Programs & Examples On #Camelcasing

Camel case is a language-independent naming convention in which an identifier name will start with a lowercase letter and each additional word within the name will start uppercase, such as customerName, printInvoice, etc.

Elegant Python function to convert CamelCase to snake_case?

Using regexes may be the shortest, but this solution is way more readable:

def to_snake_case(s):
    snake = "".join(["_"+c.lower() if c.isupper() else c for c in s])
    return snake[1:] if snake.startswith("_") else snake

Converting any string into camel case

following @Scott's readable approach, a little bit of fine tuning

// convert any string to camelCase
var toCamelCase = function(str) {
  return str.toLowerCase()
    .replace( /['"]/g, '' )
    .replace( /\W+/g, ' ' )
    .replace( / (.)/g, function($1) { return $1.toUpperCase(); })
    .replace( / /g, '' );

How can I return camelCase JSON serialized by JSON.NET from ASP.NET MVC controller methods?

or, simply put:

    new JsonSerializerSettings 
        ContractResolver = new CamelCasePropertyNamesContractResolver() 

For instance:

return new ContentResult
    ContentType = "application/json",
    Content = JsonConvert.SerializeObject(new { content = result, rows = dto }, new JsonSerializerSettings { ContractResolver = new CamelCasePropertyNamesContractResolver() }),
    ContentEncoding = Encoding.UTF8

Convert a String to Modified Camel Case in Java or Title Case as is otherwise called

From commons-lang3

org.apache.commons.lang3.text.WordUtils.capitalizeFully(String str)

JSON Naming Convention (snake_case, camelCase or PascalCase)

Notably for me on NodeJS, if I'm working with databases and my field names are underscore separated, I also use them in the struct keys.

This is because db fields have a lot of acronyms/abbreviations so something like appSNSInterfaceRRTest looks a bit messy but app_sns_interface_rr_test is nicer.

In Javascript variables are all camelCase and class names (constructors) are ProperCase, so you'd see something like

var devTask = {
        task_id: 120,
        store_id: 2118,
        task_name: 'generalLedger'


generalLedgerTask = new GeneralLedgerTask( devTask );

And of course in JSON keys/strings are wrapped in double quotes, but then you just use the JSON.stringify and pass in JS objects, so don't need to worry about that.

I struggled with this a bit until I found this happy medium between JSON and JS naming conventions.

How to compare two dates to find time difference in SQL Server 2005, date manipulation

I think you need the time gap between job_start & job_end.

Try this...

select SUBSTRING(CONVERT(VARCHAR(20),(job_end - job_start),120),12,8) from tableA

I ended up with this.


How to refresh materialized view in oracle

EXECUTE dbms_mview.refresh('view name','cf');

Empty responseText from XMLHttpRequest

The browser is preventing you from cross-site scripting.

If the url is outside of your domain, then you need to do this on the server side or move it into your domain.

Search of table names

Adding on to @[RichardTheKiwi]'s answer.

Whenever I search for a list of tables, in general I want to select from all of them or delete them. Below is a script that generates those scripts for you.

The generated select script also adds a tableName column so you know what table you're looking at:

select 'select ''' + name + ''' as TableName, * from ' + name as SelectTable,
'delete from ' + name as DeleteTable
from sys.tables
where name like '%xxxx%'
and is_ms_shipped = 0; 

Manually highlight selected text in Notepad++

To highlight a block of code in Notepad++, please do the following steps

  1. Select the required text.
  2. Right click to display the context menu
  3. Choose Style token and select any of the five choices available ( styles from Using 1st style to using 5th style). Each is of different colors.If you want yellow color choose using 3rd style.

If you want to create your own style you can use Style Configurator under Settings menu.

How do I make a Mac Terminal pop-up/alert? Applescript?

Use this command to trigger the notification center notification from the terminal.

osascript -e 'display notification "Lorem ipsum dolor sit amet" with title "Title"'

Add legend to ggplot2 line plot

I tend to find that if I'm specifying individual colours in multiple geom's, I'm doing it wrong. Here's how I would plot your data:

##Subset the necessary columns
dd_sub = datos[,c(20, 2,3,5)]
##Then rearrange your data frame
dd = melt(dd_sub, id=c("fecha"))

All that's left is a simple ggplot command:

ggplot(dd) + geom_line(aes(x=fecha, y=value, colour=variable)) +

Example plot

enter image description here

How to serialize object to CSV file?

You can use gererics to work for any class

public class FileUtils<T> {
public String createReport(String filePath, List<T> t) {
    if (t.isEmpty()) {
        return null;

    List<String> reportData = new ArrayList<String>();

    addDataToReport(t.get(0), reportData, 0);

    for (T k : t) {
        addDataToReport(k, reportData, 1);
    return !dumpReport(filePath, reportData) ? null : filePath;

public static Boolean dumpReport(String filePath, List<String> lines) {
    Boolean isFileCreated = false;

    String[] dirs = filePath.split(File.separator);
    String baseDir = "";
    for (int i = 0; i < dirs.length - 1; i++) {
        baseDir += " " + dirs[i];
    baseDir = baseDir.replace(" ", "/");
    File base = new File(baseDir);

    File file = new File(filePath);
    try {
        if (!file.exists())
    } catch (Exception e) {
        return isFileCreated;

    try (BufferedWriter writer = new BufferedWriter(
            new OutputStreamWriter(new FileOutputStream(file), System.getProperty("file.encoding")))) {
        for (String line : lines) {
            writer.write(line + System.lineSeparator());
    } catch (IOException e) {
        return false;
    return true;

void addDataToReport(T t, List<String> reportData, int index) {
    String[] jsonObjectAsArray = new Gson().toJson(t).replace("{", "").replace("}", "").split(",\"");
    StringBuilder row = new StringBuilder();

    for (int i = 0; i < jsonObjectAsArray.length; i++) {
        String str = jsonObjectAsArray[i];
        str = str.replaceFirst(":", "_").split("_")[index];

        if (i == 0) {
            if (str != null) {
                row.append(str.replace("\"", ""));
            } else {
        } else {
            if (str != null) {
                row.append(", " + str.replace("\"", ""));
            } else {
                row.append(", N/A");

Android - running a method periodically using postDelayed() call

I think you could experiment with different activity flags, as it sounds like multiple instances.

"singleTop" "singleTask" "singleInstance"

Are the ones I would try, they can be defined inside the manifest.

String replacement in Objective-C

NSString objects are immutable (they can't be changed), but there is a mutable subclass, NSMutableString, that gives you several methods for replacing characters within a string. It's probably your best bet.

Double.TryParse or Convert.ToDouble - which is faster and safer?

I have always preferred using the TryParse() methods because it is going to spit back success or failure to convert without having to worry about exceptions.

Adding a legend to PyPlot in Matplotlib in the simplest manner possible

Here's an example to help you out ...

fig = plt.figure(figsize=(10,5))
ax = fig.add_subplot(111)
ax.set_title('ADR vs Rating (CS:GO)')
plt.plot(data[:,0], m*data[:,0] + b,color='red',label='Our Fitting 

enter image description here

document.getElementById('btnid').disabled is not working in firefox and chrome

There are always weird issues with browser support of getElementById, try using the following instead:

// document.getElementsBySelector are part of the prototype.js library available at

function disbtn(e) { 
    if ( someCondition == true ) {
        document.getElementsBySelector("#btn1")[0].setAttribute("disabled", "disabled");
    } else {

Alternatively, embrace jQuery where you could simply do this:

function disbtn(e) { 
    if ( someCondition == true ) {
        $("#btn1").attr("disabled", "disabled");
    } else {

How to add elements of a string array to a string array list?

You already have built-in method for that: -

List<String> species = Arrays.asList(speciesArr);

NOTE: - You should use List<String> species not ArrayList<String> species.

Arrays.asList returns a different ArrayList -> java.util.Arrays.ArrayList which cannot be typecasted to java.util.ArrayList.

Then you would have to use addAll method, which is not so good. So just use List<String>

NOTE: - The list returned by Arrays.asList is a fixed size list. If you want to add something to the list, you would need to create another list, and use addAll to add elements to it. So, then you would better go with the 2nd way as below: -

    String[] arr = new String[1];
    arr[0] = "rohit";
    List<String> newList = Arrays.asList(arr);

    // Will throw `UnsupportedOperationException
    // newList.add("jain"); // Can't do this.

    ArrayList<String> updatableList = new ArrayList<String>();


    updatableList.add("jain"); // OK this is fine. 

    System.out.println(newList);       // Prints [rohit]
    System.out.println(updatableList); //Prints [rohit, jain]

Convert base64 string to image

In the server, do something like this:


String data = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAPAAAADwCAYAAAA+VemSAAAgAEl...=='


String base64Image = data.split(",")[1];
byte[] imageBytes = javax.xml.bind.DatatypeConverter.parseBase64Binary(base64Image);

Then you can do whatever you like with the bytes like:

BufferedImage img = ByteArrayInputStream(imageBytes));

Accessing localhost (xampp) from another computer over LAN network - how to?

First Go To Network and Sharing center of your windows machine.and Just follow some steps to get your IPv4 address. Just See The Image Illustration

Put the IPv4 adress on another computer browser. example,http//


  • Turn Of Your Windows Firewall (if does not work,otherwise its optional)

Importing PNG files into Numpy?

I like the build-in pathlib libary because of quick options like directory= Path.cwd() Together with opencv it's quite easy to read pngs to numpy arrays. In this example you can even check the prefix of the image.

from pathlib import Path
import cv2
prefix = "p00"
suffix = ".png"
directory= Path.cwd()
file_names= [ for subp in directory.rglob('*') if  (prefix in & (suffix == subp.suffix)]

all_frames= []
for file_name in file_names:
    file_path = str(directory / file_name)
print(all_frames[0] [1][1])


['p000.png', 'p001.png', 'p002.png', 'p003.png', 'p004.png', 'p005.png', 'p006.png', 'p007.png', 'p008.png', 'p009.png']
<class 'numpy.ndarray'>
[255 255 255]

Difference between thread's context class loader and normal classloader

Each class will use its own classloader to load other classes. So if ClassA.class references ClassB.class then ClassB needs to be on the classpath of the classloader of ClassA, or its parents.

The thread context classloader is the current classloader for the current thread. An object can be created from a class in ClassLoaderC and then passed to a thread owned by ClassLoaderD. In this case the object needs to use Thread.currentThread().getContextClassLoader() directly if it wants to load resources that are not available on its own classloader.

What are some good Python ORM solutions?

