) * (p.x - cx) - sin(angle) * (p.y - cy) + cx,
                  sin(angle) * (p.x - cx) + cos(angle) * (p.y - cy) + cy);

How to Rotate a UIImage 90 degrees?

A thread safe rotation function is the following (it works much better):

-(UIImage*)imageByRotatingImage:(UIImage*)initImage fromImageOrientation:(UIImageOrientation)orientation
CGImageRef imgRef = initImage.CGImage;

CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);

CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = orientation;
switch(orient) {

    case UIImageOrientationUp: //EXIF = 1
        return initImage;

    case UIImageOrientationUpMirrored: //EXIF = 2
        transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);

    case UIImageOrientationDown: //EXIF = 3
        transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
        transform = CGAffineTransformRotate(transform, M_PI);

    case UIImageOrientationDownMirrored: //EXIF = 4
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
        transform = CGAffineTransformScale(transform, 1.0, -1.0);

    case UIImageOrientationLeftMirrored: //EXIF = 5
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);

    case UIImageOrientationLeft: //EXIF = 6
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);

    case UIImageOrientationRightMirrored: //EXIF = 7
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeScale(-1.0, 1.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);

    case UIImageOrientationRight: //EXIF = 8
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);

        [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

// Create the bitmap context
CGContextRef    context = NULL;
void *          bitmapData;
int             bitmapByteCount;
int             bitmapBytesPerRow;

// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow   = (bounds.size.width * 4);
bitmapByteCount     = (bitmapBytesPerRow * bounds.size.height);
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
    return nil;

// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
CGColorSpaceRef colorspace = CGImageGetColorSpace(imgRef);
context = CGBitmapContextCreate (bitmapData,bounds.size.width,bounds.size.height,8,bitmapBytesPerRow,
                                 colorspace, kCGBitmapAlphaInfoMask & kCGImageAlphaPremultipliedLast);

if (context == NULL)
    // error creating context
    return nil;

CGContextScaleCTM(context, -1.0, -1.0);
CGContextTranslateCTM(context, -bounds.size.width, -bounds.size.height);

CGContextConcatCTM(context, transform);

// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.
CGContextDrawImage(context, CGRectMake(0,0,width, height), imgRef);

CGImageRef imgRef2 = CGBitmapContextCreateImage(context);
UIImage * image = [UIImage imageWithCGImage:imgRef2 scale:initImage.scale orientation:UIImageOrientationUp];
return image;

Fastest Way to Find Distance Between Two Lat/Long Points

if you are using MySQL 5.7.*, then you can use st_distance_sphere(POINT, POINT).

Select st_distance_sphere(POINT(-2.997065, 53.404146 ), POINT(58.615349, 23.56676 ))/1000  as distcance

What is the method for converting radians to degrees?

360 degrees = 2*pi radians

That means deg2rad(x) = x*pi/180 and rad2deg(x) = 180x/pi;

Trigger change event of dropdown

Try this:

$(document).ready(function(event) {
         // put code here

Define the change event, and trigger it immediately. This ensures the event handler is defined before calling it.

Might be late to answer the original poster, but someone else might benefit from the shorthand notation, and this follows jQuery's chaining, etc

jquery chaining

Change image size via parent div

Apply 100% width and height to your image:

<div style="height:42px;width:42px">
  <img src="http://someimage.jpg" style="width:100%; height:100%">

This way it will same size of its parent.

Compiler error: "class, interface, or enum expected"

Every method should be within a class. Your method derivativeQuiz is outside a class.

public class ClassName {

 ///your methods

How can I get the SQL of a PreparedStatement?

I'm using Java 8, JDBC driver with MySQL connector v. 5.1.31.

I may get real SQL string using this method:

// 1. make connection somehow, it's conn variable
// 2. make prepered statement template
PreparedStatement stmt = conn.prepareStatement(
    "INSERT INTO oc_manufacturer" +
    " SET" +
    " manufacturer_id = ?," +
    " name = ?," +
    " sort_order=0;"
// 3. fill template
stmt.setInt(1, 23);
stmt.setString(2, 'Google');
// 4. print sql string

So it returns smth like this:

INSERT INTO oc_manufacturer SET manufacturer_id = 23, name = 'Google', sort_order=0;

How to add RSA key to authorized_keys file?

Make sure when executing Michael Krelin's solution you do the following

cat <your_public_key_file> >> ~/.ssh/authorized_keys

Note the double > without the double > the existing contents of authorized_keys will be over-written (nuked!) and that may not be desirable

HTTP requests and JSON parsing in Python

Use the requests library, pretty print the results so you can better locate the keys/values you want to extract, and then use nested for loops to parse the data. In the example I extract step by step driving directions.

import json, requests, pprint

url = ''

params = dict(

data = requests.get(url=url, params=params)
binary = data.content
output = json.loads(binary)

# test to see if the request was valid
#print output['status']

# output all of the results

# step-by-step directions
for route in output['routes']:
        for leg in route['legs']:
            for step in leg['steps']:
                print step['html_instructions']

Is there a way to avoid null check before the for-each loop iteration starts?

1) if list1 is a member of a class, create the list in the constructor so it's there and non-null though empty.

2) for (Object obj : list1 != null ? list1 : new ArrayList())

Google Maps Api v3 - find nearest markers

The formula above didn't work for me, but I used this without any issue. Pass your current location to the function, and loop through an array of markers to find the closest:

function find_closest_marker( lat1, lon1 ) {    
    var pi = Math.PI;
    var R = 6371; //equatorial radius
    var distances = [];
    var closest = -1;

    for( i=0;i<markers.length; i++ ) {  
        var lat2 = markers[i];
        var lon2 = markers[i].position.lng();

        var chLat = lat2-lat1;
        var chLon = lon2-lon1;

        var dLat = chLat*(pi/180);
        var dLon = chLon*(pi/180);

        var rLat1 = lat1*(pi/180);
        var rLat2 = lat2*(pi/180);

        var a = Math.sin(dLat/2) * Math.sin(dLat/2) + 
                    Math.sin(dLon/2) * Math.sin(dLon/2) * Math.cos(rLat1) * Math.cos(rLat2); 
        var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a)); 
        var d = R * c;

        distances[i] = d;
        if ( closest == -1 || d < distances[closest] ) {
            closest = i;

    // (debug) The closest marker is:

How to clear browsing history using JavaScript?

You cannot clear the browser history. It belongs to the user, not the developer. Also have a look at the MDN documentation.

Update: The link you were posting all over does not actually clear your browser history. It just prevents using the back button.

Groovy method with optional parameters

Can't be done as it stands... The code

def myMethod(pParm1='1', pParm2='2'){
    println "${pParm1}${pParm2}"

Basically makes groovy create the following methods:

Object myMethod( pParm1, pParm2 ) {
    println "$pParm1$pParm2"

Object myMethod( pParm1 ) {
    this.myMethod( pParm1, '2' )

Object myMethod() {
    this.myMethod( '1', '2' )

One alternative would be to have an optional Map as the first param:

def myMethod( Map map = [:], String mandatory1, String mandatory2 ){
    println "${mandatory1} ${mandatory2} ${map.parm1 ?: '1'} ${map.parm2 ?: '2'}"

myMethod( 'a', 'b' )                // prints 'a b 1 2'
myMethod( 'a', 'b', parm1:'value' ) // prints 'a b value 2'
myMethod( 'a', 'b', parm2:'2nd')    // prints 'a b 1 2nd'

Obviously, documenting this so other people know what goes in the magical map and what the defaults are is left to the reader ;-)

Escaping Strings in JavaScript

A variation of the function provided by Paolo Bergantino that works directly on String:

String.prototype.addSlashes = function() 
   //no need to do (str+'') anymore because 'this' can only be a string
   return this.replace(/[\\"']/g, '\\$&').replace(/\u0000/g, '\\0');

By adding the code above in your library you will be able to do:

var test = "hello single ' double \" and slash \\ yippie";


Following suggestions in the comments, whoever is concerned about conflicts amongst JavaScript libraries can add the following code:

   String.prototype.addSlashes = function()... 
   alert("Warning: String.addSlashes has already been declared elsewhere.");

Can't find android device using "adb devices" command

I had this problem today where the phone was charging when connected, but wasn't seen by the Mac. It turned out the micro USB cable that I was using was for charging only and didn't do data. Once I changed the USB cable it started working fine.

How do I monitor all incoming http requests?

Using Wireshark..

I have not tried this:

If that works, you could then filter for http/http contains GET/http contains POST traffic.

You might have to run two Wireshark instances, one capturing local, and one capturing remote. I'm not sure.

Run AVD Emulator without Android Studio

This is the commands on Mac

cd ~/Library/Android/Sdk/tools/bin && ./avdmanager list avd


cd ~/Library/Android/Sdk/tools && ./emulator -avd NAME_OF_YOUR_DEVICE

React Native fixed footer

import {Dimensions} from 'react-native'

const WIDTH = Dimensions.get('window').width;
const HEIGHT = Dimensions.get('window').height;

then on the write this styles

 position: 'absolute',
 top: HEIGHT-80,
 left: 0,
 right: 0,

worked like a charm

Is Google Play Store supported in avd emulators?

Starting from Android Studio 2.3.2 now you can create an AVD that has Play Store pre-installed on it. Currently, it is supported on the AVD's running

  • A device definition of Nexus 5 or 5X phone, or any Android Wear
  • A system image since Android 7.0 (API 24)

Official Source

For other emulators, you can try the solution mentioned in this answer.

Javascript : calling function from another file

Why don't you take a look to this answer

Including javascript files inside javascript files

In short you can load the script file with AJAX or put a script tag on the HTML to include it( before the script that uses the functions of the other script). The link I posted is a great answer and has multiple examples and explanations of both methods.

Console.log not working at all

Click on the restore button. console.log will start to work.

enter image description here

Check if list<t> contains any of another list

If both the list are too big and when we use lamda expression then it will take a long time to fetch . Better to use linq in this case to fetch parameters list:

var items = (from x in parameters
                join y in myStrings on x.Source equals y
                select x)

How to merge two files line by line in Bash

here's non-paste methods


awk 'BEGIN {OFS=" "}{
  getline line < "file2"
  print $0,line
} ' file1


exec 6<"file2"
while read -r line
    read -r f2line <&6
    echo "${line}${f2line}"
done <"file1"
exec 6<&-

Correct way of using log4net (logger naming)

Instead of naming my invoking class, I started using the following:

private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

In this way, I can use the same line of code in every class that uses log4net without having to remember to change code when I copy and paste. Alternatively, i could create a logging class, and have every other class inherit from my logging class.

Error pushing to GitHub - insufficient permission for adding an object to repository database

chmod should be chown, so the correct line is:

sudo chown -R gituser:gituser objects

Matplotlib: ValueError: x and y must have same first dimension

You should make x and y numpy arrays, not lists:

x = np.array([0.46,0.59,0.68,0.99,0.39,0.31,1.09,
y = np.array([0.315,0.383,0.452,0.650,0.279,0.215,0.727,0.512,

With this change, it produces the expect plot. If they are lists, m * x will not produce the result you expect, but an empty list. Note that m is anumpy.float64 scalar, not a standard Python float.

I actually consider this a bit dubious behavior of Numpy. In normal Python, multiplying a list with an integer just repeats the list:

In [42]: 2 * [1, 2, 3]
Out[42]: [1, 2, 3, 1, 2, 3]

while multiplying a list with a float gives an error (as I think it should):

In [43]: 1.5 * [1, 2, 3]
TypeError                                 Traceback (most recent call last)
<ipython-input-43-d710bb467cdd> in <module>()
----> 1 1.5 * [1, 2, 3]
TypeError: can't multiply sequence by non-int of type 'float'

The weird thing is that multiplying a Python list with a Numpy scalar apparently works:

In [45]: np.float64(0.5) * [1, 2, 3]
Out[45]: []

In [46]: np.float64(1.5) * [1, 2, 3]
Out[46]: [1, 2, 3]

In [47]: np.float64(2.5) * [1, 2, 3]
Out[47]: [1, 2, 3, 1, 2, 3]

So it seems that the float gets truncated to an int, after which you get the standard Python behavior of repeating the list, which is quite unexpected behavior. The best thing would have been to raise an error (so that you would have spotted the problem yourself instead of having to ask your question on Stackoverflow) or to just show the expected element-wise multiplication (in which your code would have just worked). Interestingly, addition between a list and a Numpy scalar does work:

In [69]: np.float64(0.123) + [1, 2, 3]
Out[69]: array([ 1.123,  2.123,  3.123])

What is the difference between properties and attributes in HTML?

After reading Sime Vidas's answer, I searched more and found a very straight-forward and easy-to-understand explanation in the angular docs.

HTML attribute vs. DOM property


Attributes are defined by HTML. Properties are defined by the DOM (Document Object Model).

  • A few HTML attributes have 1:1 mapping to properties. id is one example.

  • Some HTML attributes don't have corresponding properties. colspan is one example.

  • Some DOM properties don't have corresponding attributes. textContent is one example.

  • Many HTML attributes appear to map to properties ... but not in the way you might think!

That last category is confusing until you grasp this general rule:

Attributes initialize DOM properties and then they are done. Property values can change; attribute values can't.

For example, when the browser renders <input type="text" value="Bob">, it creates a corresponding DOM node with a value property initialized to "Bob".

When the user enters "Sally" into the input box, the DOM element value property becomes "Sally". But the HTML value attribute remains unchanged as you discover if you ask the input element about that attribute: input.getAttribute('value') returns "Bob".

The HTML attribute value specifies the initial value; the DOM value property is the current value.

The disabled attribute is another peculiar example. A button's disabled property is false by default so the button is enabled. When you add the disabled attribute, its presence alone initializes the button's disabled property to true so the button is disabled.

Adding and removing the disabled attribute disables and enables the button. The value of the attribute is irrelevant, which is why you cannot enable a button by writing <button disabled="false">Still Disabled</button>.

Setting the button's disabled property disables or enables the button. The value of the property matters.

The HTML attribute and the DOM property are not the same thing, even when they have the same name.

How To limit the number of characters in JTextField?

import javax.swing.text.PlainDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;

public class JTextFieldLimit extends PlainDocument {
  private int limit;

  JTextFieldLimit(int limit) {
   this.limit = limit;

  public void insertString( int offset, String  str, AttributeSet attr ) throws BadLocationException {
    if (str == null) return;

    if ((getLength() + str.length()) <= limit) {
      super.insertString(offset, str, attr);


import java.awt.*;
import javax.swing.*;

 public class DemoJTextFieldWithLimit extends JApplet{
   JTextField textfield1;
   JLabel label1;

   public void init() {
     getContentPane().setLayout(new FlowLayout());
     label1 = new JLabel("max 10 chars");
     textfield1 = new JTextField(15);
        (new JTextFieldLimit(10));

(first result from google)

ValidateAntiForgeryToken purpose, explanation and example

In ASP.Net Core anti forgery token is automatically added to forms, so you don't need to add @Html.AntiForgeryToken() if you use razor form element or if you use IHtmlHelper.BeginForm and if the form's method isn't GET.