SQLAlchemy's declarative extension, which is becoming standard in 0.5, provides an all in one interface very much like that of Django or Storm. It also integrates seamlessly with classes/tables configured using the datamapper style:

Base = declarative_base()

class Foo(Base):
    __tablename__ = 'foos'
    id = Column(Integer, primary_key=True)

class Thing(Base):
    __tablename__ = 'things'

    id = Column(Integer, primary_key=True)
    name = Column(Unicode)
    description = Column(Unicode)
    foo_id = Column(Integer, ForeignKey(''))
    foo = relation(Foo)

engine = create_engine('sqlite://')

Base.metadata.create_all(engine)  # issues DDL to create tables

session = sessionmaker(bind=engine)()

foo = Foo()
thing = Thing(name='thing1', description='some thing') = foo  # also adds Thing to session

Authenticate Jenkins CI for Github private repository

I had a similar problem with gitlab. It turns out I had restricted the users that are allowed to login via ssh. This won't affect github users, but in case people end up here for gitlab (and the like) issues, ensure you add git to the AllowUsers setting in /etc/ssh/sshd_config:

# Authentication:
LoginGraceTime 120
PermitRootLogin no
StrictModes yes
AllowUsers batman git

Sonar properties files

Do the build job on Jenkins first without Sonar configured. Then add Sonar, and run a build job again. Should fix the problem

Oracle SQL, concatenate multiple columns + add text

select 'i like' || type_column || ' with' ect....

scrollTop jquery, scrolling to div with id?

try this:

$('html, body').animate({scrollTop:$('#xxx').position().top}, 'slow');

JavaScript by reference vs. by value

Javascript always passes by value. However, if you pass an object to a function, the "value" is really a reference to that object, so the function can modify that object's properties but not cause the variable outside the function to point to some other object.

An example:

function changeParam(x, y, z) {
  x = 3;
  y = "new string";
  z["key2"] = "new";
  z["key3"] = "newer";

  z = {"new" : "object"};

var a = 1,
    b = "something",
    c = {"key1" : "whatever", "key2" : "original value"};

changeParam(a, b, c);

// at this point a is still 1
// b is still "something"
// c still points to the same object but its properties have been updated
// so it is now {"key1" : "whatever", "key2" : "new", "key3" : "newer"}
// c definitely doesn't point to the new object created as the last line
// of the function with z = ...

How to convert an Image to base64 string in java?

this did it for me. you can vary the options for the output format to Base64.Default whatsoever.

// encode base64 from image
ByteArrayOutputStream baos = new ByteArrayOutputStream();
imageBitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] b = baos.toByteArray();
encodedString = Base64.encodeToString(b, Base64.URL_SAFE | Base64.NO_WRAP);

Submitting the value of a disabled input field

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

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

How to execute a Windows command on a remote PC?

If you are in a domain environment, you can also use:

winrs -r:PCNAME cmd

This will open a remote command shell.

How to unpublish an app in Google Play Developer Console

To unpublish your app on the Google Play store:

  1. Go to, and log in to your Google Play account.
  2. Click on the application you want to delete.
  3. Click on the Store Presence menu, and click the “Pricing and Distribution” item.
  4. Click Unpublish

CSS3 equivalent to jQuery slideUp and slideDown?

I changed your solution, so that it works in all modern browsers:

css snippet:

-webkit-transition: height 1s ease-in-out;
-moz-transition: height 1s ease-in-out;
-ms-transition: height 1s ease-in-out;
-o-transition: height 1s ease-in-out;
transition: height 1s ease-in-out;

js snippet:

    var clone = $('#this').clone()

    var newHeight = $(".slideClone").height();
    $('#this').css('height',newHeight + 'px');

here's the full example

PHP DateTime __construct() Failed to parse time string (xxxxxxxx) at position x

Use the createFromFormat method:

$start_date = DateTime::createFromFormat("U", $dbResult->db_timestamp);


I now recommend the use of Carbon

How to invoke the super constructor in Python?

Short Answer

super(DerivedClass, self).__init__()

Long Answer

What does super() do?

It takes specified class name, finds its base classes (Python allows multiple inheritance) and looks for the method (__init__ in this case) in each of them from left to right. As soon as it finds method available, it will call it and end the search.

How do I call init of all base classes?

Above works if you have only one base class. But Python does allow multiple inheritance and you might want to make sure all base classes are initialized properly. To do that, you should have each base class call init:

class Base1:
  def __init__():
    super(Base1, self).__init__()

class Base2:
  def __init__():
    super(Base2, self).__init__()

class Derived(Base1, Base2):
  def __init__():
    super(Derived, self).__init__()

What if I forget to call init for super?

The constructor (__new__) gets invoked in a chain (like in C++ and Java). Once the instance is created, only that instance's initialiser (__init__) is called, without any implicit chain to its superclass.

How to fix "namespace x already contains a definition for x" error? Happened after converting to VS2010

I had this problem. It was due to me renaming a folder in the App_Code directory and releasing to my iis site folder. The original named folder was still present in my target directory - hence duplicate - (I don't do a full delete of target before copying) Anyway removing the old folder fixed this.

Disable Input fields in reactive form

Providing disabled property as true inside FormControl surely disables the input field.{
  FirstName:[{value:'first name', disabled:true}],
  LastValue:['last name,[Validators.required]]

The above example will disable the FirstName input field.

But real problem arises when you try to access disabled field value through form like this console.log(this.form.value.FirstName); and it shows as undefined instead of printing field's actual value. So, to access disabled field's value, one must use getRawValue() method provided by Reactive Forms. i.e. console.log(this.form.getRawValue().FirstName); would print the actual value of form field and not undefined.

How to get temporary folder for current user



How to show particular image as thumbnail while implementing share on Facebook?

From Facebook's spec, use a code like this:

<meta property="og:image" content="" />

Source: Facebook Share

Resource from src/main/resources not found after building with maven

Resources from src/main/resources will be put onto the root of the classpath, so you'll need to get the resource as:

new BufferedReader(new InputStreamReader(getClass().getResourceAsStream("/config.txt")));

You can verify by looking at the JAR/WAR file produced by maven as you'll find config.txt in the root of your archive.

Checkbox value true/false

If I understand the question, you want to change the value of the checkbox depending if it is checked or not.

Here is one solution:

$("#checkbox1").on('change', function() {_x000D_
  if ($(this).is(':checked')) {_x000D_
    $(this).attr('value', 'true');_x000D_
  } else {_x000D_
    $(this).attr('value', 'false');_x000D_
<script src=""></script>_x000D_
<input type="checkbox" name="acceptRules" class="inline checkbox" id="checkbox1" value="false">_x000D_
<div id="checkbox-value"></div>

Concat scripts in order with Gulp

With gulp-useref you can concatenate every script declared in your index file, in the order in which you declare it.

var $ = require('gulp-load-plugins')();
gulp.task('jsbuild', function () {
  var assets = $.useref.assets({searchPath: '{.tmp,app}'});
  return gulp.src('app/**/*.html')
    .pipe($.if('*.js', $.uglify({preserveComments: 'some'})))
    .pipe($.size({title: 'html'}));

And in the HTML you have to declare the name of the build file you want to generate, like this:

<!-- build:js js/main.min.js -->
    <script src="js/vendor/vendor.js"></script>
    <script src="js/modules/test.js"></script>
    <script src="js/main.js"></script>

In your build directory you will have the reference to main.min.js which will contain vendor.js, test.js, and main.js

Check if object exists in JavaScript

I used to just do a if(maybeObject) as the null check in my javascripts.

    alert("GOT HERE");

So only if maybeObject - is an object, the alert would be shown. I have an example in my site.

How to read a .xlsx file using the pandas Library in iPython?

DataFrame's read_excel method is like read_csv method:

dfs = pd.read_excel(xlsx_file, sheetname="sheet1")

Help on function read_excel in module

read_excel(io, sheetname=0, header=0, skiprows=None, skip_footer=0, index_col=None, names=None, parse_cols=None, parse_dates=False, date_parser=None, na_values=None, thousands=None, convert_float=True, has_index_names=None, converters=None, true_values=None, false_values=None, engine=None, squeeze=False, **kwds)
    Read an Excel table into a pandas DataFrame

    io : string, path object (pathlib.Path or py._path.local.LocalPath),
        file-like object, pandas ExcelFile, or xlrd workbook.
        The string could be a URL. Valid URL schemes include http, ftp, s3,
        and file. For file URLs, a host is expected. For instance, a local
        file could be file://localhost/path/to/workbook.xlsx
    sheetname : string, int, mixed list of strings/ints, or None, default 0

        Strings are used for sheet names, Integers are used in zero-indexed
        sheet positions.

        Lists of strings/integers are used to request multiple sheets.

        Specify None to get all sheets.

        str|int -> DataFrame is returned.
        list|None -> Dict of DataFrames is returned, with keys representing

        Available Cases

        * Defaults to 0 -> 1st sheet as a DataFrame
        * 1 -> 2nd sheet as a DataFrame
        * "Sheet1" -> 1st sheet as a DataFrame
        * [0,1,"Sheet5"] -> 1st, 2nd & 5th sheet as a dictionary of DataFrames
        * None -> All sheets as a dictionary of DataFrames

    header : int, list of ints, default 0
        Row (0-indexed) to use for the column labels of the parsed
        DataFrame. If a list of integers is passed those row positions will
        be combined into a ``MultiIndex``
    skiprows : list-like
        Rows to skip at the beginning (0-indexed)
    skip_footer : int, default 0
        Rows at the end to skip (0-indexed)
    index_col : int, list of ints, default None
        Column (0-indexed) to use as the row labels of the DataFrame.
        Pass None if there is no such column.  If a list is passed,
        those columns will be combined into a ``MultiIndex``
    names : array-like, default None
        List of column names to use. If file contains no header row,
        then you should explicitly pass header=None
    converters : dict, default None
        Dict of functions for converting values in certain columns. Keys can
        either be integers or column labels, values are functions that take one
        input argument, the Excel cell content, and return the transformed
    true_values : list, default None
        Values to consider as True

        .. versionadded:: 0.19.0

    false_values : list, default None
        Values to consider as False

        .. versionadded:: 0.19.0

    parse_cols : int or list, default None
        * If None then parse all columns,
        * If int then indicates last column to be parsed
        * If list of ints then indicates list of column numbers to be parsed
        * If string then indicates comma separated list of column names and
          column ranges (e.g. "A:E" or "A,C,E:F")
    squeeze : boolean, default False
        If the parsed data only contains one column then return a Series
    na_values : scalar, str, list-like, or dict, default None
        Additional strings to recognize as NA/NaN. If dict passed, specific
        per-column NA values. By default the following values are interpreted
        as NaN: '', '#N/A', '#N/A N/A', '#NA', '-1.#IND', '-1.#QNAN', '-NaN', '-nan',
    '1.#IND', '1.#QNAN', 'N/A', 'NA', 'NULL', 'NaN', 'nan'.
    thousands : str, default None
        Thousands separator for parsing string columns to numeric.  Note that
        this parameter is only necessary for columns stored as TEXT in Excel,
        any numeric columns will automatically be parsed, regardless of display
    keep_default_na : bool, default True
        If na_values are specified and keep_default_na is False the default NaN
        values are overridden, otherwise they're appended to.
    verbose : boolean, default False
        Indicate number of NA values placed in non-numeric columns
    engine: string, default None
        If io is not a buffer or path, this must be set to identify io.
        Acceptable values are None or xlrd
    convert_float : boolean, default True
        convert integral floats to int (i.e., 1.0 --> 1). If False, all numeric
        data will be read in as floats: Excel stores all numbers as floats
    has_index_names : boolean, default None
        DEPRECATED: for version 0.17+ index names will be automatically
        inferred based on index_col.  To read Excel output from 0.16.2 and
        prior that had saved index names, use True.

    parsed : DataFrame or Dict of DataFrames
        DataFrame from the passed in Excel file.  See notes in sheetname
        argument for more information on when a Dict of Dataframes is returned.