It will generate input element for your form similar to this:

<input name="__RequestVerificationToken" type="hidden" 

And when user submits form this token is verified on server side if validation is enabled.

[ValidateAntiForgeryToken] attribute can be used against actions. Requests made to actions that have this filter applied are blocked unless the request includes a valid antiforgery token.

[AutoValidateAntiforgeryToken] attribute can be used against controllers. This attribute works identically to the ValidateAntiForgeryToken attribute, except that it doesn't require tokens for requests made using the following HTTP methods: GET HEAD OPTIONS TRACE

Additional information:

TypeError: 'undefined' is not a function (evaluating '$(document)')

I ran into this problem also when including jQuery in my page header, not realizing the host was already including it in the page automatically. So load your page live and check the source to see if jQuery is being linked in.

How to convert base64 string to image?

Try this:

import base64
imgdata = base64.b64decode(imgstring)
filename = 'some_image.jpg'  # I assume you have a way of picking unique filenames
with open(filename, 'wb') as f:
# f gets closed when you exit the with statement
# Now save the value of filename to your database

Partly JSON unmarshal into a map in Go

Here is an elegant way to do similar thing. But why do partly JSON unmarshal? That doesn't make sense.

  1. Create your structs for the Chat.
  2. Decode json to the Struct.
  3. Now you can access everything in Struct/Object easily.

Look below at the working code. Copy and paste it.

import (
   "encoding/json" // Encoding and Decoding Package

var messeging = `{
    "msg":"Trying to send a message"

type SendMsg struct {
   User string `json:"user"`
   Msg  string `json:"msg"`

 type Chat struct {
   Say     string   `json:"say"`
   SendMsg *SendMsg `json:"sendMsg"`

func main() {
  /** Clean way to solve Json Decoding in Go */
  /** Excellent solution */

   var chat Chat
   r := bytes.NewReader([]byte(messeging))
   chatErr := json.NewDecoder(r).Decode(&chat)


 func errHandler(err error) {
   if err != nil {

Go playground

Environment variables in Eclipse

I was able to set the env. variables by sourcing (source command inside the shell (ksh) scirpt) the file that was settign them. Then I called the .ksh script from the external Tools

Pycharm/Python OpenCV and CV2 install error

I rather use Virtualenv to install such packages rather than the entire system, saves time and effort rather than building from source.

I use virtualenvwrapper

Windows user can download

pip install virtualenvwrapper-win

Linux follow

pip install opencv-python


If processing a video is required

pip install opencv-contrib-python


If you do not need GUI in Opencv

pip install opencv-contrib-python-headless


How do I concatenate text in a query in sql server?

If you are using SQL Server 2005 or greater, depending on the size of the data in the Notes field, you may want to consider casting to nvarchar(max) instead of casting to a specific length which could result in string truncation.

Select Cast(notes as nvarchar(max)) + 'SomeText' From NotesTable a

Cannot make Project Lombok work on Eclipse

After adding lombok and restarting eclipse or spring tools my project still failed to recognize getters and setters. Red markers everywhere!

The solution: right-click your project, go to Maven and select Update Project

After hours of searching and trying random solution, I find this to be the only solution that worked for me.

enter image description here

What dependency is missing for org.springframework.web.bind.annotation.RequestMapping?

Thanks above all of you contributions! however for my case I finally realized that my dependency above "spring-web" was destroyed on my .m2/repository/org/springframework/spring-web, I just deleted the folder and update Maven again. it got fixed.

How to get the caller class in Java

The error message the OP is encountering is just an Eclipse feature. If you are willing to tie your code to a specific maker (and even version) of the JVM, you can effectively use method sun.reflect.Reflection.getCallerClass(). You can then compile the code outside of Eclipse or configure it not to consider this diagnostic an error.

The worse Eclipse configuration is to disable all occurrences of the error by:

Project Properties / Java Compiler / Errors/Warnings / Enable project specific settings set to checked / Deprecated and restrited API / Forbidden reference (access rules) set to Warning or Ignore.

The better Eclipse configuration is to disable a specific occurrence of the error by:

Project Properties / Java Build Path / Libraries / JRE System Library expand / Access rules: select / Edit... / Add... / Resolution: set to Discouraged or Accessible / Rule Pattern set to sun/reflect/Reflection.

CSS Div Background Image Fixed Height 100% Width

But the thing is that the .chapter class is not dynamic you're declaring a height:1200px

so it's better to use background:cover and set with media queries specific height's for popular resolutions.

Problem with converting int to string in Linq to entities

var items = from c in contacts
select new ListItem
    Value = String.Concat(c.ContactId), //This Works in Linq to Entity!
    Text = c.Name

I found that SqlFunctions.StringConvert((double)c.Age) did not work for me either the field is of type Nullable<Int32>

Took me a lot of searching over the last few days of trial and error to find this.

I hope this helps a few coders out there.

Edit line thickness of CSS 'underline' attribute

My Solution :

    display: inline-block;
    border-bottom: 1px solid;
    padding-bottom: 0;
    line-height: 70%;

You can adjust underline position with line-height value, underline thickness and style with border-bottom.

Beware to disable default underline behavior if you want to underline an href.

What is the difference between 'java', 'javaw', and 'javaws'?

java.exe is associated with the console, whereas javaw.exe doesn't have any such association. So, when java.exe is run, it automatically opens a command prompt window where output and error streams are shown.

Get Category name from Post ID

echo '<p>'. get_the_category( $id )[0]->name .'</p>';

is what you maybe looking for.

Which loop is faster, while or for?

Set the loop iterations to 10,000.

Find the time in milliseconds>Run Loop>find time in milliseconds and subtract the first timer.

Do it for both codes, what ever one has the lowest milliseconds it runs faster. You might want to run the test multiple times and average them out to reduce the likelihood of background processes influencing the test.

You are likely to get really similar times on both of them, but I am interested to see if one is always just slightly faster.

T-SQL: Opposite to string concatenation - how to split string into multiple records

I use this function (SQL Server 2005 and above).

create function [dbo].[Split]
    @string nvarchar(4000),
    @delimiter nvarchar(10)
returns @table table
    [Value] nvarchar(4000)
    declare @nextString nvarchar(4000)
    declare @pos int, @nextPos int

    set @nextString = ''
    set @string = @string + @delimiter

    set @pos = charindex(@delimiter, @string)
    set @nextPos = 1
    while (@pos <> 0)
        set @nextString = substring(@string, 1, @pos - 1)

        insert into @table

        set @string = substring(@string, @pos + len(@delimiter), len(@string))
        set @nextPos = @pos
        set @pos = charindex(@delimiter, @string)

How to prevent rm from reporting that a file was not found?

\rm -f file will never report not found.

What's the purpose of git-mv?

From the official GitFaq:

Git has a rename command git mv, but that is just a convenience. The effect is indistinguishable from removing the file and adding another with different name and the same content

Writing to a file in a for loop

The main problem was that you were opening/closing files repeatedly inside your loop.

Try this approach:

with open('new.txt') as text_file, open('xyz.txt', 'w') as myfile:  
    for line in text_file:
        var1, var2 = line.split(",");

We open both files at once and because we are using with they will be automatically closed when we are done (or an exception occurs). Previously your output file was repeatedly openend inside your loop.

We are also processing the file line-by-line, rather than reading all of it into memory at once (which can be a problem when you deal with really big files).

Note that write() doesn't append a newline ('\n') so you'll have to do that yourself if you need it (I replaced your writelines() with write() as you are writing a single item, not a list of items).

When opening a file for rread, the 'r' is optional since it's the default mode.

For loop in multidimensional javascript array

You can do something like this:

var cubes = [
 [1, 2, 3],
 [4, 5, 6],    
 [7, 8, 9],

for(var i = 0; i < cubes.length; i++) {
    var cube = cubes[i];
    for(var j = 0; j < cube.length; j++) {
        display("cube[" + i + "][" + j + "] = " + cube[j]);

Working jsFiddle:

The output of the above:

cube[0][0] = 1
cube[0][1] = 2
cube[0][2] = 3
cube[1][0] = 4
cube[1][1] = 5
cube[1][2] = 6
cube[2][0] = 7
cube[2][1] = 8
cube[2][2] = 9

How to perform a for-each loop over all the files under a specified path?

Here is a better way to loop over files as it handles spaces and newlines in file names:


find . -type f -iname "*.txt" -print0 | while IFS= read -r -d $'\0' line; do
    echo "$line"
    ls -l "$line"    

How to install Visual C++ Build tools?

The current version (2019/03/07) is Build Tools for Visual Studio 2017. It's an online installer, you need to include at least the individual components:

  • VC++ 2017 version xx.x tools
  • Windows SDK to use standard libraries.

Java HashMap performance optimization / alternative

First you should check that you are using Map correctly, good hashCode() method for keys, initial capacity for Map, right Map implementation etc. like many other answers describe.

Then I would suggest using a profiler to see what is actually happening and where the execution time is spent. Is, for example, hashCode() method executed for billions of times?

If that doesn't help, how about using something like EHCache or memcached? Yes, they are products for caching but you could configure them so that they will have enough capacity and will never evict any values from cache storage.

Another option would be some database engine that is lighter weight than full SQL RDBMS. Something like Berkeley DB, maybe.

Note, that I have personally no experience of these products' performance, but they could be worth the try.

Finding the path of the program that will execute from the command line in Windows

Use the where command. The first result in the list is the one that will execute.

C:\> where notepad

According to this blog post, where.exe is included with Windows Server 2003 and later, so this should just work with Vista, Win 7, et al.

On Linux, the equivalent is the which command, e.g. which ssh.

SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch

Once you have established that they don't match, you still have a problem -- what to do about it. Often, the certificate may merely be assembled incorrectly. When a CA signs your certificate, they send you a block that looks something like


they'll also send you a bundle (often two certificates) that represent their authority to grant you a certificate. this will look something like


except that unfortunately, they won't be so clearly labeled.

a common practice, then, is to bundle these all up into one file -- your certificate, then the signing certificates. But since they aren't easily distinguished, it sometimes happens that someone accidentally puts them in the other order -- signing certs, then the final cert -- without noticing. In that case, your cert will not match your key.

You can test to see what the cert thinks it represents by running

openssl x509 -noout -text -in yourcert.cert

Near the top, you should see "Subject:" and then stuff that looks like your data. If instead it lookslike your CA, your bundle is probably in the wrong order; you might try making a backup, and then moving the last cert to the beginning, hoping that is the one that is your cert.

If this doesn't work, you might just have to get the cert re-issued. When I make a CSR, I like to clearly label what server it's for (instead of just ssl.key or server.key) and make a copy of it with the date in the name, like mydomain.20150306.key etc. that way they private and public key pairs are unlikely to get mixed up with another set.

Should jQuery's $(form).submit(); not trigger onSubmit within the form tag?

I found this question serval years ago.

recently I tried to "rewrite" the submit method. below is my code

window.onload= function (){
for(var i= 0;i<document.forms.length;i++){
    (function (p){
        var form= document.forms[i];
        var originFn= form.submit;
        form.submit=function (){
            //do something you like
            alert("submitting "" using submit method !");
        form.onsubmit= function (){
            alert("submitting "" with onsubmit event !");



<form method="get" action="" id="form1">
<input type="submit" value="??form1" />
<input type="button" name="" id="" value="button????1" onclick="document.forms[0].submit();" /></form>

It did in IE,but failed in other browsers for the same reason as "cletus"

Function return value in PowerShell

The following simply returns 4 as an answer. When you replace the add expressions for strings it returns the first string.

Function StartingMain {
  $a = 1 + 3
  $b = 2 + 5
  $c = 3 + 7
  Return $a

Function StartingEnd($b) {
  Write-Host $b


This can also be done for an array. The example below will return "Text 2"

Function StartingMain {
  $a = ,@("Text 1","Text 2","Text 3")
  Return $a

Function StartingEnd($b) {
  Write-Host $b[1]


Note that you have to call the function below the function itself. Otherwise, the first time it runs it will return an error that it doesn't know what "StartingMain" is.

What does servletcontext.getRealPath("/") mean and when should I use it

A web application's context path is the directory that contains the web application's WEB-INF directory. It can be thought of as the 'home' of the web app. Often, when writing web applications, it can be important to get the actual location of this directory in the file system, since this allows you to do things such as read from files or write to files.

This location can be obtained via the ServletContext object's getRealPath() method. This method can be passed a String parameter set to File.separator to get the path using the operating system's file separator ("/" for UNIX, "\" for Windows).

Java Programming: call an exe from Java and passing parameters

Pass your arguments in constructor itself.

Process process = new ProcessBuilder("C:\\PathToExe\\MyExe.exe","param1","param2").start();

How to specify a port number in SQL Server connection string?

The correct SQL connection string for SQL with specify port is use comma between ip address and port number like following pattern:,yyyy

Can an Android App connect directly to an online mysql database

You can use PHP, JSP, ASP or any other server side script to connect with mysql database and and return JSON data that you can parse it to in your android app this link how to do it

get current page from url

Path.GetFileName( Request.Url.AbsolutePath )

Using SELECT result in another SELECT

You are missing table NewScores, so it can't be found. Just join this table.

If you really want to avoid joining it directly you can replace NewScores.NetScore with SELECT NetScore FROM NewScores WHERE {conditions on which they should be matched}

java.lang.NoClassDefFoundError: org.slf4j.LoggerFactory

I also had the similar problem. I had a maven project and was testing rabbitmq. Firstly it showed me the similar error then I added all the SLF4J dependencies in the maven project and then error changed to "Maven SLF4J: Class path contains multiple SLF4J bindings". Here is the complete list of dependencies from pom.xlm


It worked finally.

How do I create dynamic properties in C#?

Create a Hashtable called "Properties" and add your properties to it.

Reset select2 value and show placeholder

You can clear te selection by


But it wont turn you back to your placeholder.

So its a half solution

Count work days between two dates

None of the functions above work for the same week or deal with holidays. I wrote this:

create FUNCTION [dbo].[ShiftHolidayToWorkday](@date date)
    IF DATENAME( dw, @Date ) = 'Saturday'
        SET @Date = DATEADD(day, - 1, @Date)

    ELSE IF DATENAME( dw, @Date ) = 'Sunday'
        SET @Date = DATEADD(day, 1, @Date)

    RETURN @date

create FUNCTION [dbo].[GetHoliday](@date date)
RETURNS varchar(50)
    declare @s varchar(50)

    SELECT @s = CASE
        WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]  ) + '-01-01') = @date THEN 'New Year'
        WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]+1) + '-01-01') = @date THEN 'New Year'
        WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]  ) + '-07-04') = @date THEN 'Independence Day'
        WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]  ) + '-12-25') = @date THEN 'Christmas Day'
        --WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]) + '-12-31') = @date THEN 'New Years Eve'
        --WHEN dbo.ShiftHolidayToWorkday(CONVERT(varchar, [Year]) + '-11-11') = @date THEN 'Veteran''s Day'

        WHEN [Month] = 1  AND [DayOfMonth] BETWEEN 15 AND 21 AND [DayName] = 'Monday' THEN 'Martin Luther King Day'
        WHEN [Month] = 5  AND [DayOfMonth] >= 25             AND [DayName] = 'Monday' THEN 'Memorial Day'
        WHEN [Month] = 9  AND [DayOfMonth] <= 7              AND [DayName] = 'Monday' THEN 'Labor Day'
        WHEN [Month] = 11 AND [DayOfMonth] BETWEEN 22 AND 28 AND [DayName] = 'Thursday' THEN 'Thanksgiving Day'
        WHEN [Month] = 11 AND [DayOfMonth] BETWEEN 23 AND 29 AND [DayName] = 'Friday' THEN 'Day After Thanksgiving'
    FROM (
            [Year] = YEAR(@date),
            [Month] = MONTH(@date),
            [DayOfMonth] = DAY(@date),
            [DayName]   = DATENAME(weekday,@date)
    ) c

    RETURN @s

create FUNCTION [dbo].GetHolidays(@year int)
    select dt, dbo.GetHoliday(dt) as Holiday
    from (
        select dateadd(day, number, convert(varchar,@year) + '-01-01') dt
        from master..spt_values 
        where type='p' 
        ) d
    where year(dt) = @year and dbo.GetHoliday(dt) is not null

create proc UpdateHolidaysTable

if not exists(select TABLE_NAME from INFORMATION_SCHEMA.TABLES where TABLE_NAME = 'Holidays')
    create table Holidays(dt date primary key clustered, Holiday varchar(50))

declare @year int
set @year = 1990

while @year < year(GetDate()) + 20
    insert into Holidays(dt, Holiday)
    select a.dt, a.Holiday
    from dbo.GetHolidays(@year) a
        left join Holidays b on b.dt = a.dt
    where b.dt is null

    set @year = @year + 1

create FUNCTION [dbo].[GetWorkDays](@StartDate DATE = NULL, @EndDate DATE = NULL)
    IF @StartDate IS NULL OR @EndDate IS NULL
        RETURN  0

    IF @StartDate >= @EndDate 
        RETURN  0

    DECLARE @Days int
    SET @Days = 0

    IF year(@StartDate) * 100 + datepart(week, @StartDate) = year(@EndDate) * 100 + datepart(week, @EndDate) 
        --same week
        select @Days = (DATEDIFF(dd, @StartDate, @EndDate))
      - (CASE WHEN DATENAME(dw, @StartDate) = 'Sunday' THEN 1 ELSE 0 END)
      - (CASE WHEN DATENAME(dw, @EndDate) = 'Saturday' THEN 1 ELSE 0 END)
      - (select count(*) from Holidays where dt between @StartDate and @EndDate)
        --diff weeks
        select @Days = (DATEDIFF(dd, @StartDate, @EndDate) + 1)
      - (DATEDIFF(wk, @StartDate, @EndDate) * 2)
      - (CASE WHEN DATENAME(dw, @StartDate) = 'Sunday' THEN 1 ELSE 0 END)
      - (CASE WHEN DATENAME(dw, @EndDate) = 'Saturday' THEN 1 ELSE 0 END)
      - (select count(*) from Holidays where dt between @StartDate and @EndDate)
    RETURN  @Days

How to disable Home and other system buttons in Android?

Sorry for answering after 2-3 years. but you can hide activity of all system buttons. Just check this my answers How to disable virtual home button in any activity?.

Detect Safari using jQuery

For checking Safari I used this:

$.browser.safari = ($.browser.webkit && !(/chrome/.test(navigator.userAgent.toLowerCase())));
if ($.browser.safari) {
    alert('this is safari');

It works correctly.

How to replace string in Groovy

You need to escape the backslash \:

println yourString.replace("\\", "/")

How to stop IIS asking authentication for default website on localhost

  1. Add Admin user with password
  2. Go to wwwroot props
  3. Give this user a full access to this folder and its children
  4. Change the user of the AppPool to the added user using this article
  5. Change the User of the website using this article Put the same username and password you have created at step (1).

It is working now congrats

Java error - "invalid method declaration; return type required"

I had a similar issue when adding a class to the main method. Turns out it wasn't an issue, it was me not checking my spelling. So, as a noob, I learned that mis-spelling can and will mess things up. These posts helped me "see" my mistake and all is good now.

Accessing localhost of PC from USB connected Android mobile device

Problem I faced maybe it will help some one, I was working long time where my pc and android device connected to the same WiFi network and the android device connected via the IPV4 address of the pc with opened port 8080 trought the fire wall.

ONE DAY : I installed Genymotion emulator in order to debug UI on different screens. THANKS to Genymotion/Virtualbox network configurations it ruined my WiFi adapter.

The fix was to reconfigure IPV4/TCP settings on the WiFi netwrok adapter :

enter image description here

Completely cancel a rebase

You are lucky that you didn't complete the rebase, so you can still do git rebase --abort. If you had completed the rebase (it rewrites history), things would have been much more complex. Consider tagging the tips of branches before doing potentially damaging operations (particularly history rewriting), that way you can rewind if something blows up.

How to change workspace and build record Root Directory on Jenkins?

By default, Jenkins stores all of its data in this directory on the file system.

There are a few ways to change the Jenkins home directory:

  • Edit the JENKINS_HOME variable in your Jenkins configuration file (e.g. /etc/sysconfig/jenkins on Red Hat Linux).
  • Use your web container's admin tool to set the JENKINS_HOME environment variable.
  • Set the environment variable JENKINS_HOME before launching your web container, or before launching Jenkins directly from the WAR file.
  • Set the JENKINS_HOME Java system property when launching your web container, or when launching Jenkins directly from the WAR file.
  • Modify web.xml in jenkins.war (or its expanded image in your web container). This is not recommended. This value cannot be changed while Jenkins is running. It is shown here to help you ensure that your configuration is taking effect.

JPA and Hibernate - Criteria vs. JPQL or HQL

I mostly prefer Criteria Queries for dynamic queries. For example it is much easier to add some ordering dynamically or leave some parts (e.g. restrictions) out depending on some parameter.

On the other hand I'm using HQL for static and complex queries, because it's much easier to understand/read HQL. Also, HQL is a bit more powerful, I think, e.g. for different join types.

Reloading/refreshing Kendo Grid

The easiest way out to refresh is using the refresh() function. Which goes like:


while you can also refresh the data source using this command:


The latter actually reloads the data source of the grid. The use of both can be done according to your need and requirement.

Case Statement Equivalent in R

I see no proposal for 'switch'. Code example (run it):

x <- "three"
y <- 0
       one = {y <- 5},
       two = {y <- 12},
       three = {y <- 432})

JPA OneToMany and ManyToOne throw: Repeated column in mapping for entity column (should be mapped with insert="false" update="false")

I am not really sure about your question (the meaning of "empty table" etc, or how mappedBy and JoinColumn were not working).

I think you were trying to do a bi-directional relationships.

First, you need to decide which side "owns" the relationship. Hibernate is going to setup the relationship base on that side. For example, assume I make the Post side own the relationship (I am simplifying your example, just to keep things in point), the mapping will look like:

(Wish the syntax is correct. I am writing them just by memory. However the idea should be fine)

public class User{
    @OneToMany(fetch=FetchType.LAZY, cascade = CascadeType.ALL, mappedBy="user")
    private List<Post> posts;

public class Post {
    private User user;

By doing so, the table for Post will have a column user_id which store the relationship. Hibernate is getting the relationship by the user in Post (Instead of posts in User. You will notice the difference if you have Post's user but missing User's posts).

You have mentioned mappedBy and JoinColumn is not working. However, I believe this is in fact the correct way. Please tell if this approach is not working for you, and give us a bit more info on the problem. I believe the problem is due to something else.


Just a bit extra information on the use of mappedBy as it is usually confusing at first. In mappedBy, we put the "property name" in the opposite side of the bidirectional relationship, not table column name.

How to get a cross-origin resource sharing (CORS) post request working

This is a summary of what worked for me:

Define a new function (wrapped $.ajax to simplify):

jQuery.postCORS = function(url, data, func) {
  if(func == undefined) func = function(){};
  return $.ajax({
    type: 'POST', 
    url: url, 
    data: data, 
    dataType: 'json', 
    contentType: 'application/x-www-form-urlencoded', 
    xhrFields: { withCredentials: true }, 
    success: function(res) { func(res) }, 
    error: function() { 


$.postCORS("",{ x : 1 },function(obj){
      if(obj.ok) {

Also works with .done,.fail,etc:

$.postCORS("",{ x : 1 }).done(function(obj){
      if(obj.ok) {

Server side (in this case where is hosted), set these headers (added some sample code in PHP):

header('Access-Control-Allow-Credentials: true');
header('Access-Control-Max-Age: 604800');
header("Content-type: application/json");
$array = array("ok" => $_POST["x"]);
echo json_encode($array);

This is the only way I know to truly POST cross-domain from JS.

JSONP converts the POST into GET which may display sensitive information at server logs.

Why use sys.path.append(path) instead of sys.path.insert(1, path)?

If you really need to use sys.path.insert, consider leaving sys.path[0] as it is:

sys.path.insert(1, path_to_dev_pyworkbooks)

This could be important since 3rd party code may rely on sys.path documentation conformance:

As initialized upon program startup, the first item of this list, path[0], is the directory containing the script that was used to invoke the Python interpreter.

What is the maximum possible length of a .NET string?

The theoretical limit may be 2,147,483,647, but the practical limit is nowhere near that. Since no single object in a .NET program may be over 2GB and the string type uses UTF-16 (2 bytes for each character), the best you could do is 1,073,741,823, but you're not likely to ever be able to allocate that on a 32-bit machine.

This is one of those situations where "If you have to ask, you're probably doing something wrong."

bootstrap popover not showing on top of all elements

If data-container="body" not works than try other two properties:

data-container="body" style="z-index:1000; position:relative"

z-index should be max limit.

Arrays.asList() of an array

I think you have found an example where auto-boxing doesn't really work. Because Arrays.asList(T... a) has a varargs parameter the compiler apparently considers the int[] and returns a List<int[]> with a single element in it.

You should change the method into this:

public int getTheNumber(Integer[] factors) {
    ArrayList<Integer> f = new ArrayList<Integer>(Arrays.asList(factors));  
    return f.get(0) * f.get(f.size() - 1);

and possibly add this for compatibility

public int getTheNumber(int[] factors) {
    Integer[] factorsInteger = new Integer[factors.length];
    for(int ii=0; ii<factors.length; ++ii) {
        factorsInteger[ii] = factors[ii];

    return getTheNumber(factorsInteger);

Call php function from JavaScript

The only way to execute PHP from JS is AJAX. You can send data to server (for eg, GET /ajax.php?do=someFunction) then in ajax.php you write:

function someFunction() {
    echo 'Answer';

if ($_GET['do'] === "someFunction") {

and then, catch the answer with JS (i'm using jQuery for making AJAX requests)

Probably you'll need some format of answer. See JSON or XML, but JSON is easy to use with JavaScript. In PHP you can use function json_encode($array); which gets array as argument.

How to list installed packages from a given repo using yum


yum list installed | grep reponame

On one of my servers:

yum list installed | grep remi
ImageMagick2.x86_64                       installed
memcache.x86_64                          1.4.5-2.el5.remi             installed
mysql.x86_64                              5.1.54-1.el5.remi            installed
mysql-devel.x86_64                        5.1.54-1.el5.remi            installed
mysql-libs.x86_64                         5.1.54-1.el5.remi            installed
mysql-server.x86_64                       5.1.54-1.el5.remi            installed
mysqlclient15.x86_64                      5.0.67-1.el5.remi            installed
php.x86_64                                5.3.5-1.el5.remi             installed
php-cli.x86_64                            5.3.5-1.el5.remi             installed
php-common.x86_64                         5.3.5-1.el5.remi             installed
php-domxml-php4-php5.noarch               1.21.2-1.el5.remi            installed
php-fpm.x86_64                            5.3.5-1.el5.remi             installed
php-gd.x86_64                             5.3.5-1.el5.remi             installed
php-mbstring.x86_64                       5.3.5-1.el5.remi             installed
php-mcrypt.x86_64                         5.3.5-1.el5.remi             installed
php-mysql.x86_64                          5.3.5-1.el5.remi             installed
php-pdo.x86_64                            5.3.5-1.el5.remi             installed
php-pear.noarch                           1:1.9.1-6.el5.remi           installed
php-pecl-apc.x86_64                       3.1.6-1.el5.remi             installed
php-pecl-imagick.x86_64                   3.0.1-1.el5.remi.1           installed
php-pecl-memcache.x86_64                  3.0.5-1.el5.remi             installed
php-pecl-xdebug.x86_64                    2.1.0-1.el5.remi             installed
php-soap.x86_64                           5.3.5-1.el5.remi             installed
php-xml.x86_64                            5.3.5-1.el5.remi             installed
remi-release.noarch                       5-8.el5.remi                 installed

It works.

Get index of array element faster than O(n)

Is there a good reason not to use a hash? Lookups are O(1) vs. O(n) for the array.

TypeScript, Looping through a dictionary

Ians Answer is good, but you should use const instead of let for the key because it never gets updated.

for (const key in myDictionary) {
    let value = myDictionary[key];
    // Use `key` and `value`

How to set up file permissions for Laravel?

For Laravel developers, directory issues can be a little bit pain. In my application, I was creating directories on the fly and moving files to this directory in my local environment successfully. Then on server, I was getting errors while moving files to newly created directory.

Here are the things that I have done and got a successful result at the end.

  1. sudo find /path/to/your/laravel/root/directory -type f -exec chmod 664 {} \;
    sudo find /path/to/your/laravel/root/directory -type d -exec chmod 775 {} \;
  2. chcon -Rt httpd_sys_content_rw_t /path/to/my/file/upload/directory/in/laravel/project/
  3. While creating the new directory on the fly, I used the command mkdir($save_path, 0755, true);

After making those changes on production server, I successfully created new directories and move files to them.

Finally, if you use File facade in Laravel you can do something like this: File::makeDirectory($save_path, 0755, true);

How to calculate mean, median, mode and range from a set of numbers

public class Mode {
    public static void main(String[] args) {
        int[] unsortedArr = new int[] { 3, 1, 5, 2, 4, 1, 3, 4, 3, 2, 1, 3, 4, 1 ,-1,-1,-1,-1,-1};
        Map<Integer, Integer> countMap = new HashMap<Integer, Integer>();

        for (int i = 0; i < unsortedArr.length; i++) {
            Integer value = countMap.get(unsortedArr[i]);

            if (value == null) {
                countMap.put(unsortedArr[i], 0);
            } else {
                int intval = value.intValue();
                countMap.put(unsortedArr[i], intval);


        int max = getMaxFreq(countMap.values());
        List<Integer> modes = new ArrayList<Integer>();

        for (Entry<Integer, Integer> entry : countMap.entrySet()) {
            int value = entry.getValue();
            if (value == max)

    public static int getMaxFreq(Collection<Integer> valueSet) {
        int max = 0;
        boolean setFirstTime = false;

        for (Iterator iterator = valueSet.iterator(); iterator.hasNext();) {
            Integer integer = (Integer);

            if (!setFirstTime) {
                max = integer;
                setFirstTime = true;
            if (max < integer) {
                max = integer;
        return max;

Test data

Modes {1,3} for { 3, 1, 5, 2, 4, 1, 3, 4, 3, 2, 1, 3, 4, 1 };
Modes {-1} for { 3, 1, 5, 2, 4, 1, 3, 4, 3, 2, 1, 3, 4, 1 ,-1,-1,-1,-1,-1};

What's the best way to parse command line arguments?