How to convert rdd object to dataframe in spark

Assuming your RDD[row] is called rdd, you can use:

val sqlContext = new SQLContext(sc) 
import sqlContext.implicits._

Install pip in docker

While T. Arboreus's answer might fix the issues with resolving '', I think the last error you're getting says that it doesn't know about the packages php5-mcrypt and python-pip. Nevertheless, the reduced Dockerfile of you with just these two packages worked for me (using Debian 8.4 and Docker 1.11.0), but I'm not quite sure if that could be the case because my host system is different than yours.

FROM ubuntu:14.04

# Install dependencies
RUN apt-get update && apt-get install -y \
    php5-mcrypt \

However, according to this answer you should think about installing the python3-pip package instead of the python-pip package when using Python 3.x.

Furthermore, to make the php5-mcrypt package installation working, you might want to add the universe repository like it's shown right here. I had trouble with the add-apt-repository command missing in the Ubuntu Docker image so I installed the package software-properties-common at first to make the command available.

Splitting up the statements and putting apt-get update and apt-get install into one RUN command is also recommended here.

Oh and by the way, you actually don't need the -y flag at apt-get update because there is nothing that has to be confirmed automatically.


FROM ubuntu:14.04

# Install dependencies
RUN apt-get update && apt-get install -y \
RUN add-apt-repository universe
RUN apt-get update && apt-get install -y \
    apache2 \
    curl \
    git \
    libapache2-mod-php5 \
    php5 \
    php5-mcrypt \
    php5-mysql \
    python3.4 \

Remark: The used versions (e.g. of Ubuntu) might be outdated in the future.

How can I view all historical changes to a file in SVN

If you want to see whole history of a file with code changes :

svn log --diff [path_to_file] > log.txt

Delete with "Join" in Oracle sql Query

Based on the answer I linked to in my comment above, this should work:

delete from
select pf.* From PRODUCTFILTERS pf 
And pf.rowid in 
     Select rowid from PRODUCTFILTERS 
     And PRODUCTS.NAME= 'Mark'


delete from PRODUCTFILTERS where rowid in
select pf.rowid From PRODUCTFILTERS pf 
And pf.rowid in 
     And PRODUCTS.NAME= 'Mark'

Android Google Maps API V2 Zoom to Current Location

This is working Current Location with zoom for Google Map V2

 double lat= location.getLatitude();
 double lng = location.getLongitude();
 LatLng ll = new LatLng(lat, lng);
 googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(ll, 20));

Warning "Do not Access Superglobal $_POST Array Directly" on Netbeans 7.4 for PHP

filter_input(INPUT_POST, 'var_name') instead of $_POST['var_name']
filter_input_array(INPUT_POST) instead of $_POST

How do I convert the date from one format to another date object in another format without using any deprecated classes?

Use SimpleDateFormat#format:

DateFormat originalFormat = new SimpleDateFormat("MMMM dd, yyyy", Locale.ENGLISH);
DateFormat targetFormat = new SimpleDateFormat("yyyyMMdd");
Date date = originalFormat.parse("August 21, 2012");
String formattedDate = targetFormat.format(date);  // 20120821

Also note that parse takes a String, not a Date object, which is already parsed.

Vue is not defined

Sometimes the problem may be if you import that like this:

const Vue = window.vue;

this may overwrite the original Vue reference.

Send json post using php

You can use CURL for this purpose see the example code:

$url = "your url";    
$content = json_encode("your data to be sent");

$curl = curl_init($url);
curl_setopt($curl, CURLOPT_HEADER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HTTPHEADER,
        array("Content-type: application/json"));
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, $content);

$json_response = curl_exec($curl);

$status = curl_getinfo($curl, CURLINFO_HTTP_CODE);

if ( $status != 201 ) {
    die("Error: call to URL $url failed with status $status, response $json_response, curl_error " . curl_error($curl) . ", curl_errno " . curl_errno($curl));


$response = json_decode($json_response, true);

PHP Warning: Division by zero

If a variable is not set then it is NULL and if you try to divide something by null you will get a divides by zero error

addEventListener in Internet Explorer


I wrote a snippet that emulate the EventListener interface and the ie8 one, is callable even on plain objects:


this is a way for emulate addEventListener or attachEvent on browsers that don't support one of those
hope will help

(function (w,d) {  // 
        nc  = "", nu    = "", nr    = "", t,
        a   = "addEventListener",
        n   = a in w,
        c   = (nc = "Event")+(n?(nc+= "", "Listener") : (nc+="Listener","") ),
        u   = n?(nu = "attach", "add"):(nu = "add","attach"),
        r   = n?(nr = "detach","remove"):(nr = "remove","detach")
 * the evtf function, when invoked, return "attach" or "detach" "Event" functions if we are on a new browser, otherwise add "add" or "remove" "EventListener"
    function evtf(whoe){return function(evnt,func,capt){return this[whoe]((n?((t = evnt.split("on"))[1] || t[0]) : ("on"+evnt)),func, (!n && capt? (whoe.indexOf("detach") < 0 ? this.setCapture() : this.removeCapture() ) : capt  ))}}
    w[nu + nc] = Element.prototype[nu + nc] = document[nu + nc] = evtf(u+c) // (add | attach)Event[Listener]
    w[nr + nc] = Element.prototype[nr + nc] = document[nr + nc] = evtf(r+c) // (remove | detach)Event[Listener]

})(window, document)

How to show all of columns name on pandas dataframe?

To get all column name you can iterate over the data_all2.columns.

columns = data_all2.columns
for col in columns:
    print col

You will get all column names. Or you can store all column names to another list variable and then print list.

Download image from the site in .NET/C#

        private static void DownloadRemoteImageFile(string uri, string fileName)
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            if ((response.StatusCode == HttpStatusCode.OK ||
                response.StatusCode == HttpStatusCode.Moved ||
                response.StatusCode == HttpStatusCode.Redirect) &&
                response.ContentType.StartsWith("image", StringComparison.OrdinalIgnoreCase)) 
                using (Stream inputStream = response.GetResponseStream())
                using (Stream outputStream = File.OpenWrite(fileName))
                    byte[] buffer = new byte[4096];
                    int bytesRead;
                        bytesRead = inputStream.Read(buffer, 0, buffer.Length);
                        outputStream.Write(buffer, 0, bytesRead);
                    } while (bytesRead != 0);

Formula to convert date to number

If you change the format of the cells to General then this will show the date value of a cell as behind the scenes Excel saves a date as the number of days since 01/01/1900

Screenprint 1

Screenprint 2

If your date is text and you need to convert it then DATEVALUE will do this:

Datevalue function

Looking for simple Java in-memory cache

Try @Cacheable from jcabi-aspects. With a single annotation you make the entire method result cacheable in memory:

public class Resource {
  @Cacheable(lifetime = 5, unit = TimeUnit.SECONDS)
  public String load(URL url) {
    return url.openConnection().getContent();

Also, read this article:

Apache POI Excel - how to configure columns to be expanded?

If you know the count of your columns (f.e. it's equal to a collection list). You can simply use this one liner to adjust all columns of one sheet (if you use at least java 8):

IntStream.range(0, columnCount).forEach((columnIndex) -> sheet.autoSizeColumn(columnIndex));

Powershell Error "The term 'Get-SPWeb' is not recognized as the name of a cmdlet, function..."

Run this script from SharePoint 2010 Management Shell as Administrator.

How to install trusted CA certificate on Android device?

There is a MUCH easier solution to this than posted here, or in related threads. If you are using a webview (as I am), you can achieve this by executing a JAVASCRIPT function within it. If you are not using a webview, you might want to create a hidden one for this purpose. Here's a function that works in just about any browser (or webview) to kickoff ca installation (generally through the shared os cert repository, including on a Droid). It uses a nice trick with iFrames. Just pass the url to a .crt file to this function:

function installTrustedRootCert( rootCertUrl ){
    id = "rootCertInstaller";
    iframe = document.getElementById( id );
    if( iframe != null ) document.body.removeChild( iframe );
    iframe = document.createElement( "iframe" ); = id; = "none";
    document.body.appendChild( iframe );
    iframe.src = rootCertUrl;


The iframe trick works on Droids with API 19 and up, but older versions of the webview won't work like this. The general idea still works though - just download/open the file with a webview and then let the os take over. This may be an easier and more universal solution (in the actual java now):

 public static void installTrustedRootCert( final String certAddress ){
     WebView certWebView = new WebView( instance_ );
     certWebView.loadUrl( certAddress );

Note that instance_ is a reference to the Activity. This works perfectly if you know the url to the cert. In my case, however, I resolve that dynamically with the server side software. I had to add a fair amount of additional code to intercept a redirection url and call this in a manner which did not cause a crash based on a threading complication, but I won't add all that confusion here...

How to break out of nested loops?

Use this wise advice from LLVM team:

"Turn Predicate Loops into Predicate Functions"


How do you reverse a string in place in JavaScript?

You could can try:

const reverse = str => Array.from(str.normalize('NFC')).reverse().join('');

It's not a perfect solution, but it helps deal with characters consisting of multiple code-points. As pointed out, there are issues with maintaining composite and surrogate pair ordering in strings such as 'foo bar mañana man~ana'. Here is a surrogate pair, and the last n~ is a composite pair consisting of two Unicode characters to make up one grapheme.