Using docopt

Since 2012 there is a very easy, powerful and really cool module for argument parsing called docopt. Here is an example taken from its documentation:

"""Naval Fate.

Usage: ship new <name>... ship <name> move <x> <y> [--speed=<kn>] ship shoot <x> <y> mine (set|remove) <x> <y> [--moored | --drifting] (-h | --help) --version

  -h --help     Show this screen.
  --version     Show version.
  --speed=<kn>  Speed in knots [default: 10].
  --moored      Moored (anchored) mine.
  --drifting    Drifting mine.

from docopt import docopt

if __name__ == '__main__':
    arguments = docopt(__doc__, version='Naval Fate 2.0')

So this is it: 2 lines of code plus your doc string which is essential and you get your arguments parsed and available in your arguments object.

Using python-fire

Since 2017 there's another cool module called python-fire. It can generate a CLI interface for your code with you doing zero argument parsing. Here's a simple example from the documentation (this small program exposes the function double to the command line):

import fire

class Calculator(object):

  def double(self, number):
    return 2 * number

if __name__ == '__main__':

From the command line, you can run:

> double 10
> double --number=15

Using momentjs to convert date to epoch then back to date

There are a few things wrong here:

  • First, terminology. "Epoch" refers to the starting point of something. The "Unix Epoch" is Midnight, January 1st 1970 UTC. You can't convert an arbitrary "date string to epoch". You probably meant "Unix Time", which is often erroneously called "Epoch Time".

  • .unix() returns Unix Time in whole seconds, but the default moment constructor accepts a timestamp in milliseconds. You should instead use .valueOf() to return milliseconds. Note that calling .unix()*1000 would also work, but it would result in a loss of precision.

  • You're parsing a string without providing a format specifier. That isn't a good idea, as values like 1/2/2014 could be interpreted as either February 1st or as January 2nd, depending on the locale of where the code is running. (This is also why you get the deprecation warning in the console.) Instead, provide a format string that matches the expected input, such as:

    moment("10/15/2014 9:00", "M/D/YYYY H:mm")
  • .calendar() has a very specific use. If you are near to the date, it will return a value like "Today 9:00 AM". If that's not what you expected, you should use the .format() function instead. Again, you may want to pass a format specifier.

  • To answer your questions in comments, No - you don't need to call .local() or .utc().

Putting it all together:

var ts = moment("10/15/2014 9:00", "M/D/YYYY H:mm").valueOf();
var m = moment(ts);
var s = m.format("M/D/YYYY H:mm");
alert("Values are: ts = " + ts + ", s = " + s);

On my machine, in the US Pacific time zone, it results in:

Values are: ts = 1413388800000, s = 10/15/2014 9:00

Since the input value is interpreted in terms of local time, you will get a different value for ts if you are in a different time zone.

Also note that if you really do want to work with whole seconds (possibly losing precision), moment has methods for that as well. You would use .unix() to return the timestamp in whole seconds, and moment.unix(ts) to parse it back to a moment.

var ts = moment("10/15/2014 9:00", "M/D/YYYY H:mm").unix();
var m = moment.unix(ts);

How do I lowercase a string in Python?

Don't try this, totally un-recommend, don't do this:

import string
print(''.join([string.ascii_lowercase[string.ascii_uppercase.index(i)] for i in s]))



Since no one wrote it yet you can use swapcase (so uppercase letters will become lowercase, and vice versa) (and this one you should use in cases where i just mentioned (convert upper to lower, lower to upper)):




How to return a file (FileContentResult) in ASP.NET WebAPI

I am not exactly sure which part to blame, but here's why MemoryStream doesn't work for you:

As you write to MemoryStream, it increments it's Position property. The constructor of StreamContent takes into account the stream's current Position. So if you write to the stream, then pass it to StreamContent, the response will start from the nothingness at the end of the stream.

There's two ways to properly fix this:

1) construct content, write to stream

public HttpResponseMessage Test()
    var stream = new MemoryStream();
    var response = Request.CreateResponse(HttpStatusCode.OK);
    response.Content = new StreamContent(stream);
    // ...
    // stream.Write(...);
    // ...
    return response;

2) write to stream, reset position, construct content

public HttpResponseMessage Test()
    var stream = new MemoryStream();
    // ...
    // stream.Write(...);
    // ...
    stream.Position = 0;

    var response = Request.CreateResponse(HttpStatusCode.OK);
    response.Content = new StreamContent(stream);
    return response;

2) looks a little better if you have a fresh Stream, 1) is simpler if your stream does not start at 0

How can I convert a stack trace to a string?

Printing stack trace to string


public class StackTraceUtils {
    public static String stackTraceToString(StackTraceElement[] stackTrace) {
        StringWriter sw = new StringWriter();
        printStackTrace(stackTrace, new PrintWriter(sw));
        return sw.toString();
    public static void printStackTrace(StackTraceElement[] stackTrace, PrintWriter pw) {
        for(StackTraceElement stackTraceEl : stackTrace) {

It's useful when you want to print the current thread stack trace without creating instance of Throwable - but note that creating new Throwable and getting stack trace from there is actually faster and cheaper than calling Thread.getStackTrace.

How do I pass variables and data from PHP to JavaScript?


$fruits = array("apple" => "yellow", "strawberry" => "red", "kiwi" => "green");
    var color = <?php echo json_encode($fruits) ?>;
<script src="../yourexternal.js"></script>

JS (yourexternal.js)

alert("The apple color is" + color['apple'] + ", the strawberry color is " + color['strawberry'] + " and the kiwi color is " + color['kiwi'] + ".");


The apple color is yellow, the strawberry color is red and the kiwi color is green.

Double vs. BigDecimal?

If you write down a fractional value like 1 / 7 as decimal value you get

1/7 = 0.142857142857142857142857142857142857142857...

with an infinite sequence of 142857. Since you can only write a finite number of digits you will inevitably introduce a rounding (or truncation) error.

Numbers like 1/10 or 1/100 expressed as binary numbers with a fractional part also have an infinite number of digits after the decimal point:

1/10 = binary 0.0001100110011001100110011001100110...

Doubles store values as binary and therefore might introduce an error solely by converting a decimal number to a binary number, without even doing any arithmetic.

Decimal numbers (like BigDecimal), on the other hand, store each decimal digit as is (binary coded, but each decimal on its own). This means that a decimal type is not more precise than a binary floating point or fixed point type in a general sense (i.e. it cannot store 1/7 without loss of precision), but it is more accurate for numbers that have a finite number of decimal digits as is often the case for money calculations.

Java's BigDecimal has the additional advantage that it can have an arbitrary (but finite) number of digits on both sides of the decimal point, limited only by the available memory.

Removing border from table cells

Change your table declaration to:

<table style="border: 1px dashed; width: 500px;">

Here is the sample in action:

How to loop over a Class attributes in Java?

Simple way to iterate over class fields and obtain values from object:

 Class<?> c = obj.getClass();
 Field[] fields = c.getDeclaredFields();
 Map<String, Object> temp = new HashMap<String, Object>();

 for( Field field : fields ){
      try {
           temp.put(field.getName().toString(), field.get(obj));
      } catch (IllegalArgumentException e1) {
      } catch (IllegalAccessException e1) {

Parse string to DateTime in C#

You can also use XmlConvert.ToDateString

var dateStr = "2011-03-21 13:26";
var parsedDate = XmlConvert.ToDateTime(dateStr, "yyyy-MM-dd hh:mm");

It is good to specify the date kind, the code is:

var anotherParsedDate = DateTime.ParseExact(dateStr, "yyyy-MM-dd hh:mm", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);

More details on different parsing options

Python: import cx_Oracle ImportError: No module named cx_Oracle error is thown

To access Oracle from python you need (additionally) the cx_Oracle module. The module must be located either in the system python path or you have to set the PYTHONPATH appropriate.

Using lodash to compare jagged arrays (items existence without order)

By 'the same' I mean that there are is no item in array1 that is not contained in array2.

You could use flatten() and difference() for this, which works well if you don't care if there are items in array2 that aren't in array1. It sounds like you're asking is array1 a subset of array2?

var array1 = [['a', 'b'], ['b', 'c']];
var array2 = [['b', 'c'], ['a', 'b']];

function isSubset(source, target) {
    return !_.difference(_.flatten(source), _.flatten(target)).length;

isSubset(array1, array2); // ? true
isSubset(array1, array2); // ? false
isSubset(array2, array1); // ? true

jQuery SVG vs. Raphael

Oh Raphael has moved on significantly since June. There is a new charting library that can work with it and these are very eye catching. Raphael also supports full SVG path syntax and is incorporating really advanced path methods. Come see 1.2.8+ at my site (Shameless plug) and then bounce over to the Dmitry's site from there.

Popup window in winform c#

This is not so easy because basically popups are not supported in windows forms. Although windows forms is based on win32 and in win32 popup are supported. If you accept a few tricks, following code will set you going with a popup. You decide if you want to put it to good use :

class PopupWindow : Control
    private const int WM_ACTIVATE = 0x0006;
    private const int WM_MOUSEACTIVATE = 0x0021;

    private Control ownerControl;

    public PopupWindow(Control ownerControl)
        this.ownerControl = ownerControl;

    public Control OwnerControl
            return (this.ownerControl as Control);
            this.ownerControl = value;

    protected override CreateParams CreateParams
            CreateParams createParams = base.CreateParams;

            createParams.Style = WindowStyles.WS_POPUP |
                                 WindowStyles.WS_VISIBLE |
                                 WindowStyles.WS_CLIPSIBLINGS |
                                 WindowStyles.WS_CLIPCHILDREN |
                                 WindowStyles.WS_MAXIMIZEBOX |
            createParams.ExStyle = WindowsExtendedStyles.WS_EX_LEFT |
                                   WindowsExtendedStyles.WS_EX_LTRREADING |
                                   WindowsExtendedStyles.WS_EX_RIGHTSCROLLBAR | 

            createParams.Parent = (this.ownerControl != null) ? this.ownerControl.Handle : IntPtr.Zero;
            return createParams;

    [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
    public static extern IntPtr SetActiveWindow(HandleRef hWnd);

    protected override void WndProc(ref Message m)
        switch (m.Msg)
            case WM_ACTIVATE:
                    if ((int)m.WParam == 1)
                        //window is being activated
                        if (ownerControl != null)
                            SetActiveWindow(new HandleRef(this, ownerControl.FindForm().Handle));
            case WM_MOUSEACTIVATE:
                    m.Result = new IntPtr(MouseActivate.MA_NOACTIVATE);
        base.WndProc(ref m);

    protected override void OnPaint(PaintEventArgs e)
        e.Graphics.FillRectangle(SystemBrushes.Info, 0, 0, Width, Height);
        e.Graphics.DrawString((ownerControl as VerticalDateScrollBar).FirstVisibleDate.ToLongDateString(), this.Font, SystemBrushes.InfoText, 2, 2);

Experiment with it a bit, you have to play around with its position and its size. Use it wrong and nothing shows.

How to zoom in/out an UIImage object when user pinches screen?

Another easy way to do this is to place your UIImageView within a UIScrollView. As I describe here, you need to set the scroll view's contentSize to be the same as your UIImageView's size. Set your controller instance to be the delegate of the scroll view and implement the viewForZoomingInScrollView: and scrollViewDidEndZooming:withView:atScale: methods to allow for pinch-zooming and image panning. This is effectively what Ben's solution does, only in a slightly more lightweight manner, as you don't have the overhead of a full web view.

One issue you may run into is that the scaling within the scroll view comes in the form of transforms applied to the image. This may lead to blurriness at high zoom factors. For something that can be redrawn, you can follow my suggestions here to provide a crisper display after the pinch gesture is finished. hniels' solution could be used at that point to rescale your image.

What is an unhandled promise rejection?

When I instantiate a promise, I'm going to generate an asynchronous function. If the function goes well then I call the RESOLVE then the flow continues in the RESOLVE handler, in the THEN. If the function fails, then terminate the function by calling REJECT then the flow continues in the CATCH.

In NodeJs are deprecated the rejection handler. Your error is just a warning and I read it inside node.js github. I found this.

DEP0018: Unhandled promise rejections

Type: Runtime

Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

How to add a linked source folder in Android Studio?

You can add a source folder to the build script and then sync. Look for sourceSets in the documentation here:

I haven't found a good way of adding test source folders. I have manually added the source to the .iml file. Of course this means it will go away everytime the build script is synched.

Excel VBA: Copying multiple sheets into new workbook

This worked for me (I added an "if sheet visible" because in my case I wanted to skip hidden sheets)

   Sub Create_new_file()

Application.DisplayAlerts = False

Dim wb As Workbook
Dim wbNew As Workbook
Dim sh As Worksheet
Dim shNew As Worksheet
Dim pname, parea As String

Set wb = ThisWorkbook
Set wbNew = ActiveWorkbook

For Each sh In wb.Worksheets

    pname = sh.Name

    If sh.Visible = True Then

    sh.Copy After:=wbNew.Sheets(Sheets.Count)



    With Selection

        .PasteSpecial (xlValues)
        .PasteSpecial (xlFormats)
        .PasteSpecial (xlPasteColumnWidths)

    End With

    ActiveSheet.Name = pname

    End If



Application.DisplayAlerts = True

End Sub

How can I set selected option selected in vue.js 2?

<select v-model="challan.warehouse_id">
<option value="">Select Warehouse</option>
<option v-for="warehouse in warehouses" v-bind:value=""  >
   {{ }}

Here "challan.warehouse_id" come from "challan" object you get from:

editChallan: function() {
    let that = this;'/api/challan_list/get_challan_data', {
    challan_id: that.challan_id
 .then(function (response) {
    that.challan =;
 .catch(function (error) {
    that.errors = error;

How can I record a Video in my Android App.?

Check out this Sample Camera Preview code, CameraPreview. This would help you in devloping video recording code for video preview, create MediaRecorder object, and set video recording parameters.

tsc throws `TS2307: Cannot find module` for a local file

If use webstorm, press Ctrl+Alt+S and bring up the settings window. Languages&Frameworks>TypeScript, enable "use tsconfig.json" option.

Select multiple columns using Entity Framework

You can select to an anonymous type, for example

var dataset2 = 
    (from recordset in entities.processlists 
    where recordset.ProcessName == processname 
    select new
        serverName = recordset.ServerName,
        processId = recordset.ProcessID, 
        username = recordset.Username

Or you can create a new class that will represent your selection, for example

public class MyDataSet
    public string ServerName { get; set; }
    public string ProcessId { get; set; }
    public string Username { get; set; }

then you can for example do the following

 var dataset2 = 
    (from recordset in entities.processlists 
    where recordset.ProcessName == processname 
    select new MyDataSet
        ServerName = recordset.ServerName,
        ProcessId = recordset.ProcessID, 
        Username = recordset.Username

Python memory usage of numpy arrays

You can use array.nbytes for numpy arrays, for example:

>>> import numpy as np
>>> from sys import getsizeof
>>> a = [0] * 1024
>>> b = np.array(a)
>>> getsizeof(a)
>>> b.nbytes

Yahoo Finance All Currencies quote API Documentation

As NT3RP told us that:

... we (Yahoo!) don't have a Finance API. It appears some have reverse engineered an API that they use to pull Finance data, but they are breaking our Terms of Service...