In order to reverse each character, you can use the .reverse() method which is part of the Array prototype. As .reverse() can only be used on an array, the first thing to do is turn the string into an array of characters. Typically, .split('') is used for this task, however, this splits up surrogate pairs (as already shown in previous answers):

>> ''.split('')
>> `["?", "?"]`

Instead, if you invoke the String.prototype's Symbol.iterator method then you'll be able to retain your surrogate pairs within your array:

>> [...'']
>> [""]

The next thing to handle is any composite characters within the string. Characters which consist of two code points (which are not surrogate pairs) will still be split when iterated on:

>> [...'o¨']   
>> ["o", "¨"]

The above separates the base character and the diaresis, which is not desired behaviour. To deal with this, you can use a string method introduced in ES6 known as String.prototype.normalize(). This method can compose the multiple code points into its composed canonical form by using "NFC" as an argument. This is done by replacing multiple code points with single code points where possible. This allows graphemes consisting of two code points to be represented with one code point.

>> [...'o¨'.normalize('NFC')]   
>> ["ö"]

As this produces one character, it can then be reversed safely when amongst others. Putting both the spread syntax and normalization together, you can successfully reverse strings of characters such as:

const reverse = str => Array.from(str.normalize('NFC')).reverse().join('');

console.log(reverse('foo  bar mañana man~ana'));
console.log(reverse('This  emoji is happy'));

There are a few cases where the above will fail. For instance, the character ?? (heavy black heart ??) consists of two code points. The first being the heart and the latter being the variation selector-16 (U+FE0F) which is used to define a glyph variant for the preceding character. Other characters can also produce similar issues like this.

Another thing to look out for is ZWJ (Zero-width joiner) characters, which you can find in some scripts, including emoji. For example the emoji ?? comprises of the Man, Woman and Boy emoji, each separated by a ZWJ. The above reverse() method will not account for this either.

One way to fix this is to use Intl.Segmenter, which is currently a stage 3 proposal. However, there is a polyfill available for it if you wish to use it.

Here is how the reverse() method may look if you use Intl.Segmenter:

const reverse = str => {
  const segmenter = new Intl.Segmenter("en", {granularity: 'grapheme'});
  const segitr = segmenter.segment(str);
  const segarr = Array.from(segitr, ({segment}) => segment).reverse();
  return segarr.join('');

console.log(reverse('foo  bar mañana man~ana')); // anan~am anañam rab  oof
console.log(reverse('This  emoji is happy')); // yppah si ijome  sihT
console.log(reverse('Text surrogate pair  composite pair mo¨o varient selector ?? & ZWJ ??')); // ?? JWZ & ?? rotceles tneirav oo¨m riap etisopmoc  riap etagorrus txeT

Currently, Chrome also has its own segmentation API like the one above known as Intl.v8BreakIterator. This segmentation API is nonstandard and something that Chrome simply just implements. So, it is subject to change and doesn't work on most browsers. However, if you're curious, this is how it could be done:

const reverse = str => {
  const iterator = Intl.v8BreakIterator(['en'], {type: 'character'});
  const arr = [];
  let pos = iterator.first();
  while (pos !== -1) {
    const current = iterator.current();
    const nextPos =;
    if (nextPos === -1) break;
    const slice = str.slice(current, nextPos);
  return arr.join("");

console.log(reverse('foo  bar mañana man~ana')); // anan~am anañam rab  oof
console.log(reverse('This  emoji is happy')); // yppah si ijome  sihT
console.log(reverse('Text surrogate pair  composite pair mo¨o varient selector ?? & ZWJ ??')); // ?? JWZ & ?? rotceles tneirav oo¨m riap etisopmoc  riap etagorrus txeT

x86 Assembly on a Mac

For a nice step-by-step x86 Mac-specific introduction see The other links I’ve tried have some non-Mac pitfalls.

A cycle was detected in the build path of project xxx - Build Path Problem

I faced this same problem today. The error was apt. By mistake, I added cyclic dependency. A was dependent on B. In my case, by mistake, apart from adding B as dependent to A. I added A as dependent to B too. It was a foolish mistake.

Hiding a password in a python script (insecure obfuscation only)

There are several ROT13 utilities written in Python on the 'Net -- just google for them. ROT13 encode the string offline, copy it into the source, decode at point of transmission.

But this is really weak protection...

How to suppress Pandas Future warning ?

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

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

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

import warnings

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

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

Unzipping files

If you need to support other formats as well or just need good performance, you can use this WebAssembly library

it's promised based, it uses WebWorkers for threading and API is actually simple ES module

How to get the file extension in PHP?

You could try with this for mime type

$image = getimagesize($_FILES['image']['tmp_name']);

$image['mime'] will return the mime type.

This function doesn't require GD library. You can find the documentation here.

This returns the mime type of the image.

Some people use the $_FILES["file"]["type"] but it's not reliable as been given by the browser and not by PHP.

You can use pathinfo() as ThiefMaster suggested to retrieve the image extension.

First make sure that the image is being uploaded successfully while in development before performing any operations with the image.

How to make HTML open a hyperlink in another window or tab?

use target="_blank"

<a target='_blank' href="">Starfall</a>

jQuery equivalent of JavaScript's addEventListener method

Here is an excellent treatment on the Mozilla Development Network (MDN) of this issue for standard JavaScript (if you do not wish to rely on jQuery or understand it better in general):

Here is a discussion of event flow from a link in the above treatment:

Some key points are:

  • It allows adding more than a single handler for an event
  • It gives you finer-grained control of the phase when the listener gets activated (capturing vs. bubbling)
  • It works on any DOM element, not just HTML elements
  • The value of "this" passed to the event is not the global object (window), but the element from which the element is fired. This is very convenient.
  • Code for legacy IE browsers is simple and included under the heading "Legacy Internet Explorer and attachEvent"
  • You can include parameters if you enclose the handler in an anonymous function

Clicking URLs opens default browser

Arulx Z's answer was exactly what I was looking for.

I'm writing an app with Navigation Drawer with recyclerview and webviews, for keeping the web browsing inside the app regardless of hyperlinks clicked (thus not launching the external web browser). For that it will suffice to put the following 2 lines of code:

mWebView.setWebChromeClient(new WebChromeClient()); mWebView.setWebViewClient(new WebViewClient());?

exactly under your WebView statement.

Here's a example of my implemented WebView code:

public class WebView1 extends AppCompatActivity {

public void onCreate(Bundle savedInstanceState) {

    WebView wv = (WebView) findViewById(; //webview statement
    wv.setWebViewClient(new WebViewClient());    //the lines of code added
    wv.setWebChromeClient(new WebChromeClient()); //same as above


this way, every link clicked in the website will load inside your WebView. (Using Android Studio 1.2.2 with all SDK's updated)

How can I parse a CSV string with JavaScript, which contains comma in data?

I liked FakeRainBrigand's answer, however it contains a few problems: It can not handle whitespace between a quote and a comma, and does not support 2 consecutive commas. I tried editing his answer but my edit got rejected by reviewers that apparently did not understand my code. Here is my version of FakeRainBrigand's code. There is also a fiddle:

String.prototype.splitCSV = function() {
        var matches = this.match(/(\s*"[^"]+"\s*|\s*[^,]+|,)(?=,|$)/g);
        for (var n = 0; n < matches.length; ++n) {
            matches[n] = matches[n].trim();
            if (matches[n] == ',') matches[n] = '';
        if (this[0] == ',') matches.unshift("");
        return matches;

var string = ',"string, duppi, du" , 23 ,,, "string, duppi, du",dup,"", , lala';
var parsed = string.splitCSV();

Extract public/private key from PKCS12 file for later use in SSH-PK-Authentication

OpenSSH cannot use PKCS#12 files out of the box. As others suggested, you must extract the private key in PEM format which gets you from the land of OpenSSL to OpenSSH. Other solutions mentioned here don’t work for me. I use OS X 10.9 Mavericks (10.9.3 at the moment) with “prepackaged” utilities (OpenSSL 0.9.8y, OpenSSH 6.2p2).

First, extract a private key in PEM format which will be used directly by OpenSSH:

openssl pkcs12 -in filename.p12 -clcerts -nodes -nocerts | openssl rsa > ~/.ssh/id_rsa

I strongly suggest to encrypt the private key with password:

openssl pkcs12 -in filename.p12 -clcerts -nodes -nocerts | openssl rsa -passout 'pass:Passw0rd!' > ~/.ssh/id_rsa

Obviously, writing a plain-text password on command-line is not safe either, so you should delete the last command from history or just make sure it doesn’t get there. Different shells have different ways. You can prefix your command with space to prevent it from being saved to history in Bash and many other shells. Here is also how to delete the command from history in Bash:

history -d $(history | tail -n 2 | awk 'NR == 1 { print $1 }')

Alternatively, you can use different way to pass a private key password to OpenSSL - consult OpenSSL documentation for pass phrase arguments.

Then, create an OpenSSH public key which can be added to authorized_keys file:

ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/

Making a <button> that's a link in HTML

<a id="reset-authenticator" asp-page="./ResetAuthenticator"><input type="button" class="btn btn-primary" value="Reset app" /></a>

Python Write bytes to file

Write bytes and Create the file if not exists:

f = open('./put/your/path/here.png', 'wb')

wb means open the file in write binary mode.

How to change the Text color of Menu item in Android?

This is how you can color a specific menu item with color, works for all API levels:

public static void setToolbarMenuItemTextColor(final Toolbar toolbar,
                                               final @ColorRes int color,
                                               @IdRes final int resId) {
    if (toolbar != null) {
        for (int i = 0; i < toolbar.getChildCount(); i++) {
            final View view = toolbar.getChildAt(i);
            if (view instanceof ActionMenuView) {
                final ActionMenuView actionMenuView = (ActionMenuView) view;
                // view children are accessible only after layout-ing
       Runnable() {
                    public void run() {
                        for (int j = 0; j < actionMenuView.getChildCount(); j++) {
                            final View innerView = actionMenuView.getChildAt(j);
                            if (innerView instanceof ActionMenuItemView) {
                                final ActionMenuItemView itemView = (ActionMenuItemView) innerView;
                                if (resId == itemView.getId()) {
                                    itemView.setTextColor(ContextCompat.getColor(toolbar.getContext(), color));

By doing that you loose the background selector effect, so here is the code to apply a custom background selector to all of the menu item children.

public static void setToolbarMenuItemsBackgroundSelector(final Context context,
                                                         final Toolbar toolbar) {
    if (toolbar != null) {
        for (int i = 0; i < toolbar.getChildCount(); i++) {
            final View view = toolbar.getChildAt(i);
            if (view instanceof ImageButton) {
                // left toolbar icon (navigation, hamburger, ...)
                UiHelper.setViewBackgroundSelector(context, view);
            } else if (view instanceof ActionMenuView) {
                final ActionMenuView actionMenuView = (ActionMenuView) view;

                // view children are accessible only after layout-ing
       Runnable() {
                    public void run() {
                        for (int j = 0; j < actionMenuView.getChildCount(); j++) {
                            final View innerView = actionMenuView.getChildAt(j);
                            if (innerView instanceof ActionMenuItemView) {
                                // text item views
                                final ActionMenuItemView itemView = (ActionMenuItemView) innerView;
                                UiHelper.setViewBackgroundSelector(context, itemView);

                                // icon item views
                                for (int k = 0; k < itemView.getCompoundDrawables().length; k++) {
                                    if (itemView.getCompoundDrawables()[k] != null) {
                                        UiHelper.setViewBackgroundSelector(context, itemView);

Here is the helper function also:

public static void setViewBackgroundSelector(@NonNull Context context, @NonNull View itemView) {
    int[] attrs = new int[]{R.attr.selectableItemBackgroundBorderless};
    TypedArray ta = context.obtainStyledAttributes(attrs);
    Drawable drawable = ta.getDrawable(0);

    ViewCompat.setBackground(itemView, drawable);

How to set default value to the input[type="date"]

You can do something like this:

<input type="date" value="<?php echo date("Y-m-d");?>" name="inicio">

How create a new deep copy (clone) of a List<T>?

Create a generic ICloneable<T> interface which you implement in your Book class so that the class knows how to create a copy of itself.

public interface ICloneable<T>
    T Clone();

public class Book : ICloneable<Book>
    public Book Clone()
        return new Book { /* set properties */ };

You can then use either the linq or ConvertAll methods that Mark mentioned.

List<Book> books_2 = books_1.Select(book => book.Clone()).ToList();


List<Book> books_2 = books_1.ConvertAll(book => book.Clone());

Php artisan make:auth command is not defined

In short and precise, all you need to do is

composer require laravel/ui --dev

php artisan ui vue --auth and then the migrate php artisan migrate.

Just for an overview of Laravel Authentication

Laravel Authentication facilities comes with Guard and Providers, Guards define how users are authenticated for each request whereas Providers define how users are retrieved from you persistent storage.

Database Consideration - By default Laravel includes an App\User Eloquent Model in your app directory.

Auth Namespace - App\Http\Controllers\Auth

Controllers - RegisterController, LoginController, ForgotPasswordController and ResetPasswordController, all names are meaningful and easy to understand!

Routing - Laravel/ui package provides a quick way to scaffold all the routes and views you need for authentication using a few simple commands (as mentioned in the start instead of make:auth).

You can disable any newly created controller, e. g. RegisterController and modify your route declaration like, Auth::routes(['register' => false]); For further detail please look into the Laravel Documentation.

Make <body> fill entire screen?

I think the largely correct way, is to set css to this:

    overflow: hidden;

    margin: 0;
    box-sizing: border-box;

html, body
    height: 100%;

target="_blank" vs. target="_new"

target="_blank" opens a new tab in most browsers.

Unable to execute dex: method ID not in [0, 0xffff]: 65536

The below code helps, if you use Gradle. Allows you to easily remove unneeded Google services (presuming you're using them) to get back below the 65k threshold. All credit to this post:

Edit 2014-10-22: There's been a lot of interesting discussion on the gist referenced above. TLDR? look at this one:

Paste this code at the bottom of your build.gradle file and adjust the list of google services you do not need:

def toCamelCase(String string) {
    String result = ""
    string.findAll("[^\\W]+") { String word ->
        result += word.capitalize()
    return result

afterEvaluate { project ->
    Configuration runtimeConfiguration = project.configurations.getByName('compile')
    ResolutionResult resolution = runtimeConfiguration.incoming.resolutionResult
    // Forces resolve of configuration
    ModuleVersionIdentifier module = resolution.getAllComponents().find {"play-services") }.moduleVersion

    String prepareTaskName = "prepare${toCamelCase("${} ${} ${module.version}")}Library"
    File playServiceRootFolder = project.tasks.find { }.explodedDir

    Task stripPlayServices = project.tasks.create(name: 'stripPlayServices', group: "Strip") {
        inputs.files new File(playServiceRootFolder, "classes.jar")
        outputs.dir playServiceRootFolder
        description 'Strip useless packages from Google Play Services library to avoid reaching dex limit'

        doLast {
            copy {
                from(file(new File(playServiceRootFolder, "classes.jar")))
                rename { fileName ->
                    fileName = "classes_orig.jar"
            tasks.create(name: "stripPlayServices" + module.version, type: Jar) {
                destinationDir = playServiceRootFolder
                archiveName = "classes.jar"
                from(zipTree(new File(playServiceRootFolder, "classes_orig.jar"))) {
                    exclude "com/google/ads/**"
                    exclude "com/google/android/gms/analytics/**"
                    exclude "com/google/android/gms/games/**"
                    exclude "com/google/android/gms/plus/**"
                    exclude "com/google/android/gms/drive/**"
                    exclude "com/google/android/gms/ads/**"
            delete file(new File(playServiceRootFolder, "classes_orig.jar"))

    project.tasks.findAll {'prepare') &&'Dependencies') }.each { Task task ->
        task.dependsOn stripPlayServices

CASE IN statement with multiple values

The question is specific to SQL Server, but I would like to extend Martin Smith's answer.

SQL:2003 standard allows to define multiple values for simple case expression:

          WHEN '1121231','31242323' THEN 1
          WHEN '234523','2342423' THEN 2
       END AS Test
FROM tblClient c;

It is optional feature: Comma-separated predicates in simple CASE expression“ (F263).


CASE <common operand>
     WHEN <expression>[, <expression> ...] THEN <result>
    [WHEN <expression>[, <expression> ...] THEN <result>
    [ELSE <result>]

As for know I am not aware of any RDBMS that actually supports that syntax.

What is the standard way to add N seconds to datetime.time in Python?

You cannot simply add number to datetime because it's unclear what unit is used: seconds, hours, weeks...

There is timedelta class for manipulations with date and time. datetime minus datetime gives timedelta, datetime plus timedelta gives datetime, two datetime objects cannot be added although two timedelta can.

Create timedelta object with how many seconds you want to add and add it to datetime object:

>>> from datetime import datetime, timedelta
>>> t = + timedelta(seconds=3000)
>>> print(t)
datetime.datetime(2018, 1, 17, 21, 47, 13, 90244)

There is same concept in C++: std::chrono::duration.

Salt and hash a password in Python

As of Python 3.4, the hashlib module in the standard library contains key derivation functions which are "designed for secure password hashing".

So use one of those, like hashlib.pbkdf2_hmac, with a salt generated using os.urandom:

from typing import Tuple
import os
import hashlib
import hmac

def hash_new_password(password: str) -> Tuple[bytes, bytes]:
    Hash the provided password with a randomly-generated salt and return the
    salt and hash to store in the database.
    salt = os.urandom(16)
    pw_hash = hashlib.pbkdf2_hmac('sha256', password.encode(), salt, 100000)
    return salt, pw_hash

def is_correct_password(salt: bytes, pw_hash: bytes, password: str) -> bool:
    Given a previously-stored salt and hash, and a password provided by a user
    trying to log in, check whether the password is correct.
    return hmac.compare_digest(
        hashlib.pbkdf2_hmac('sha256', password.encode(), salt, 100000)

# Example usage:
salt, pw_hash = hash_new_password('correct horse battery staple')
assert is_correct_password(salt, pw_hash, 'correct horse battery staple')
assert not is_correct_password(salt, pw_hash, 'Tr0ub4dor&3')
assert not is_correct_password(salt, pw_hash, 'rosebud')

Note that:

  • The use of a 16-byte salt and 100000 iterations of PBKDF2 match the minimum numbers recommended in the Python docs. Further increasing the number of iterations will make your hashes slower to compute, and therefore more secure.
  • os.urandom always uses a cryptographically secure source of randomness
  • hmac.compare_digest, used in is_correct_password, is basically just the == operator for strings but without the ability to short-circuit, which makes it immune to timing attacks. That probably doesn't really provide any extra security value, but it doesn't hurt, either, so I've gone ahead and used it.

For theory on what makes a good password hash and a list of other functions appropriate for hashing passwords with, see

Why use the params keyword?

Might sound stupid, But Params doesn't allow multidimensional array. Whereas you can pass a multidimensional array to a function.

Difference between r+ and w+ in fopen()

There are 2 differences, unlike r+, w+ will:

  • create the file if it does not already exist
  • first truncate it, i.e., will delete its contents

How to update PATH variable permanently from Windows command line?

This script

includes all the necessary Windows API calls which can be refactored for your needs. It is actually an AutoHotkey GUI to change the System PATH easily. Needs to be run as an Administrator.

Allowed characters in filename

On Windows OS create a file and give it a invalid character like \ in the filename. As a result you will get a popup with all the invalid characters in a filename.

enter image description here

How to access child's state in React?

If you already have onChange handler for the individual FieldEditors I don't see why you couldn't just move the state up to the FormEditor component and just pass down a callback from there to the FieldEditors that will update the parent state. That seems like a more React-y way to do it, to me.

Something along the line of this perhaps:

const FieldEditor = ({ value, onChange, id }) => {
  const handleChange = event => {
    const text =;
    onChange(id, text);

  return (
    <div className="field-editor">
      <input onChange={handleChange} value={value} />

const FormEditor = props => {
  const [values, setValues] = useState({});
  const handleFieldChange = (fieldId, value) => {
    setValues({ ...values, [fieldId]: value });

  const fields = => (

  return (
      <pre>{JSON.stringify(values, null, 2)}</pre>

// To add abillity to dynamically add/remove fields keep the list in state
const App = () => {
  const fields = ["field1", "field2", "anotherField"];

  return <FormEditor fields={fields} />;

Original - pre-hooks version:

class FieldEditor extends React.Component {_x000D_
  constructor(props) {_x000D_
    this.handleChange = this.handleChange.bind(this);_x000D_
  handleChange(event) {_x000D_
    const text =;_x000D_
    this.props.onChange(, text);_x000D_
  render() {_x000D_
    return (_x000D_
      <div className="field-editor">_x000D_
        <input onChange={this.handleChange} value={this.props.value} />_x000D_
class FormEditor extends React.Component {_x000D_
  constructor(props) {_x000D_
    this.state = {};_x000D_
    this.handleFieldChange = this.handleFieldChange.bind(this);_x000D_
  handleFieldChange(fieldId, value) {_x000D_
    this.setState({ [fieldId]: value });_x000D_
  render() {_x000D_
    const fields = => (_x000D_
    return (_x000D_
// Convert to class component and add ability to dynamically add/remove fields by having it in state_x000D_
const App = () => {_x000D_
  const fields = ["field1", "field2", "anotherField"];_x000D_
  return <FormEditor fields={fields} />;_x000D_
ReactDOM.render(<App />, document.body);

Why is my JQuery selector returning a n.fn.init[0], and what is it?