So I just thought of sharing this site with you:
[update: site has moved to -]

This site says:

No access fees, no rate limits, no ugly XML - just free, hourly updated exchange rates in JSON format
[update: Free for personal use, a bargain for your business.]

I hope I've helped and this is of some use to you (and others too). : )

Return a 2d array from a function

This code returns a 2d array.

 #include <cstdio>

    // Returns a pointer to a newly created 2d array the array2D has size [height x width]

    int** create2DArray(unsigned height, unsigned width)
      int** array2D = 0;
      array2D = new int*[height];

      for (int h = 0; h < height; h++)
            array2D[h] = new int[width];

            for (int w = 0; w < width; w++)
                  // fill in some initial values
                  // (filling in zeros would be more logic, but this is just for the example)
                  array2D[h][w] = w + width * h;

      return array2D;

    int main()
      printf("Creating a 2D array2D\n");

      int height = 15;
      int width = 10;
      int** my2DArray = create2DArray(height, width);
      printf("Array sized [%i,%i] created.\n\n", height, width);

      // print contents of the array2D
      printf("Array contents: \n");

      for (int h = 0; h < height; h++)
            for (int w = 0; w < width; w++)
                  printf("%i,", my2DArray[h][w]);

          // important: clean up memory
          printf("Cleaning up memory...\n");
          for (  h = 0; h < height; h++)
            delete [] my2DArray[h];
          delete [] my2DArray;
          my2DArray = 0;

      return 0;

SQL LEFT-JOIN on 2 fields for MySQL

Let's try this way:

from a
left join b 
    on a.ip = b.ip 
        and a.port = b.port /*if you has to filter by columns from right table , then add this condition in ON clause*/
where a.somecolumn = somevalue /*if you have to filter by some column from left table, then add it to where condition*/

So, in where clause you can filter result set by column from right table only on this way:

where b.somecolumn <> (=) null

How to save DataFrame directly to Hive?

Saving to Hive is just a matter of using write() method of your SQLContext:



From Spark 2.2: use DataSet instead DataFrame.

Free ASP.Net and/or CSS Themes

I have used Open source Web Design in the past. They have quite a few css themes, don't know about ASP.Net

How to POST the data from a modal form of Bootstrap?

You CAN include a modal within a form. In the Bootstrap documentation it recommends the modal to be a "top level" element, but it still works within a form.

You create a form, and then the modal "save" button will be a button of type="submit" to submit the form from within the modal.

<form asp-action="AddUsersToRole" method="POST" class="mb-3">

    @await Html.PartialAsync("~/Views/Users/_SelectList.cshtml", Model.Users)

    <div class="modal fade" id="role-select-modal" tabindex="-1" role="dialog" aria-labelledby="role-select-modal" aria-hidden="true">
        <div class="modal-dialog" role="document">
            <div class="modal-content">
                <div class="modal-header">
                    <h5 class="modal-title" id="exampleModalLabel">Select a Role</h5>
                <div class="modal-body">
                <div class="modal-footer">
                    <button type="submit" class="btn btn-primary">Add Users to Role</button>
                    <button type="button" class="btn btn-secondary" data-dismiss="modal">Cancel</button>


You can post (or GET) your form data to any URL. By default it is the serving page URL, but you can change it by setting the form action. You do not have to use ajax.

Mozilla documentation on form action

Strange Jackson exception being thrown when serializing Hibernate object

You can add a Jackson mixin on Object.class to always ignore hibernate-related properties. If you are using Spring Boot put this in your Application class:

public Jackson2ObjectMapperBuilder jacksonBuilder() {
    Jackson2ObjectMapperBuilder b = new Jackson2ObjectMapperBuilder();
    b.mixIn(Object.class, IgnoreHibernatePropertiesInJackson.class);
    return b;

@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
private abstract class IgnoreHibernatePropertiesInJackson{ }

"Keep Me Logged In" - the best approach

Generate a hash, maybe with a secret only you know, then store it in your DB so it can be associated with the user. Should work quite well.

connecting to mysql server on another PC in LAN

In Ubuntu Follow these steps:

  1. Set bind-address at /etc/mysql/mysql.conf.d

Change bind-address = to bind-address = 192.24.805.50 # your IP

  1. Grant permission for the remote machine

    mysql>GRANT ALL PRIVILEGES ON . TO 'root'@'[remoteip]' IDENTIFIED BY 'anypassword' WITH GRANT OPTION;

  2. Then try connect from remote machine

    mysql -u root -h 192.24.805.50 -p

shuffling/permutating a DataFrame in pandas

A simple solution in pandas is to use the sample method independently on each column. Use apply to iterate over each column:

df = pd.DataFrame({'a':[1,2,3,4,5,6], 'b':[1,2,3,4,5,6]})

   a  b
0  1  1
1  2  2
2  3  3
3  4  4
4  5  5
5  6  6

df.apply(lambda x: x.sample(frac=1).values)

   a  b
0  4  2
1  1  6
2  6  5
3  5  3
4  2  4
5  3  1

You must use .value so that you return a numpy array and not a Series, or else the returned Series will align to the original DataFrame not changing a thing:

df.apply(lambda x: x.sample(frac=1))

   a  b
0  1  1
1  2  2
2  3  3
3  4  4
4  5  5
5  6  6

How to display request headers with command line curl

A command like the one below will show three sections: request headers, response headers and data (separated by CRLF). It avoids technical information and syntactical noise added by curl.

curl -vs 2>&1 | sed '/^* /d; /bytes data]$/d; s/> //; s/< //'

The command will produce the following output:

GET / HTTP/1.1
User-Agent: curl/7.54.0
Accept: */*

HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=UTF-8
Content-Length: 149
Accept-Ranges: bytes
Date: Wed, 16 Jan 2019 20:28:56 GMT
Via: 1.1 varnish
Connection: keep-alive
X-Served-By: cache-bma1622-BMA
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1547670537.588756,VS0,VE105
Vary: Fastly-SSL
X-DNS-Prefetch-Control: off
Set-Cookie: prov=e4b211f7-ae13-dad3-9720-167742a5dff8;; expires=Fri, 01-Jan-2055 00:00:00 GMT; path=/; HttpOnly

<head><title>Document Moved</title></head>
<body><h1>Object Moved</h1>This document may be found <a HREF="">here</a></body>


  • -vs - add headers (-v) but remove progress bar (-s)
  • 2>&1 - combine stdout and stderr into single stdout
  • sed - edit response produced by curl using the commands below
  • /^* /d - remove lines starting with '* ' (technical info)
  • /bytes data]$/d - remove lines ending with 'bytes data]' (technical info)
  • s/> // - remove '> ' prefix
  • s/< // - remove '< ' prefix

reading from stdin in c++

You have not defined the variable input_line.

Add this:

string input_line;

And add this include.

#include <string>

Here is the full example. I also removed the semi-colon after the while loop, and you should have getline inside the while to properly detect the end of the stream.

#include <iostream>
#include <string>

int main() {
    for (std::string line; std::getline(std::cin, line);) {
        std::cout << line << std::endl;
    return 0;

How to use hex() without 0x in Python?

You can simply write


to get the first two characters removed.

Dependency Walker reports IESHIMS.DLL and WER.DLL missing?

1· Do I need these DLL's?

It depends since Dependency Walker is a little bit out of date and may report the wrong dependency.

  1. Where can I get them?

most dlls can be found at

I believe they are supposed to located in C:\Windows\System32\Wer.dll and C:\Program Files\Internet Explorer\Ieshims.dll

For me leshims.dll can be placed at C:\Windows\System32\. Context: windows 7 64bit.

align text center with android

use this way


How do I schedule a task to run at periodic intervals?

Use timer.scheduleAtFixedRate

public void scheduleAtFixedRate(TimerTask task,
                                long delay,
                                long period)

Schedules the specified task for repeated fixed-rate execution, beginning after the specified delay. Subsequent executions take place at approximately regular intervals, separated by the specified period.
In fixed-rate execution, each execution is scheduled relative to the scheduled execution time of the initial execution. If an execution is delayed for any reason (such as garbage collection or other background activity), two or more executions will occur in rapid succession to "catch up." In the long run, the frequency of execution will be exactly the reciprocal of the specified period (assuming the system clock underlying Object.wait(long) is accurate).

Fixed-rate execution is appropriate for recurring activities that are sensitive to absolute time, such as ringing a chime every hour on the hour, or running scheduled maintenance every day at a particular time. It is also appropriate for recurring activities where the total time to perform a fixed number of executions is important, such as a countdown timer that ticks once every second for ten seconds. Finally, fixed-rate execution is appropriate for scheduling multiple repeating timer tasks that must remain synchronized with respect to one another.


  • task - task to be scheduled.
  • delay - delay in milliseconds before task is to be executed.
  • period - time in milliseconds between successive task executions.


  • IllegalArgumentException - if delay is negative, or delay + System.currentTimeMillis() is negative.
  • IllegalStateException - if task was already scheduled or cancelled, timer was cancelled, or timer thread terminated.

How to make a page redirect using JavaScript?


document.location.href = "" + document.getElementById('somefield');

That would get the value of some text field or hidden field, and add it to your site URL to get a new URL (href). You can modify this to suit your needs.

Why are only a few video games written in Java?

Game marketing is a commercial process; publishers want quantifiable low-risk returns on their investment. As a consequence, the focus is usually on technology gimmicks (with exceptions) that consumers will buy to produce reliable return - these tend to be superficial visual effects such as lens glare or higher resolution. These effects are reliable because they simply use increases in processing power - they exploit the hardware/Moore's law increases. this implies using C/C++ - java is usually too abstracted from the hardware to exploit these benefits.

Run a Command Prompt command from Desktop Shortcut

  1. Create new text file on desktop;

  2. Enter desired commands in text file;

  3. Rename extension of text file from ".txt" --> ".bat"

Is there are way to make a child DIV's width wider than the parent DIV using CSS?

Adding to Nils Kaspersson's solution, I am resolving for the width of the vertical scrollbar as well. I am using 16px as an example, which is subtracted from the view-port width. This will avoid the horizontal scrollbar from appearing.

width: calc(100vw - 16px);
left: calc(-1 * (((100vw - 16px) - 100%) / 2));

How to wait for async method to complete?

Actually I found this more helpful for functions that return IAsyncAction.

            var task = asyncFunction();
            while (task.Status == AsyncStatus.Completed) ;

javascript if number greater than number

You're comparing strings. JavaScript compares the ASCII code for each character of the string.

To see why you get false, look at the charCodes:


The comparison is false because, when comparing the strings, the character codes for 1 is not greater than that of 9.

The fix is to treat the strings as numbers. You can use a number of methods:

parseInt(string, radix)
parseInt("1300", 10);
> 1300 - notice the lack of quotes

> 1300

> 1300

Specifying trust store information in spring boot

I was also having the same issue with Spring Boot and embedded Tomcat.

From what I understand these properties only set the Tomcat configuration parameters. According to the Tomcat documentation this is only used for Client authentication (i.e. for two-way SSL) and not for verifying remote certificates:

truststoreFile - The trust store file to use to validate client certificates.

In order to configure the trust store for HttpClient it largely depends on the HttpClient implementation you use. For instance for RestTemplate by default Spring Boot uses a SimpleClientHttpRequestFactory based on standard J2SE classes like

I've come up with a solution based on the Apache HttpClient docs and these posts:

Basically this allows for a RestTemplate bean that only trusts certificates signed by the root CA in the configured truststore.

public class RestClientConfig {

    // e.g. Add to
    private Resource trustStore;

    private char[] trustStorePassword;

    private Integer maxPoolSize;

    public ClientHttpRequestFactory httpRequestFactory() {
        return new HttpComponentsClientHttpRequestFactory(httpClient());

    public HttpClient httpClient() {

        // Trust own CA and all child certs
        Registry<ConnectionSocketFactory> socketFactoryRegistry = null;
        try {
            SSLContext sslContext = SSLContexts

            // Since only our own certs are trusted, hostname verification is probably safe to bypass
            SSLConnectionSocketFactory sslSocketFactory = new SSLConnectionSocketFactory(sslContext,
                    new HostnameVerifier() {

                        public boolean verify(final String hostname,
                                final SSLSession session) {
                            return true;

            socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
                    .register("http", PlainConnectionSocketFactory.getSocketFactory())
                    .register("https", sslSocketFactory)

        } catch (Exception e) {
            //TODO: handle exceptions

        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
        // This client is for internal connections so only one route is expected
        return HttpClientBuilder.create()

    public RestTemplate restTemplate() {
        RestTemplate restTemplate = new RestTemplate();
        return restTemplate;

And then you can use this custom Rest client whenever you need to, e.g.:

private RestTemplate restTemplate;


This assumes your trying to connect to a Rest endpoint, but you can also use the above HttpClient bean for whatever you want.

SQL Server: Query fast, but slow from procedure

I was experiencing this problem. My query looked something like:

select a, b, c from sometable where date > '20140101'

My stored procedure was defined like:

create procedure my_procedure (@dtFrom date)
select a, b, c from sometable where date > @dtFrom

I changed the datatype to datetime and voila! Went from 30 minutes to 1 minute!

create procedure my_procedure (@dtFrom datetime)
select a, b, c from sometable where date > @dtFrom

How to mute an html5 video player using jQuery

$("video").prop('muted', true); //mute


$("video").prop('muted', false); //unmute

See all events here

(side note: use attr if in jQuery < 1.6)

Object reference not set to an instance of an object.

The correct way in .NET 4.0 is:

if (String.IsNullOrWhiteSpace(strSearch))

The String.IsNullOrWhiteSpace method used above is equivalent to:

if (strSearch == null || strSearch == String.Empty || strSearch.Trim().Length == 0) 
// String.Empty is the same as ""

Reference for IsNullOrWhiteSpace method

Indicates whether a specified string is Nothing, empty, or consists only of white-space characters.

In earlier versions, you could do something like this:

if (String.IsNullOrEmpty(strSearch) || strSearch.Trim().Length == 0)

The String.IsNullOrEmpty method used above is equivalent to:

if (strSearch == null || strSearch == String.Empty)

Which means you still need to check for your "IsWhiteSpace" case with the .Trim().Length == 0 as per the example.

Reference for IsNullOrEmpty method

Indicates whether the specified string is Nothing or an Empty string.


You need to ensure strSearch (or any variable for that matter) is not null before you dereference it using the dot character (.) - i.e. before you do strSearch.SomeMethod() or strSearch.SomeProperty you need to check that strSearch != null.

In your example you want to make sure your string has a value, which means you want to ensure the string:

  • Is not null
  • Is not the empty string (String.Empty / "")
  • Is not just whitespace

In the cases above, you must put the "Is it null?" case first, so it doesn't go on to check the other cases (and error) when the string is null.