Another approach(Inside of $function to asure that the each is executed on document ready):

var ids = [1,2];
    if(ids.indexOf($(item).data('id')) > -1){
       $(item).prop("checked", "checked");

Working fiddle:

What is the n.fn.init[0], and why it is returned? Why are my two seemingly identical JQuery functions returning different things?

Answer: It seems that your elements are not in the DOM yet, when you are trying to find them. As @Rory McCrossan pointed out, the length:0 means that it doesn't find any element based on your search criteria.

About n.fn.init[0], lets look at the core of the Jquery Library:

var jQuery = function( selector, context ) {
   return new jQuery.fn.init( selector, context );

Looks familiar, right?, now in a minified version of jquery, this should looks like:

var n = function( selector, context ) {
   return new n.fn.init( selector, context );

So when you use a selector you are creating an instance of the jquery function; when found an element based on the selector criteria it returns the matched elements; when the criteria does not match anything it returns the prototype object of the function.

How to ignore certain files in Git

Add the following line to .gitignore:


This will exclude Hello.class from git. If you have already committed it, run the following command:

git rm Hello.class

If you want to exclude all class files from git, add the following line to .gitignore:


Shared-memory objects in multiprocessing

If you use an operating system that uses copy-on-write fork() semantics (like any common unix), then as long as you never alter your data structure it will be available to all child processes without taking up additional memory. You will not have to do anything special (except make absolutely sure you don't alter the object).

The most efficient thing you can do for your problem would be to pack your array into an efficient array structure (using numpy or array), place that in shared memory, wrap it with multiprocessing.Array, and pass that to your functions. This answer shows how to do that.

If you want a writeable shared object, then you will need to wrap it with some kind of synchronization or locking. multiprocessing provides two methods of doing this: one using shared memory (suitable for simple values, arrays, or ctypes) or a Manager proxy, where one process holds the memory and a manager arbitrates access to it from other processes (even over a network).

The Manager approach can be used with arbitrary Python objects, but will be slower than the equivalent using shared memory because the objects need to be serialized/deserialized and sent between processes.

There are a wealth of parallel processing libraries and approaches available in Python. multiprocessing is an excellent and well rounded library, but if you have special needs perhaps one of the other approaches may be better.

how to use sqltransaction in c#

Update or Delete with sql transaction

 private void SQLTransaction() {
   try {
     string sConnectionString = "My Connection String";
     string query = "UPDATE [dbo].[MyTable] SET ColumnName = '{0}' WHERE ID = {1}";

     SqlConnection connection = new SqlConnection(sConnectionString);
     SqlCommand command = connection.CreateCommand();
     SqlTransaction transaction = connection.BeginTransaction("");
     command.Transaction = transaction;
     try {
       foreach(DataRow row in dt_MyData.Rows) {
         command.CommandText = string.Format(query, row["ColumnName"].ToString(), row["ID"].ToString());
     } catch (Exception ex) {
       MessageBox.Show(ex.Message, "Error");
   } catch (Exception ex) {
     MessageBox.Show("Problem connect to database.", "Error");

Virtualbox shared folder permissions

Add yourself to the vboxsf group within the guest VM.

Solution 1

Run sudo adduser $USER vboxsf from terminal.
(On Suse it's sudo usermod --append --groups vboxsf $USER)

To take effect you should log out and then log in, or you may need to reboot.

Solution 2

Edit the file /etc/group (you will need root privileges). Look for the line vboxsf:x:999 and add at the end :yourusername -- use this solution if you don't have sudo.

To take effect you should log out and then log in, or you may need to reboot.

Declaring variables in Excel Cells

You can use (hidden) cells as variables. E.g., you could hide Column C, set C1 to


and use it as


Alternatively you can write VBA Macros which set and read a global variable.

Edit: AKX renders my Answer partially incorrect. I had no idea you could name cells in Excel.

BadImageFormatException. This will occur when running in 64 bit mode with the 32 bit Oracle client components installed

I was also getting the same error I checked it my system was in 64 bit and I was using oracle.DataAccess of 32 bit version I added correct 64 version now it got resolved below path for the ref of Oracle.DataAccess.dll

Correct path for 64 bit OS- C:\Oracle\11g_64\product\11.2.0\client_64\\bin\4\Oracle.DataAccess.dll

Correct path for 32 bit OS- C:\Oracle\11g_32\product\11.2.0\client_64\\bin\4\Oracle.DataAccess.dll

What is the difference between Forking and Cloning on GitHub?

  • Forked project is on your online repository (repo).
  • Cloned project is on your local machine (I usually clone after forking the repo).

You can commit on your online repo (or commit on your local repo and then push to your online repo), then send pull request.

Project manager can accept it to get your changes in his main online version.

What does the "+" (plus sign) CSS selector mean?

+ selector is called Adjacent Sibling Selector.

For example, the selector p + p, selects the p elements immediately following the p elements

It can be thought of as a looking outside selector which checks for the immediately following element.

Here is a sample snippet to make things more clear:

body {_x000D_
  font-family: Tahoma;_x000D_
  font-size: 12px;_x000D_
p + p {_x000D_
  margin-left: 10px;_x000D_
  <p>Header paragraph</p>_x000D_
  <p>This is a paragraph</p>_x000D_
  <p>This is another paragraph</p>_x000D_
  <p>This is yet another paragraph</p>_x000D_
  <p>Footer paragraph</p>_x000D_

Since we are one the same topic, it is worth mentioning another selector, ~ selector, which is General Sibling Selector

For example, p ~ p selects all the p which follows the p doesn't matter where it is, but both p should be having the same parent.

Here is how it looks like with the same markup:

body {_x000D_
  font-family: Tahoma;_x000D_
  font-size: 12px;_x000D_
p ~ p {_x000D_
  margin-left: 10px;_x000D_
  <p>Header paragraph</p>_x000D_
  <p>This is a paragraph</p>_x000D_
  <p>This is another paragraph</p>_x000D_
  <p>This is yet another paragraph</p>_x000D_
  <p>Footer paragraph</p>_x000D_

Notice that the last p is also matched in this sample.

LINQ Group By and select collection

you can achive it with group join

var result = (from c in Customers
          join oi in OrderItems on c.Id equals oi.Order.Customer.Id into g
          Select new { customer = c, orderItems = g});

c is Customer and g is the customers order items.

How to populate a dropdownlist with json data in jquery?

//teams.Table does not exist

function OnSuccessJSON(data, status) {
    var teams = eval('(' + data.d + ')');
    var listItems = "";
    for (var i = 0; i < teams.length; i++) {
      listItems += "<option value='" + teams[i][0]+ "'>" + teams[i][1] + "</option>";

Using JQuery to open a popup window and print

You should put the print function in your view-details.php file and call it once the file is loaded, by either using

<body onload="window.print()"> 


$(document).ready(function () { 

Expected corresponding JSX closing tag for input Reactjs

You need to close the input element with a /> at the end.

<input id="icon_prefix" type="text" class="validate" />

How do I update the element at a certain position in an ArrayList?

Let arrList be the ArrayList and newValue the new String, then just do:

arrList.set(5, newValue);

This can be found in the java api reference here.

how to set font size based on container size?

If you want to scale it depending on the element width, you can use this web component:

Check the demo here:

The usage is like this:

<full-width-text>Lorem Ipsum</full-width-text>

Take n rows from a spark dataframe and pass to toPandas()

You can use the limit(n) function:

l = [('Alice', 1),('Jim',2),('Sandra',3)]
df = sqlContext.createDataFrame(l, ['name', 'age'])
df.limit(2).withColumn('age2', df.age + 2).toPandas()


l = [('Alice', 1),('Jim',2),('Sandra',3)]
df = sqlContext.createDataFrame(l, ['name', 'age'])
df.withColumn('age2', df.age + 2).limit(2).toPandas()

Why can't decimal numbers be represented exactly in binary?

For example, the number 61.0 has an exact binary representation because the integral portion of any number is always exact. But the number 6.10 is not exact. All I did was move the decimal one place and suddenly I've gone from Exactopia to Inexactville. Mathematically, there should be no intrinsic difference between the two numbers -- they're just numbers.

Let's step away for a moment from the particulars of bases 10 and 2. Let's ask - in base b, what numbers have terminating representations, and what numbers don't? A moment's thought tells us that a number x has a terminating b-representation if and only if there exists an integer n such that x b^n is an integer.

So, for example, x = 11/500 has a terminating 10-representation, because we can pick n = 3 and then x b^n = 22, an integer. However x = 1/3 does not, because whatever n we pick we will not be able to get rid of the 3.

This second example prompts us to think about factors, and we can see that for any rational x = p/q (assumed to be in lowest terms), we can answer the question by comparing the prime factorisations of b and q. If q has any prime factors not in the prime factorisation of b, we will never be able to find a suitable n to get rid of these factors.

Thus for base 10, any p/q where q has prime factors other than 2 or 5 will not have a terminating representation.

So now going back to bases 10 and 2, we see that any rational with a terminating 10-representation will be of the form p/q exactly when q has only 2s and 5s in its prime factorisation; and that same number will have a terminating 2-representatiion exactly when q has only 2s in its prime factorisation.

But one of these cases is a subset of the other! Whenever

q has only 2s in its prime factorisation

it obviously is also true that

q has only 2s and 5s in its prime factorisation

or, put another way, whenever p/q has a terminating 2-representation, p/q has a terminating 10-representation. The converse however does not hold - whenever q has a 5 in its prime factorisation, it will have a terminating 10-representation , but not a terminating 2-representation. This is the 0.1 example mentioned by other answers.

So there we have the answer to your question - because the prime factors of 2 are a subset of the prime factors of 10, all 2-terminating numbers are 10-terminating numbers, but not vice versa. It's not about 61 versus 6.1 - it's about 10 versus 2.

As a closing note, if by some quirk people used (say) base 17 but our computers used base 5, your intuition would never have been led astray by this - there would be no (non-zero, non-integer) numbers which terminated in both cases!

How to set IE11 Document mode to edge as default?

unchecked the "Automatically detect settings" in the Local Area Network Settings (found in "Internet Options" > Connections > LAN Settings.

Can I use CASE statement in a JOIN condition?