Change div width live with jQuery

It is indeed possible to change a div elements' width in jQuery:

$("#div").css("width", "300px");

However, what you're describing can be better and more effectively achieved in CSS by setting a width as a percentage:

#div {
    width: 75%;
    /* You can also specify min/max widths */
    min-width: 300px;
    max-width: 960px;

This div will then always be 75% the width of the screen, unless the screen width means the div will be smaller than 300px, or bigger than 960px.

Automatically enter SSH password with script

# create a file that echo's out your password .. you may need to get crazy with escape chars or for extra credit put ASCII in your password...
echo "echo YerPasswordhere" > /tmp/1
chmod 777 /tmp/1

# sets some vars for ssh to play nice with something to do with GUI but here we are using it to pass creds.
export SSH_ASKPASS="/tmp/1"
setsid ssh [email protected] -p 22


Can I use tcpdump to get HTTP requests, response header and response body?

I would recommend using Wireshark, which has a "Follow TCP Stream" option that makes it very easy to see the full requests and responses for a particular TCP connection. If you would prefer to use the command line, you can try tcpflow, a tool dedicated to capturing and reconstructing the contents of TCP streams.

Other options would be using an HTTP debugging proxy, like Charles or Fiddler as EricLaw suggests. These have the advantage of having specific support for HTTP to make it easier to deal with various sorts of encodings, and other features like saving requests to replay them or editing requests.

You could also use a tool like Firebug (Firefox), Web Inspector (Safari, Chrome, and other WebKit-based browsers), or Opera Dragonfly, all of which provide some ability to view the request and response headers and bodies (though most of them don't allow you to see the exact byte stream, but instead how the browsers parsed the requests).

And finally, you can always construct requests by hand, using something like telnet, netcat, or socat to connect to port 80 and type the request in manually, or a tool like htty to help easily construct a request and inspect the response.

Convert HTML to NSAttributedString in iOS

Swift initializer extension on NSAttributedString

My inclination was to add this as an extension to NSAttributedString rather than String. I tried it as a static extension and an initializer. I prefer the initializer which is what I've included below.

Swift 4

internal convenience init?(html: String) {
    guard let data = String.Encoding.utf16, allowLossyConversion: false) else {
        return nil

    guard let attributedString = try?  NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue], documentAttributes: nil) else {
        return nil

    self.init(attributedString: attributedString)

Swift 3

extension NSAttributedString {

internal convenience init?(html: String) {
    guard let data = String.Encoding.utf16, allowLossyConversion: false) else {
        return nil

    guard let attributedString = try? NSMutableAttributedString(data: data, options: [NSAttributedString.DocumentReadingOptionKey.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil) else {
        return nil

    self.init(attributedString: attributedString)


let html = "<b>Hello World!</b>"
let attributedString = NSAttributedString(html: html)

Formatting a double to two decimal places

Since you are working in currency why not simply do this:

Console.Writeline("Earnings this week: {0:c}", answer);

This will format answer as currency, so on my machine (UK) it will come out as:

Earnings this week: £209.00

How to get the nth occurrence in a string?

Shorter way and I think easier, without creating unnecessary strings.

const findNthOccurence = (string, nth, char) => {
  let index = 0
  for (let i = 0; i < nth; i += 1) {
    if (index !== -1) index = string.indexOf(char, index + 1)
  return index

Pointers in C: when to use the ampersand and the asterisk?

Ok, looks like your post got editted...

double foo[4];
double *bar_1 = &foo[0];

See how you can use the & to get the address of the beginning of the array structure? The following

Foo_1(double *bar, int size){ return bar[size-1]; }
Foo_2(double bar[], int size){ return bar[size-1]; }

will do the same thing.

What's a .sh file?

sh files are unix (linux) shell executables files, they are the equivalent (but much more powerful) of bat files on windows.

So you need to run it from a linux console, just typing its name the same you do with bat files on windows.

How do I list the symbols in a .so file

You can use the nm -g tool from the binutils toolchain. However, their source is not always readily available. and I'm not actually even sure that this information can always be retrieved. Perhaps objcopy reveals further information.

/EDIT: The tool's name is of course nm. The flag -g is used to show only exported symbols.

How to implement static class member functions in *.cpp file?

Try this:


class CFoo
    static bool IsThisThingOn();


#include "header.hxx"
bool CFoo::IsThisThingOn() // note: no static keyword here
    return true;

Launch an app on OS X with command line

I wanted to have two separate instances of Chrome running, each using its own profile. I wanted to be able to start them from Spotlight, as is my habit for starting Mac apps. In other words, I needed two regular Mac applications, regChrome for normal browsing and altChrome to use the special profile, to be easily started by keying ?-space to bring up Spotlight, then 'reg' or 'alt', then Enter.

I suppose the brute-force way to accomplish the above goal would be to make two copies of the Google Chrome application bundle under the respective names. But that's ugly and complicates updating.

What I ended up with was two AppleScript applications containing two commands each. Here is the one for altChrome:

do shell script "cd /Applications/Google\\; rm app.icns; ln /Users/garbuck/local/chromeLaunchers/Chrome-swirl.icns app.icns"
do shell script "/Applications/Google\\\\ Chrome --user-data-dir=/Users/garbuck/altChrome >/dev/null 2>&1 &"

The second line starts Chrome with the alternate profile (the --user-data-dir parameter).

The first line is an unsuccessful attempt to give the two applications distinct icons. Initially, it appears to work fine. However, sooner or later, Chrome rereads its icon file and gets the one corresponding to whichever of the two apps was started last, resulting in two running applications with the same icon. But I haven't bothered to try to fix it — I keep the two browsers on separate desktops, and navigating between them hasn't been a problem.

Basic CSS - how to overlay a DIV with semi-transparent DIV on top

Here's a pure CSS solution, similar to DarkBee's answer, but without the need for an extra .wrapper div:

.dimmed {
  position: relative;

.dimmed:after {
  content: " ";
  z-index: 10;
  display: block;
  position: absolute;
  height: 100%;
  top: 0;
  left: 0;
  right: 0;
  background: rgba(0, 0, 0, 0.5);

I'm using rgba here, but of course you can use other transparency methods if you like.

Convert Variable Name to String?

What are you trying to achieve? There is absolutely no reason to ever do what you describe, and there is likely a much better solution to the problem you're trying to solve..

The most obvious alternative to what you request is a dictionary. For example:

>>> my_data = {'var': 'something'}
>>> my_data['something_else'] = 'something'
>>> print my_data.keys()
['var', 'something_else']
>>> print my_data['var']

Mostly as a.. challenge, I implemented your desired output. Do not use this code, please!

#!/usr/bin/env python2.6
class NewLocals:
    """Please don't ever use this code.."""
    def __init__(self, initial_locals):
        self.prev_locals = list(initial_locals.keys())

    def show_new(self, new_locals):
        output = ", ".join(list(set(new_locals) - set(self.prev_locals)))
        self.prev_locals = list(new_locals.keys())
        return output
# Set up
eww = None
eww = NewLocals(locals())

# "Working" requested code

var = {}

print eww.show_new(locals())  # Outputs: var

something_else = 3
print eww.show_new(locals()) # Outputs: something_else

# Further testing

another_variable = 4
and_a_final_one = 5

print eww.show_new(locals()) # Outputs: another_variable, and_a_final_one

Masking password input from the console : Java

A full example ?. Run this code : (NB: This example is best run in the console and not from within an IDE, since the System.console() method might return null in that case.)

public class Main {

    public void passwordExample() {        
        Console console = System.console();
        if (console == null) {
            System.out.println("Couldn't get Console instance");

        console.printf("Testing password%n");
        char[] passwordArray = console.readPassword("Enter your secret password: ");
        console.printf("Password entered was: %s%n", new String(passwordArray));


    public static void main(String[] args) {
        new Main().passwordExample();

Ruby: How to turn a hash into HTTP parameters?

If you are in the context of a Faraday request, you can also just pass the params hash as the second argument and faraday takes care of making proper param URL part out of it:

faraday_instance.get(url, params_hsh)

Server Error in '/' Application. ASP.NET

Looks like this is a very generic message from iis. in my case we enabled integrated security on web config but forgot to change IIS app pool identity. Things to check -

  • go to event viewer on your server and check exact message.
  • -make sure your app pool and web config using same security(E.g Windows,integrated)

Note: this may not help every time but this might be one of the reason for above error message.

How do I get the day month and year from a Windows cmd.exe script?

Extract Day, Month and Year

The highest voted function and the accepted one do NOT work locale-independently since the DATE command is subject to localization too. For example (the accepted one): In English you have YYYY for year and in Holland it is JJJJ. So this is a no-go. The following script takes the users' localization from the registry, which is locale-independent.

@echo off

::: Begin set date
setlocal EnableExtensions EnableDelayedExpansion

:: Determine short date format (independent from localization) from registry
for /f "skip=1 tokens=3-5 delims=- " %%L in ( '2^>nul reg query "HKCU\Control Panel\International" /v "sShortDate"' ) do ( 

    :: Since we can have multiple (short) date formats we only use the first char from the format in a new variable
    set "_L=%%L" && set "_L=!_L:~0,1!" && set "_M=%%M" && set "_M=!_M:~0,1!" && set "_N=%%N" && set "_N=!_N:~0,1!"

    :: Now assign the date values to the new vars
    for /f "tokens=2-4 delims=/-. " %%D in ( "%date%" ) do ( set "!_L!=%%D" && set "!_M!=%%E" && set "!_N!=%%F" )

:: Print the values as is
echo This is the original date string --^> %date%
echo These are the splitted values    --^> Day: %d%, Month:%m%, Year: %y%.


Extract only the Year

For a script I wrote I wanted only to extract the year (locale-independent) so I came up with this oneliner as I couldn't find any solution. It uses the 'DATE' var, multiple delimiters and checks for a number greater than 31. That then will be the current year. It's low on resources in contrast to some of the other solutions.

@echo off

setlocal EnableExtensions

for /f " tokens=2-4 delims=-./ " %%D in ( "%date%" ) do ( if %%D gtr 31 ( set "_YEAR=%%D" ) else ( if %%E gtr 31 ( set "_YEAR=%%E" ) else ( if %%F gtr 31 ( set "_YEAR=%%F" ) ) ) )

echo And the year is... %_YEAR%.


Is it ok to scrape data from Google results?

Google thrives on scraping websites of the if it was "so illegal" then even Google won't survive ..of course other answers mention ways of mitigating IP blocks by Google. One more way to explore avoiding captcha could be scraping at random times (dint try) ..Moreover, I have a feeling, that if we provide novelty or some significant processing of data then it sounds fine at least to me...if we are simply copying a website.. or hampering its business/brand in some way...then it is bad and should be avoided..on top of it all...if you are a startup then no one will fight you as there is no benefit.. but if your entire premise is on scraping even when you are funded then you should think of more sophisticated ways...alternative APIs..eventually..Also Google keeps releasing (or depricating) fields for its API so what you want to scrap now may be in roadmap of new Google API releases..

MySQL query finding values in a comma separated string

You can achieve this by following function.

Run following query to create function.

CREATE FUNCTION `TOTAL_OCCURANCE`(`commastring` TEXT, `findme`     VARCHAR(255)) RETURNS int(11)
-- SANI: First param is for comma separated string and 2nd for string to find.
return ROUND (   
        - LENGTH( REPLACE ( commastring, findme, "") ) 
    ) / LENGTH(findme)        

And call this function like this

msyql> select TOTAL_OCCURANCE('A,B,C,A,D,X,B,AB', 'A');

How to add a changed file to an older (not last) commit in Git

To "fix" an old commit with a small change, without changing the commit message of the old commit, where OLDCOMMIT is something like 091b73a:

git add <my fixed files>
git commit --fixup=OLDCOMMIT
git rebase --interactive --autosquash OLDCOMMIT^

You can also use git commit --squash=OLDCOMMIT to edit the old commit message during rebase.

See documentation for git commit and git rebase. As always, when rewriting git history, you should only fixup or squash commits you have not yet published to anyone else (including random internet users and build servers).

Detailed explanation

  • git commit --fixup=OLDCOMMIT copies the OLDCOMMIT commit message and automatically prefixes fixup! so it can be put in the correct order during interactive rebase. (--squash=OLDCOMMIT does the same but prefixes squash!.)
  • git rebase --interactive will bring up a text editor (which can be configured) to confirm (or edit) the rebase instruction sequence. There is info for rebase instruction changes in the file; just save and quit the editor (:wq in vim) to continue with the rebase.
  • --autosquash will automatically put any --fixup=OLDCOMMIT commits in the correct order. Note that --autosquash is only valid when the --interactive option is used.
  • The ^ in OLDCOMMIT^ means it's a reference to the commit just before OLDCOMMIT. (OLDCOMMIT^ is the first parent of OLDCOMMIT.)

Optional automation

The above steps are good for verification and/or modifying the rebase instruction sequence, but it's also possible to skip/automate the interactive rebase text editor by:

Python os.path.join() on a list

I stumbled over the situation where the list might be empty. In that case:

os.path.join('', *the_list_with_path_components)

Note the first argument, which will not alter the result.

VBA check if object is set

If obj Is Nothing Then
    ' need to initialize obj: '
    Set obj = ...
    ' obj already set / initialized. '
End If

Or, if you prefer it the other way around:

If Not obj Is Nothing Then
    ' obj already set / initialized. '
    ' need to initialize obj: '
    Set obj = ...
End If

Adding ASP.NET MVC5 Identity Authentication to an existing project

Configuring Identity to your existing project is not hard thing. You must install some NuGet package and do some small configuration.

First install these NuGet packages with Package Manager Console:

PM> Install-Package Microsoft.AspNet.Identity.Owin 
PM> Install-Package Microsoft.AspNet.Identity.EntityFramework
PM> Install-Package Microsoft.Owin.Host.SystemWeb 

Add a user class and with IdentityUser inheritance:

public class AppUser : IdentityUser
    //add your custom properties which have not included in IdentityUser before
    public string MyExtraProperty { get; set; }  

Do same thing for role:

public class AppRole : IdentityRole
    public AppRole() : base() { }
    public AppRole(string name) : base(name) { }
    // extra properties here 

Change your DbContext parent from DbContext to IdentityDbContext<AppUser> like this:

public class MyDbContext : IdentityDbContext<AppUser>
    // Other part of codes still same 
    // You don't need to add AppUser and AppRole 
    // since automatically added by inheriting form IdentityDbContext<AppUser>

If you use the same connection string and enabled migration, EF will create necessary tables for you.

Optionally, you could extend UserManager to add your desired configuration and customization:

public class AppUserManager : UserManager<AppUser>
    public AppUserManager(IUserStore<AppUser> store)
        : base(store)

    // this method is called by Owin therefore this is the best place to configure your User Manager
    public static AppUserManager Create(
        IdentityFactoryOptions<AppUserManager> options, IOwinContext context)
        var manager = new AppUserManager(
            new UserStore<AppUser>(context.Get<MyDbContext>()));

        // optionally configure your manager
        // ...

        return manager;

Since Identity is based on OWIN you need to configure OWIN too:

Add a class to App_Start folder (or anywhere else if you want). This class is used by OWIN. This will be your startup class.

namespace MyAppNamespace
    public class IdentityConfig
        public void Configuration(IAppBuilder app)
            app.CreatePerOwinContext(() => new MyDbContext());
            app.CreatePerOwinContext<RoleManager<AppRole>>((options, context) =>
                new RoleManager<AppRole>(
                    new RoleStore<AppRole>(context.Get<MyDbContext>())));

            app.UseCookieAuthentication(new CookieAuthenticationOptions
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
                LoginPath = new PathString("/Home/Login"),

Almost done just add this line of code to your web.config file so OWIN could find your startup class.

    <!-- other setting here -->
    <add key="owin:AppStartup" value="MyAppNamespace.IdentityConfig" />

Now in entire project you could use Identity just like any new project had already installed by VS. Consider login action for example

public ActionResult Login(LoginViewModel login)
    if (ModelState.IsValid)
        var userManager = HttpContext.GetOwinContext().GetUserManager<AppUserManager>();
        var authManager = HttpContext.GetOwinContext().Authentication;

        AppUser user = userManager.Find(login.UserName, login.Password);
        if (user != null)
            var ident = userManager.CreateIdentity(user, 
            //use the instance that has been created. 
                new AuthenticationProperties { IsPersistent = false }, ident);
            return Redirect(login.ReturnUrl ?? Url.Action("Index", "Home"));
    ModelState.AddModelError("", "Invalid username or password");
    return View(login);

You could make roles and add to your users:

public ActionResult CreateRole(string roleName)
    var roleManager=HttpContext.GetOwinContext().GetUserManager<RoleManager<AppRole>>();

    if (!roleManager.RoleExists(roleName))
        roleManager.Create(new AppRole(roleName));
    // rest of code

You could also add a role to a user, like this:

UserManager.AddToRole(UserManager.FindByName("username").Id, "roleName");

By using Authorize you could guard your actions or controllers:

public ActionResult MySecretAction() {}


[Authorize(Roles = "Admin")]]
public ActionResult MySecretAction() {}

You can also install additional packages and configure them to meet your requirement like Microsoft.Owin.Security.Facebook or whichever you want.

Note: Don't forget to add relevant namespaces to your files:

using Microsoft.AspNet.Identity;
using Microsoft.Owin.Security;
using Microsoft.AspNet.Identity.Owin;
using Microsoft.AspNet.Identity.EntityFramework;
using Microsoft.Owin;
using Microsoft.Owin.Security.Cookies;
using Owin;

You could also see my other answers like this and this for advanced use of Identity.

Spark - Error "A master URL must be set in your configuration" when submitting an app

var appName:String ="test"
val conf = new SparkConf().setAppName(appName).setMaster("local[*]").set("spark.executor.memory","1g");
val sc =  SparkContext.getOrCreate(conf)

Automating the InvokeRequired code pattern

Lee's approach can be simplified further

public static void InvokeIfRequired(this Control control, MethodInvoker action)
    // See Update 2 for edits Mike de Klerk suggests to insert here.

    if (control.InvokeRequired) {
    } else {

And can be called like this

richEditControl1.InvokeIfRequired(() =>
    // Do anything you want with the control here
    richEditControl1.RtfText = value;

There is no need to pass the control as parameter to the delegate. C# automatically creates a closure.


According to several other posters Control can be generalized as ISynchronizeInvoke:

public static void InvokeIfRequired(this ISynchronizeInvoke obj,
                                         MethodInvoker action)
    if (obj.InvokeRequired) {
        var args = new object[0];
        obj.Invoke(action, args);
    } else {

DonBoitnott pointed out that unlike Control the ISynchronizeInvoke interface requires an object array for the Invoke method as parameter list for the action.


Edits suggested by Mike de Klerk (see comment in 1st code snippet for insert point):

// When the form, thus the control, isn't visible yet, InvokeRequired  returns false,
// resulting still in a cross-thread exception.
while (!control.Visible)

See ToolmakerSteve's comment below for concerns about this suggestion.

Excel how to fill all selected blank cells with text

If all the cells are under one column, you could just filter the column and then select "(blank)" and then insert any value into the cells. But be careful, press "alt + 4" to make sure you are inserting value into the visible cells only.

Python: can't assign to literal

1, 2, 3 ,... are invalid identifiers in python because first of all they are integer objects and secondly in python a variable name can't start with a number.

>>> 1 = 12    #you can't assign to an integer
  File "<ipython-input-177-30a62b7248f1>", line 1
SyntaxError: can't assign to literal

>>> 1a = 12   #1a is an invalid variable name
  File "<ipython-input-176-f818ca46b7dc>", line 1
    1a = 12
SyntaxError: invalid syntax

Valid identifier definition:

identifier ::=  (letter|"_") (letter | digit | "_")*
letter     ::=  lowercase | uppercase
lowercase  ::=  "a"..."z"
uppercase  ::=  "A"..."Z"
digit      ::=  "0"..."9"

Make Iframe to fit 100% of container's remaining height

We use a JavaScript to solve this problem; here is the source.

var buffer = 20; //scroll bar buffer
var iframe = document.getElementById('ifm');

function pageY(elem) {
    return elem.offsetParent ? (elem.offsetTop + pageY(elem.offsetParent)) : elem.offsetTop;

function resizeIframe() {
    var height = document.documentElement.clientHeight;
    height -= pageY(document.getElementById('ifm'))+ buffer ;
    height = (height < 0) ? 0 : height;
    document.getElementById('ifm').style.height = height + 'px';

// .onload doesn't work with IE8 and older.
if (iframe.attachEvent) {
    iframe.attachEvent("onload", resizeIframe);
} else {

window.onresize = resizeIframe;

Note: ifm is the iframe ID

pageY() was created by John Resig (the author of jQuery)

Getting attributes of Enum's value

Adding my solution for Net Framework and NetCore.

I used this for my Net Framework implementation:

public static class EnumerationExtension
    public static string Description( this Enum value )
        // get attributes  
        var field = value.GetType().GetField( value.ToString() );
        var attributes = field.GetCustomAttributes( typeof( DescriptionAttribute ), false );

        // return description
        return attributes.Any() ? ( (DescriptionAttribute)attributes.ElementAt( 0 ) ).Description : "Description Not Found";

This doesn't work for NetCore so I modified it to do this:

public static class EnumerationExtension
    public static string Description( this Enum value )
        // get attributes  
        var field = value.GetType().GetField( value.ToString() );
        var attributes = field.GetCustomAttributes( false );

        // Description is in a hidden Attribute class called DisplayAttribute
        // Not to be confused with DisplayNameAttribute
        dynamic displayAttribute = null;

        if (attributes.Any())
            displayAttribute = attributes.ElementAt( 0 );

        // return description
        return displayAttribute?.Description ?? "Description Not Found";

Enumeration Example:

public enum ExportTypes
    [Display( Name = "csv", Description = "text/csv" )]
    CSV = 0

Sample Usage for either static added:

var myDescription = myEnum.Description();

What is the difference between 'typedef' and 'using' in C++11?

I know the original poster has a great answer, but for anyone stumbling on this thread like I have there's an important note from the proposal that I think adds something of value to the discussion here, particularly to concerns in the comments about if the typedef keyword is going to be marked as deprecated in the future, or removed for being redundant/old:

It has been suggested to (re)use the keyword typedef ... to introduce template aliases:

template<class T>
  typedef std::vector<T, MyAllocator<T> > Vec;

That notation has the advantage of using a keyword already known to introduce a type alias. However, it also displays several disavantages [sic] among which the confusion of using a keyword known to introduce an alias for a type-name in a context where the alias does not designate a type, but a template; Vec is not an alias for a type, and should not be taken for a typedef-name. The name Vec is a name for the family std::vector<•, MyAllocator<•> > – where the bullet is a placeholder for a type-name.Consequently we do not propose the “typedef” syntax.On the other hand the sentence

template<class T>
  using Vec = std::vector<T, MyAllocator<T> >;

can be read/interpreted as: from now on, I’ll be using Vec<T> as a synonym for std::vector<T, MyAllocator<T> >. With that reading, the new syntax for aliasing seems reasonably logical.

To me, this implies continued support for the typedef keyword in C++ because it can still make code more readable and understandable.

Updating the using keyword was specifically for templates, and (as was pointed out in the accepted answer) when you are working with non-templates using and typedef are mechanically identical, so the choice is totally up to the programmer on the grounds of readability and communication of intent.

async for loop in node.js

I've reduced your code sample to the following lines to make it easier to understand the explanation of the concept.

var results = [];
var config = JSON.parse(queries);
for (var key in config) {
    var query = config[key].query;
    search(query, function(result) {
res.writeHead( ... );

The problem with the previous code is that the search function is asynchronous, so when the loop has ended, none of the callback functions have been called. Consequently, the list of results is empty.

To fix the problem, you have to put the code after the loop in the callback function.

    search(query, function(result) {
        // Put res.writeHead( ... ) and res.end(results) here

However, since the callback function is called multiple times (once for every iteration), you need to somehow know that all callbacks have been called. To do that, you need to count the number of callbacks, and check whether the number is equal to the number of asynchronous function calls.

To get a list of all keys, use Object.keys. Then, to iterate through this list, I use .forEach (you can also use for (var i = 0, key = keys[i]; i < keys.length; ++i) { .. }, but that could give problems, see JavaScript closure inside loops – simple practical example).

Here's a complete example:

var results = [];
var config = JSON.parse(queries);
var onComplete = function() {
    res.writeHead( ... );
var keys = Object.keys(config);
var tasksToGo = keys.length;
if (tasksToGo === 0) {
} else {
    // There is at least one element, so the callback will be called.
    keys.forEach(function(key) {
        var query = config[key].query;
        search(query, function(result) {
            if (--tasksToGo === 0) {
                // No tasks left, good to go

Note: The asynchronous code in the previous example are executed in parallel. If the functions need to be called in a specific order, then you can use recursion to get the desired effect:

var results = [];
var config = JSON.parse(queries);
var keys = Object.keys(config);
(function next(index) {
    if (index === keys.length) { // No items left
        res.writeHead( ... );
    var key = keys[index];
    var query = config[key].query;
    search(query, function(result) {
        next(index + 1);

What I've shown are the concepts, you could use one of the many (third-party) NodeJS modules in your implementation, such as async.

Pandas: rolling mean by time interval

I found that user2689410 code broke when I tried with window='1M' as the delta on business month threw this error:

AttributeError: 'MonthEnd' object has no attribute 'delta'

I added the option to pass directly a relative time delta, so you can do similar things for user defined periods.

Thanks for the pointers, here's my attempt - hope it's of use.

def rolling_mean(data, window, min_periods=1, center=False):
""" Function that computes a rolling mean

data : DataFrame or Series
       If a DataFrame is passed, the rolling_mean is computed for all columns.
window : int, string, Timedelta or Relativedelta
         int - number of observations used for calculating the statistic,
               as defined by the function pd.rolling_mean()
         string - must be a frequency string, e.g. '90S'. This is
                  internally converted into a DateOffset object, and then
                  Timedelta representing the window size.
         Timedelta / Relativedelta - Can directly pass a timedeltas.
min_periods : int
              Minimum number of observations in window required to have a value.
center : bool
         Point around which to 'center' the slicing.

Series or DataFrame, if more than one column
def f(x, time_increment):
    """Function to apply that actually computes the rolling mean
    :param x:
    if not center:
        # adding a microsecond because when slicing with labels start
        # and endpoint are inclusive
        start_date = x - time_increment + timedelta(0, 0, 1)
        end_date = x
        start_date = x - time_increment/2 + timedelta(0, 0, 1)
        end_date = x + time_increment/2
    # Select the date index from the
    dslice = col[start_date:end_date]

    if dslice.size < min_periods:
        return np.nan
        return dslice.mean()

data = DataFrame(data.copy())
dfout = DataFrame()
if isinstance(window, int):
    dfout = pd.rolling_mean(data, window, min_periods=min_periods, center=center)

elif isinstance(window, basestring):
    time_delta = pd.datetools.to_offset(window).delta
    idx = Series(data.index.to_pydatetime(), index=data.index)
    for colname, col in data.iteritems():
        result = idx.apply(lambda x: f(x, time_delta)) = colname
        dfout = dfout.join(result, how='outer')

elif isinstance(window, (timedelta, relativedelta)):
    time_delta = window
    idx = Series(data.index.to_pydatetime(), index=data.index)
    for colname, col in data.iteritems():
        result = idx.apply(lambda x: f(x, time_delta)) = colname
        dfout = dfout.join(result, how='outer')

if dfout.columns.size == 1:
    dfout = dfout.ix[:, 0]
return dfout

And the example with a 3 day time window to calculate the mean:

from pandas import Series, DataFrame
import pandas as pd
from datetime import datetime, timedelta
import numpy as np
from dateutil.relativedelta import relativedelta

idx = [datetime(2011, 2, 7, 0, 0),
           datetime(2011, 2, 7, 0, 1),
           datetime(2011, 2, 8, 0, 1, 30),
           datetime(2011, 2, 9, 0, 2),
           datetime(2011, 2, 10, 0, 4),
           datetime(2011, 2, 11, 0, 5),
           datetime(2011, 2, 12, 0, 5, 10),
           datetime(2011, 2, 12, 0, 6),
           datetime(2011, 2, 13, 0, 8),
           datetime(2011, 2, 14, 0, 9)]
idx = pd.Index(idx)
vals = np.arange(len(idx)).astype(float)
s = Series(vals, index=idx)
# Now try by passing the 3 days as a relative time delta directly.
rm = rolling_mean(s, window=relativedelta(days=3))
>>> rm
2011-02-07 00:00:00    0.0
2011-02-07 00:01:00    0.5
2011-02-08 00:01:30    1.0
2011-02-09 00:02:00    1.5
2011-02-10 00:04:00    3.0
2011-02-11 00:05:00    4.0
2011-02-12 00:05:10    5.0
2011-02-12 00:06:00    5.5
2011-02-13 00:08:00    6.5
2011-02-14 00:09:00    7.5
Name: 0, dtype: float64

jQuery get the location of an element relative to window

Try the bounding box. It's simple:

var leftPos  = $("#element")[0].getBoundingClientRect().left   + $(window)['scrollLeft']();
var rightPos = $("#element")[0].getBoundingClientRect().right  + $(window)['scrollLeft']();
var topPos   = $("#element")[0].getBoundingClientRect().top    + $(window)['scrollTop']();
var bottomPos= $("#element")[0].getBoundingClientRect().bottom + $(window)['scrollTop']();

How to change color of Android ListView separator line?

For a single color line use:

list.setDivider(new ColorDrawable(0x99F10529));   //0xAARRGGBB

It's important that DividerHeight is set after the divider, else you won't get anything.

How to submit form on change of dropdown list?

other than using this.form.submit() you also submiting by id or name. example i have form like this : <form action="" name="PostName" id="IdName">

  1. By Name : <select onchange="PostName.submit()">

  2. By Id : <select onchange="IdName.submit()">

How to make a TextBox accept only alphabetic characters?

Try This

            private void tbCustomerName_KeyPress(object sender, KeyPressEventArgs e)
        e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back||e.KeyChar==(char)Keys.Space);

It Allows White Spaces Too

How to edit an Android app?