Here I have compared the difference in two different result sets:

SELECT main.ColumnName, compare.Value PreviousValue,  main.Value CurrentValue
    SELECT 'Name' AS ColumnName, 'John' as Value UNION ALL
    SELECT 'UserName' AS ColumnName, 'jh001' as Value UNION ALL
    SELECT 'Department' AS ColumnName, 'HR' as Value UNION ALL
    SELECT 'Phone' AS ColumnName, NULL as Value UNION ALL
    SELECT 'DOB' AS ColumnName, '1993-01-01' as Value UNION ALL
    SELECT 'CreateDate' AS ColumnName, '2017-01-01' as Value UNION ALL
    SELECT 'IsActive' AS ColumnName, '1' as Value
) main
    SELECT 'Name' AS ColumnName, 'Rahul' as Value UNION ALL
    SELECT 'UserName' AS ColumnName, 'rh001' as Value UNION ALL
    SELECT 'Department' AS ColumnName, 'HR' as Value UNION ALL
    SELECT 'Phone' AS ColumnName, '01722112233' as Value UNION ALL
    SELECT 'DOB' AS ColumnName, '1993-01-01' as Value UNION ALL
    SELECT 'CreateDate' AS ColumnName, '2017-01-01' as Value UNION ALL
    SELECT 'IsActive' AS ColumnName, '1' as Value
) compare
ON main.ColumnName = compare.ColumnName AND
    WHEN main.Value IS NULL AND compare.Value IS NULL THEN 0
    WHEN main.Value IS NULL AND compare.Value IS NOT NULL THEN 1
    WHEN main.Value IS NOT NULL AND compare.Value IS NULL THEN 1
    WHEN main.Value <> compare.Value THEN 1
END = 1 

How to prevent a double-click using jQuery?

Double click behaves as one single click

"It is inadvisable to bind handlers to both the click and dblclick events for the same element. The sequence of events triggered varies from browser to browser, with some receiving two click events before the dblclick and others only one. Double-click sensitivity (maximum time between clicks that is detected as a double click) can vary by operating system and browser, and is often user-configurable."

That way we have to check what is the event that is being executed at any sequence. 

       var totalClicks = 1;

 $('#elementId').on('click dblclick', function (e) {

 if (e.type == "dblclick") {
    console.log("e.type1: " + e.type);
 } else if (e.type == "click") {

    if (totalClicks > 1) {
        console.log("e.type2: " + e.type);
        totalClicks = 1;
    } else {
        console.log("e.type3: " + e.type);

    //execute the code you want to execute


How to fetch data from local JSON file on react native?

Since React Native 0.4.3 you can read your local JSON file like this:

const customData = require('./customData.json');

and then access customData like a normal JS object.

How to download source in ZIP format from GitHub?

You can also publish a version release on Github, and there's an option to download the source code of that release in a zip file.

You can then share the zip file link to anyone to download the project source code.

Getting individual colors from a color map in matplotlib

In order to get rgba integer value instead of float value, we can do

rgba = cmap(0.5,bytes=True)

So to simplify the code based on answer from Ffisegydd, the code would be like this:

#import colormap
from matplotlib import cm

#normalize item number values to colormap
norm = matplotlib.colors.Normalize(vmin=0, vmax=1000)

#colormap possible values = viridis, jet, spectral
rgba_color = cm.jet(norm(400),bytes=True) 

#400 is one of value between 0 and 1000

Removing double quotes from variables in batch file creates problems with CMD environment

@echo off

Setlocal enabledelayedexpansion

Set 1=%1

Set 1=!1:"=!

Echo !1!

Echo "!1!"

Set 1=

Demonstrates with or without quotes reguardless of whether original parameter has quotes or not.

And if you want to test the existence of a parameter which may or may not be in quotes, put this line before the echos above:

If '%1'=='' goto yoursub

But if checking for existence of a file that may or may not have quotes then it's:

If EXIST "!1!" goto othersub

Note the use of single quotes and double quotes are different.

How to install Anaconda on RaspBerry Pi 3 Model B

On Raspberry Pi 3 Model B - Installation of Miniconda (bundled with Python 3)

Go and get the latest version of miniconda for Raspberry Pi - made for armv7l processor and bundled with Python 3 (eg.: uname -m)


After installation, source your updated .bashrc file with source ~/.bashrc. Then enter the command python --version, which should give you:

Python 3.4.3 :: Continuum Analytics, Inc.

How to compare two Dates without the time portion?

If you're using Java 8, you should use the java.time.* classes to compare dates - it's preferred to the various java.util.* classes


LocalDate date1 = LocalDate.of(2016, 2, 14);
LocalDate date2 = LocalDate.of(2015, 5, 23);

string sanitizer for filename

These may be a bit heavy, but they're flexible enough to sanitize whatever string into a "safe" en style filename or folder name (or heck, even scrubbed slugs and things if you bend it).

1) Building a full filename (with fallback name in case input is totally truncated):

str_file($raw_string, $word_separator, $file_extension, $fallback_name, $length);

2) Or using just the filter util without building a full filename (strict mode true will not allow [] or () in filename):

str_file_filter($string, $separator, $strict, $length);

3) And here are those functions:

// Returns filesystem-safe string after cleaning, filtering, and trimming input
function str_file_filter(
    $sep = '_',
    $strict = false,
    $trim = 248) {

    $str = strip_tags(htmlspecialchars_decode(strtolower($str))); // lowercase -> decode -> strip tags
    $str = str_replace("%20", ' ', $str); // convert rogue %20s into spaces
    $str = preg_replace("/%[a-z0-9]{1,2}/i", '', $str); // remove hexy things
    $str = str_replace("&nbsp;", ' ', $str); // convert all nbsp into space
    $str = preg_replace("/&#?[a-z0-9]{2,8};/i", '', $str); // remove the other non-tag things
    $str = preg_replace("/\s+/", $sep, $str); // filter multiple spaces
    $str = preg_replace("/\.+/", '.', $str); // filter multiple periods
    $str = preg_replace("/^\.+/", '', $str); // trim leading period

    if ($strict) {
        $str = preg_replace("/([^\w\d\\" . $sep . ".])/", '', $str); // only allow words and digits
    } else {
        $str = preg_replace("/([^\w\d\\" . $sep . "\[\]\(\).])/", '', $str); // allow words, digits, [], and ()

    $str = preg_replace("/\\" . $sep . "+/", $sep, $str); // filter multiple separators
    $str = substr($str, 0, $trim); // trim filename to desired length, note 255 char limit on windows

    return $str;

// Returns full file name including fallback and extension
function str_file(
    $sep = '_',
    $ext = '',
    $default = '',
    $trim = 248) {

    // Run $str and/or $ext through filters to clean up strings
    $str = str_file_filter($str, $sep);
    $ext = '.' . str_file_filter($ext, '', true);

    // Default file name in case all chars are trimmed from $str, then ensure there is an id at tail
    if (empty($str) && empty($default)) {
        $str = 'no_name__' . date('Y-m-d_H-m_A') . '__' . uniqid();
    } elseif (empty($str)) {
        $str = $default;

    // Return completed string
    if (!empty($ext)) {
        return $str . $ext;
    } else {
        return $str;

So let's say some user input is: .....&lt;div&gt;&lt;/div&gt;<script></script>&amp; Weiß Göbel ?????File name %20 %20 %21 %2C Décor \/. /. . z \... y \...... x ./ “This name” is & 462^^ not &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; = that grrrreat -][09]()1234747) ???????-??-????????????

And we wanna convert it to something friendlier to make a tar.gz with a file name length of 255 chars. Here is an example use. Note: this example includes a malformed tar.gz extension as a proof of concept, you should still filter the ext after string is built against your whitelist(s).

$raw_str = '.....&lt;div&gt;&lt;/div&gt;<script></script>&amp; Weiß Göbel ?????File name  %20   %20 %21 %2C Décor  \/.  /. .  z \... y \...... x ./  “This name” is & 462^^ not &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; = that grrrreat -][09]()1234747) ???????-??-????????????';
$fallback_str = 'generated_' . date('Y-m-d_H-m_A');
$bad_extension = '....t&+++a()r.gz[]';

echo str_file($raw_str, '_', $bad_extension, $fallback_str);

The output would be: _wei_gbel_file_name_dcor_._._._z_._y_._x_._this_name_is_462_not_that_grrrreat_][09]()1234747)_.tar.gz

You can play with it here:

Or a Gist:

EDIT: updated script filter for &nbsp; instead of space, updated 3v4l link

How to check whether mod_rewrite is enable on server?

just make a new page and add this code

 if(!function_exists('apache_get_modules') ){ phpinfo(); exit; }
 $res = 'Module Unavailable';
 $res = 'Module Available';
<title>A mod_rewrite availability check !</title></head>
<p><?php echo apache_get_version(),"</p><p>mod_rewrite $res"; ?></p>

and run this page then find will able to know module is Available or not if not then you can ask to your hosting or if you want to enable it in local machine then check this youtube step by step tutorial related to enable rewrite module in wamp apache Wamp server icon -> Apache -> Apache Modules and check the rewrite module option

Pandas group-by and sum


You can select different columns to sum numbers.

Position absolute but relative to parent

Incase someone wants to postion a child div directly under a parent

#father {
   position: relative;

#son1 {
   position: absolute;
   top: 100%;

Working demo Codepen

How do I change an HTML selected option using JavaScript?


document.getElementById('personlist').getElementsByTagName('option')[11].selected = 'selected'



IIS - can't access page by ip address instead of localhost

In my case it was because I was using a port other than the default port 80. I was able to access the site locally using localhost but not on another machine using the IP address.

To solve the issue I had to add a firewall inbound rule to allow the port. enter image description here

How to create a trie in Python

Using defaultdict and reduce function.

Create Trie

from functools import reduce
from collections import defaultdict
T = lambda : defaultdict(T)
trie = T()
reduce(dict.__getitem__,'how',trie)['isEnd'] = True

Trie :

defaultdict(<function __main__.<lambda>()>,
            {'h': defaultdict(<function __main__.<lambda>()>,
                         {'o': defaultdict(<function __main__.<lambda>()>,
                                      {'w': defaultdict(<function __main__.<lambda>()>,
                                                   {'isEnd': True})})})})

Search In Trie :

curr = trie
for w in 'how':
    if w in curr:
        curr = curr[w]
        print("Not Found")
if curr['isEnd']:

Fill username and password using selenium in python

In some cases when the element is not interactable, sendKeys() doesn't work and you're likely to encounter an ElementNotInteractableException.

In such cases, you can opt to execute javascript that sets the values and then can post back.


url = ''

driver = Chrome(executable_path="./chromedriver")

username = 'your_username'
password = 'your_password'

#Setting the value of email input field
driver.execute_script(f'var element = document.getElementById("email"); element.value = "{username}";')

#Setting the value of password input field
driver.execute_script(f'var element = document.getElementById("password"); element.value = "{password}";')

#Submitting the form or click the login button also



Max tcp/ip connections on Windows Server 2008

How many thousands of users?

I've run some TCP/IP client/server connection tests in the past on Windows 2003 Server and managed more than 70,000 connections on a reasonably low spec VM. (see here for details: I would be extremely surprised if Windows 2008 Server is limited to less than 2003 Server and, IMHO, the posting that Cloud links to is too vague to be much use. This kind of question comes up a lot, I blogged about why I don't really think that it's something that you should actually worry about here:

Personally I'd test it and see. Even if there is no inherent limit in the Windows 2008 Server version that you intend to use there will still be practical limits based on memory, processor speed and server design.