First you have to download file x-plore and installed it.. After that open it and find the thoes you want to edit.. After that just rename the file Xyz.apk to After that open that file and you can see some folders.. then just go and edit the app..

Multiple IF statements between number ranges

It's a little tricky because of the nested IFs but here is my answer (confirmed in Google Spreadsheets):

=IF(AND(A2>=0,    A2<500),  "Less than 500", 
 IF(AND(A2>=500,  A2<1000), "Between 500 and 1000", 
 IF(AND(A2>=1000, A2<1500), "Between 1000 and 1500", 
 IF(AND(A2>=1500, A2<2000), "Between 1500 and 2000", "Undefined"))))

POST unchecked HTML checkboxes

The problem with checkboxes is that if they are not checked then they are not posted with your form. If you check a checkbox and post a form you will get the value of the checkbox in the $_POST variable which you can use to process a form, if it's unchecked no value will be added to the $_POST variable.

In PHP you would normally get around this problem by doing an isset() check on your checkbox element. If the element you are expecting isn't set in the $_POST variable then we know that the checkbox is not checked and the value can be false.

     $checkboxValue = false;
} else {
     $checkboxValue = $_POST['checkbox1'];

But if you have created a dynamic form then you won't always know the name attribute of your checkboxes, if you don't know the name of the checkbox then you can't use the isset function to check if this has been sent with the $_POST variable.

How to completely uninstall Visual Studio 2010?

The only real clean way to uninstall VS (Visual Studio, whatever version it is) is to completely reinstall the whole OS. If you don't, more compatibility problems might surface.

Permanent solution

Starting from scratch (clean install, VS never installed on the OS), the best way to avoid all those problems is to install and run VS from a VM (virtual machine) as stated by Default in the comments above. This way, and as long as Microsoft doesn't do anything to improve its whole platform to be more user-friendly, switching from a version to another will be quick and easy and the main partition of the HDD (or SSD in my case) won't be filed with all the garbage that VS leaves behind.

Of course, the disadvantage is speed. The program will be slower in pretty much every way. But honestly, who uses VS for its speed? Even on the latest enthusiast-platforms, it takes ages to install. Even if VS might start up faster on a high-end SSD, it's just slow.

whitespaces in the path of windows filepath

path = r"C:\Users\mememe\Google Drive\Programs\Python\file.csv"

Closing the path in r"string" also solved this problem very well.

CSS: background-color only inside the margin

I needed something similar, and came up with using the :before (or :after) pseudoclasses:

#mydiv {
   background-color: #fbb;
   margin-top: 100px;
   position: relative;
#mydiv:before {
   content: "";
   background-color: #bfb;
   top: -100px;
   height: 100px;
   width: 100%;
   position: absolute;


Scroll to element on click in Angular 4

You can do this by using jquery :

ts code :

    scrollTOElement = (element, offsetParam?, speedParam?) => {
    const toElement = $(element);
    const focusElement = $(element);
    const offset = offsetParam * 1 || 200;
    const speed = speedParam * 1 || 500;
    $('html, body').animate({
      scrollTop: toElement.offset().top + offset
    }, speed);
    if (focusElement) {

html code :

<button (click)="scrollTOElement('#elementTo',500,3000)">Scroll</button>

Apply this on elements you want to scroll :

<div id="elementTo">some content</div>

Here is a stackblitz sample.

How do you append to a file?

Python has many variations off of the main three modes, these three modes are:

'w'   write text
'r'   read text
'a'   append text

So to append to a file it's as easy as:

f = open('filename.txt', 'a') 
f.write('whatever you want to write here (in append mode) here.')

Then there are the modes that just make your code fewer lines:

'r+'  read + write text
'w+'  read + write text
'a+'  append + read text

Finally, there are the modes of reading/writing in binary format:

'rb'  read binary
'wb'  write binary
'ab'  append binary
'rb+' read + write binary
'wb+' read + write binary
'ab+' append + read binary

How to make a HTTP PUT request?

using(var client = new System.Net.WebClient()) {

What's a decent SFTP command-line client for windows?

This little application does the job for me. I could not find another CLI based client that would access my IIS based TLS/SSL secured ftp site:

Provide password to ssh command inside bash script, Without the usage of public keys and Expect

First of all: Don't put secrets in clear text unless you know why it is a safe thing to do (i.e. you have assessed what damage can be done by an attacker knowing the secret).

If you are ok with putting secrets in your script, you could ship an ssh key with it and execute in an ssh-agent shell:

#!/usr/bin/env ssh-agent /usr/bin/env bash
cat << EOF > ${KEYFILE}
ssh-add ${KEYFILE}

# do your ssh things here...

# Remove the key file.
rm -f ${KEYFILE}

A benefit of using ssh keys is that you can easily use forced commands to limit what the keyholder can do on the server.

A more secure approach would be to let the script run ssh-keygen -f ~/.ssh/my-script-key to create a private key specific for this purpose, but then you would also need a routine for adding the public key to the server.

FlutterError: Unable to load asset

You should consider the indentation for assets


    - images/pizza1.png
    - images/pizza0.png

More details:


[2 whitespaces or 1 tab]assets:
[4 whitespaces or 2 tabs]- images/pizza1.png
[4 whitespaces or 2 tabs]- images/pizza0.png

Hash Map in Python

Here is the implementation of the Hash Map using python For the simplicity hash map is of a fixed size 16. This can be changed easily. Rehashing is out of scope of this code.

class Node:
    def __init__(self, key, value):
        self.key = key
        self.value = value = None

class HashMap:
    def __init__(self): = [None for _ in range(16)]
    def get(self, key):
        index = hash(key) & 15
        if[index] is None:
            return None
        n =[index]
        while True:
            if n.key == key:
                return n.value
                    n =
                    return None
    def put(self, key, value):
        nd = Node(key, value)
        index = hash(key) & 15
        n =[index]
        if n is None:
  [index] = nd
            if n.key == key:
                n.value = value
                    if n.key == key:
                        n.value = value
                        n =
       = nd

hm = HashMap()
hm.put("1", "sachin")
hm.put("2", "sehwag")
hm.put("3", "ganguly")
hm.put("4", "srinath")
hm.put("5", "kumble")
hm.put("6", "dhoni")
hm.put("7", "kohli")
hm.put("8", "pandya")
hm.put("9", "rohit")
hm.put("10", "dhawan")
hm.put("11", "shastri")
hm.put("12", "manjarekar")
hm.put("13", "gupta")
hm.put("14", "agarkar")
hm.put("15", "nehra")
hm.put("16", "gawaskar")
hm.put("17", "vengsarkar")



How can I position my jQuery dialog to center?

Could not get IE9 to center the dialog.

Fixed it by adding this to the css:

.ui-dialog {

Percent doesn't matter. Any small number worked.

How to use the onClick event for Hyperlink using C# code?

The onclick attribute on your anchor tag is going to call a client-side function. (This is what you would use if you wanted to call a javascript function when the link is clicked.)

What you want is a server-side control, like the LinkButton:

<asp:LinkButton ID="lnkTutorial" runat="server" Text="Tutorial" OnClick="displayTutorial_Click"/>

This has an OnClick attribute that will call the method in your code behind.

Looking further into your code, it looks like you're just trying to open a different tutorial based on access level of the user. You don't need an event handler for this at all. A far better approach would be to just set the end point of your LinkButton control in the code behind.

protected void Page_Load(object sender, EventArgs e)
    userinfo = (UserInfo)Session["UserInfo"];

    if (userinfo.user == "Admin")
        lnkTutorial.PostBackUrl = "help/AdminTutorial.html";
        lnkTutorial.PostBackUrl = "help/UserTutorial.html";

Really, it would be best to check that you actually have a user first.

protected void Page_Load(object sender, EventArgs e)
    if (Session["UserInfo"] != null && ((UserInfo)Session["UserInfo"]).user == "Admin")
        lnkTutorial.PostBackUrl = "help/AdminTutorial.html";
        lnkTutorial.PostBackUrl = "help/UserTutorial.html";

Using IF ELSE statement based on Count to execute different Insert statements

As long as you need to find it based on Count just more than 0, it is better to use EXISTS like this:

IF EXISTS (SELECT 1 FROM INCIDENTS  WHERE [Some Column] = 'Target Data')
    -- TRUE Procedure
    -- FALSE Procedure

How to set a maximum execution time for a mysql query?

If you're using the mysql native driver (common since php 5.3), and the mysqli extension, you can accomplish this with an asynchronous query:


// Here's an example query that will take a long time to execute.
$sql = "
    select *
    from information_schema.tables t1
    join information_schema.tables t2
    join information_schema.tables t3
    join information_schema.tables t4
    join information_schema.tables t5
    join information_schema.tables t6
    join information_schema.tables t7
    join information_schema.tables t8

$mysqli = mysqli_connect('localhost', 'root', '');
$mysqli->query($sql, MYSQLI_ASYNC | MYSQLI_USE_RESULT);
$links = $errors = $reject = [];
$links[] = $mysqli;

// wait up to 1.5 seconds
$seconds = 1;
$microseconds = 500000;

$timeStart = microtime(true);

if (mysqli_poll($links, $errors, $reject, $seconds, $microseconds) > 0) {
    echo "query finished executing. now we start fetching the data rows over the network...\n";
    $result = $mysqli->reap_async_query();
    if ($result) {
        while ($row = $result->fetch_row()) {
            // print_r($row);
            if (microtime(true) - $timeStart > 1.5) {
                // we exceeded our time limit in the middle of fetching our result set.
                echo "timed out while fetching results\n";
} else {
    echo "timed out while waiting for query to execute\n";

The flags I'm giving to mysqli_query accomplish important things. It tells the client driver to enable asynchronous mode, while forces us to use more verbose code, but lets us use a timeout(and also issue concurrent queries if you want!). The other flag tells the client not to buffer the entire result set into memory.

By default, php configures its mysql client libraries to fetch the entire result set of your query into memory before it lets your php code start accessing rows in the result. This can take a long time to transfer a large result. We disable it, otherwise we risk that we might time out while waiting for the buffering to complete.

Note that there's two places where we need to check for exceeding a time limit:

  • The actual query execution
  • while fetching the results(data)

You can accomplish similar in the PDO and regular mysql extension. They don't support asynchronous queries, so you can't set a timeout on the query execution time. However, they do support unbuffered result sets, and so you can at least implement a timeout on the fetching of the data.

For many queries, mysql is able to start streaming the results to you almost immediately, and so unbuffered queries alone will allow you to somewhat effectively implement timeouts on certain queries. For example, a

select * from tbl_with_1billion_rows

can start streaming rows right away, but,

select sum(foo) from tbl_with_1billion_rows

needs to process the entire table before it can start returning the first row to you. This latter case is where the timeout on an asynchronous query will save you. It will also save you from plain old deadlocks and other stuff.

ps - I didn't include any timeout logic on the connection itself.

Extract filename and extension in Bash

If you also want to allow empty extensions, this is the shortest I could come up with:

echo 'hello.txt' | sed -r 's/.+\.(.+)|.*/\1/' # EXTENSION
echo 'hello.txt' | sed -r 's/(.+)\..+|(.*)/\1\2/' # FILENAME

1st line explained: It matches PATH.EXT or ANYTHING and replaces it with EXT. If ANYTHING was matched, the ext group is not captured.

T-SQL split string

The easiest way to do this is by using XML format.

1. Converting string to rows without table


DECLARE @String varchar(100) = 'String1,String2,String3'
-- To change ',' to any other delimeter, just change ',' to your desired one
DECLARE @Delimiter CHAR = ','    

SELECT LTRIM(RTRIM(Split.a.value('.', 'VARCHAR(100)'))) 'Value' 
     SELECT CAST ('<M>' + REPLACE(@String, @Delimiter, '</M><M>') + '</M>' AS XML) AS Data            
) AS A 
CROSS APPLY Data.nodes ('/M') AS Split(a)


 | Value   |
 | String1 |
 | String2 |
 | String3 |

2. Converting to rows from a table which have an ID for each CSV row


 | Id  |           Value          |
 |  1  |  String1,String2,String3 |
 |  2  |  String4,String5,String6 |     


-- To change ',' to any other delimeter, just change ',' before '</M><M>' to your desired one
DECLARE @Delimiter CHAR = ','

SELECT ID,LTRIM(RTRIM(Split.a.value('.', 'VARCHAR(100)'))) 'Value' 
     SELECT ID,CAST ('<M>' + REPLACE(VALUE, @Delimiter, '</M><M>') + '</M>' AS XML) AS Data            
) AS A 
CROSS APPLY Data.nodes ('/M') AS Split(a)


 | Id  |  Value   |
 |  1  |  String1 |
 |  1  |  String2 |  
 |  1  |  String3 |
 |  2  |  String4 |  
 |  2  |  String5 |
 |  2  |  String6 |     

Cannot inline bytecode built with JVM target 1.8 into bytecode that is being built with JVM target 1.6

In my case this code did'n work until I move apply plugin: 'kotlin-android' from bottom to top.

apply plugin: ''
apply plugin: 'kotlin-android'

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8

    kotlinOptions {
        jvmTarget = "1.8"

pandas python how to count the number of records or rows in a dataframe

Simply, row_num = df.shape[0] # gives number of rows, here's the example:

import pandas as pd
import numpy as np

In [322]: df = pd.DataFrame(np.random.randn(5,2), columns=["col_1", "col_2"])

In [323]: df
      col_1     col_2
0 -0.894268  1.309041
1 -0.120667 -0.241292
2  0.076168 -1.071099
3  1.387217  0.622877
4 -0.488452  0.317882

In [324]: df.shape
Out[324]: (5, 2)

In [325]: df.shape[0]   ## Gives no. of rows/records
Out[325]: 5

In [326]: df.shape[1]   ## Gives no. of columns
Out[326]: 2

How to change SmartGit's licensing option after 30 days of commercial use on ubuntu?

My own solution on Linux (under ~/.config/smartgit/19.1) is to comment or remove line listx from preferences.yml file and reopen program.

Deleting the all folders will make you reconfigure everything (useless).

How do I get current scope dom-element in AngularJS controller?

In controller:

function innerItem($scope, $element){
    var jQueryInnerItem = $($element); 

Change Name of Import in Java, or import two classes with the same name

As the other answers already stated, Java does not provide this feature.

Implementation of this feature has been requested multiple times, e.g. as JDK-4194542: class name aliasing or JDK-4214789: Extend import to allow renaming of imported type.

From the comments:

This is not an unreasonable request, though hardly essential. The occasional use of fully qualified names is not an undue burden (unless the library really reuses the same simple names right and left, which is bad style).

In any event, it doesn't pass the bar of price/performance for a language change.

So I guess we will not see this feature in Java anytime soon :-P

How to set an image as a background for Frame in Swing GUI of java?

The Background Panel entry shows a couple of different ways depending on your requirements.

How do I force make/GCC to show me the commands?

Library makefiles, which are generated by autotools (the ./configure you have to issue) often have a verbose option, so basically, using make VERBOSE=1 or make V=1 should give you the full commands.

But this depends on how the makefile was generated.

The -d option might help, but it will give you an extremely long output.