If you want to run some 'generic' tests you can use my multi-client connection test and the associated echo server. Detailed here: and here: These are what I used to run my own tests for my server framework and these are what allowed me to create 70,000 active connections on a Windows 2003 Server VM with 760MB of memory.

Edited to add details from the comment below...

If you're already thinking of multiple servers I'd take the following approach.

  1. Use the free tools that I link to and prove to yourself that you can create a reasonable number of connections onto your target OS (beware of the Windows limits on dynamic ports which may cause your client connections to fail, search for MAX_USER_PORT).

  2. during development regularly test your actual server with test clients that can create connections and actually 'do something' on the server. This will help to prevent you building the server in ways that restrict its scalability. See here:

jQuery UI DatePicker - Change Date Format

Here is an out of the box future proof date snippet. Firefox defaults to jquery ui datepicker. Otherwise HTML5 datepicker is used. If FF ever support HTML5 type="date" the script will simply be redundant. Dont forget the three dependencies are needed in the head tag.

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

<!--Form element uses HTML 5 type="date"-->
<div class="form-group row">
    <label for="date" class="col-sm-2 col-form-label"Date</label>
    <div class="col-sm-10">          
       <input type="date" class="form-control" name="date" id="date" placeholder="date">

<!--if the user is using FireFox it          
autoconverts type='date' into type='text'. If the type is text the 
script below will assign the jquery ui datepicker with options-->
  var elem = document.createElement('input');
  elem.setAttribute('type', 'date');

  if ( elem.type === 'text' ) 
    $( "#date" ).datepicker( "option", "dateFormat", 'yy-mm-dd' );     

How do I install a pip package globally instead of locally?

Are you using virtualenv? If yes, deactivate the virtualenv. If you are not using, it is already installed widely (system level). Try to upgrade package.

pip install flake8 --upgrade

".addEventListener is not a function" why does this error occur?

var comment = document.getElementsByClassName("button");_x000D_
function showComment() {_x000D_
  var place = document.getElementById('textfield');_x000D_
  var commentBox = document.createElement('textarea');_x000D_
for (var i in comment) {_x000D_
  comment[i].onclick = function() {_x000D_
<input type="button" class="button" value="1">_x000D_
<input type="button" class="button" value="2">_x000D_
<div id="textfield"></div>

How to declare a global variable in JavaScript

The best way is to use closures, because the window object gets very, very cluttered with properties.


<!DOCTYPE html>
    <script type="text/javascript" src="init.js"></script>
    <script type="text/javascript">
      MYLIBRARY.init(["firstValue", 2, "thirdValue"]);
    <script src="script.js"></script>

    <h1>Hello !</h1>

init.js (based on this answer)

var MYLIBRARY = MYLIBRARY || (function(){
    var _args = {}; // Private

    return {
        init : function(Args) {
            _args = Args;
            // Some other initialising
        helloWorld : function(i) {
            return _args[i];


// Here you can use the values defined in the HTML content as if it were a global variable
var a = "Hello World " + MYLIBRARY.helloWorld(2);


Here's the plnkr. Hope it help !

How to start mongodb shell?

Just type mongod instead of ./mongod. It works for me.

Parse JSON String into List<string>

Since you are using JSON.NET, personally I would go with serialization so that you can have Intellisense support for your object. You'll need a class that represents your JSON structure. You can build this by hand, or you can use something like json2csharp to generate it for you:


public class Person
    public string FirstName { get; set; }
    public string LastName { get; set; }

public class RootObject
    public List<Person> People { get; set; }

Then, you can simply call JsonConvert's methods to deserialize the JSON into an object:

RootObject instance = JsonConvert.Deserialize<RootObject>(json);

Then you have Intellisense:

var firstName = instance.People[0].FirstName;
var lastName = instance.People[0].LastName;

How to implement Enums in Ruby?

Another solution is using OpenStruct. Its pretty straight forward and clean.


# bar.rb
require 'ostruct' # not needed when using Rails

# by patching Array you have a simple way of creating a ENUM-style
class Array
   def to_enum(base=0)

class Bar

    MY_ENUM = 1, TWO: 2, THREE: 3)
    MY_ENUM2 = %w[ONE TWO THREE].to_enum

    def use_enum (value)
        case value
        when MY_ENUM.ONE
            puts "Hello, this is ENUM 1"
        when MY_ENUM.TWO
            puts "Hello, this is ENUM 2"
        when MY_ENUM.THREE
            puts "Hello, this is ENUM 3"
            puts "#{value} not found in ENUM"


# usage
foo =    
foo.use_enum 1
foo.use_enum 2
foo.use_enum 9

# put this code in a file 'bar.rb', start IRB and type: load 'bar.rb'

How can I use JavaScript in Java?

I just wanted to answer something new for this question - J2V8.

Author Ian Bull says "Rhino and Nashorn are two common JavaScript runtimes, but these did not meet our requirements in a number of areas:

Neither support ‘Primitives‘. All interactions with these platforms require wrapper classes such as Integer, Double or Boolean. Nashorn is not supported on Android. Rhino compiler optimizations are not supported on Android. Neither engines support remote debugging on Android.""

Highly Efficient Java & JavaScript Integration

Github link

C# DateTime.ParseExact

Your format string is wrong. Change it to

insert = DateTime.ParseExact(line[i], "M/d/yyyy hh:mm", CultureInfo.InvariantCulture);

Most efficient way to create a zero filled JavaScript array?

I was testing out the great answer by T.J. Crowder, and came up with a recursive merge based on the concat solution that outperforms any in his tests in Chrome (i didn't test other browsers).

function makeRec(len, acc) {
    if (acc == null) acc = [];
    if (len <= 1) return acc;
    var b = makeRec(len >> 1, [0]);
    b = b.concat(b);
    if (len & 1) b = b.concat([0]);
    return b;

call the method with makeRec(29).

what is difference between success and .done() method of $.ajax

In short, decoupling success callback function from the ajax function so later you can add your own handlers without modifying the original code (observer pattern).

Please find more detailed information from here:

How to truncate float values?

# value  value to be truncated
# n  number of values after decimal

value = 0.999782
n = 3

wget ssl alert handshake failure

One alternative is to replace the "https" with "http" in the url that you're trying to download from to just circumvent the SSL connection. Not the most secure solution, but this worked in my case.

How to force a hover state with jQuery?

You will have to use a class, but don't worry, it's pretty simple. First we'll assign your :hover rules to not only apply to physically-hovered links, but also to links that have the classname hovered.

a:hover, a.hovered { color: #ccff00; }

Next, when you click #btn, we'll toggle the .hovered class on the #link.

$("#btn").click(function() {

If the link has the class already, it will be removed. If it doesn't have the class, it will be added.

Calculate compass bearing / heading to location in Android

Ok I figured this out. For anyone else trying to do this you need:

a) heading: your heading from the hardware compass. This is in degrees east of magnetic north

b) bearing: the bearing from your location to the destination location. This is in degrees east of true north.


c) declination: the difference between true north and magnetic north

The heading that is returned from the magnetometer + accelermometer is in degrees east of true (magnetic) north (-180 to +180) so you need to get the difference between north and magnetic north for your location. This difference is variable depending where you are on earth. You can obtain by using GeomagneticField class.

GeomagneticField geoField;

private final LocationListener locationListener = new LocationListener() {
   public void onLocationChanged(Location location) {
      geoField = new GeomagneticField(

Armed with these you calculate the angle of the arrow to draw on your map to show where you are facing in relation to your destination object rather than true north.

First adjust your heading with the declination:

heading += geoField.getDeclination();

Second, you need to offset the direction in which the phone is facing (heading) from the target destination rather than true north. This is the part that I got stuck on. The heading value returned from the compass gives you a value that describes where magnetic north is (in degrees east of true north) in relation to where the phone is pointing. So e.g. if the value is -10 you know that magnetic north is 10 degrees to your left. The bearing gives you the angle of your destination in degrees east of true north. So after you've compensated for the declination you can use the formula below to get the desired result:

heading = myBearing - (myBearing + heading); 

You'll then want to convert from degrees east of true north (-180 to +180) into normal degrees (0 to 360):

Math.round(-heading / 360 + 180)

App not setup: This app is still in development mode

Go to Settings->Basic, on top you will find a Switch button which will say App is in development mode.

enter image description here

Click on in development switch button, it will ask you to make app live, and after providing all necessary things, it will become live.

enter image description here

VBA, if a string contains a certain letter


If myString like "*A*" Then

Access Controller method from another controller in Laravel 5


Is it possible to execute multiple _addItem calls asynchronously using Google Analytics?

From the docs:

_trackTrans() Sends both the transaction and item data to the Google Analytics server. This method should be called after _trackPageview(), and used in conjunction with the _addItem() and addTrans() methods. It should be called after items and transaction elements have been set up.

So, according to the docs, the items get sent when you call trackTrans(). Until you do, you can add items, but the transaction will not be sent.

Edit: Further reading led me here:

Where it clearly says you can start another transaction with an existing ID. When you commit it, the new items you listed will be added to that transaction.

Define a struct inside a class in C++

Something like this:

class Class {
    // visibility will default to private unless you specify it
    struct Struct {
        //specify members here;

mongod command not recognized when trying to connect to a mongodb server

It is probably too late, but for the sake of others (like me) who faced the same problem. It is all about the little '\' at the end of the path variable. When you insert the path to MongoDB's bin directory at the end of the PATH windows variable, do not forget to put the '\' (Backslash) at the end, which tells windows it is a directory and not an executable named bin... e.g. I:\Program Files\MongoDB\Server\3.0\bin\

Add a default value to a column through a migration

For Rails 4+, use change_column_default

def change
  change_column_default :table, :column, value

How to convert a private key to an RSA private key?


ssh-keygen -p -m PEM -f ~/.ssh/id_rsa

Add two numbers and display result in textbox with Javascript

You can simply convert the given number using Number primitive type in JavaScript as shown below.

var c = Number(first) + Number(second);

Set Text property of asp:label in Javascript PROPER way

The label's information is stored in the ViewState input on postback (keep in mind the server knows nothing of the page outside of the form values posted back, which includes your label's text).. you would have to somehow update that on the client side to know what changed in that label, which I'm guessing would not be worth your time.

I'm not entirely sure what problem you're trying to solve here, but this might give you a few ideas of how to go about it:

You could create a hidden field to go along with your label, and anytime you update your label, you'd update that value as well.. then in the code behind set the Text property of the label to be what was in that hidden field.

Upload folder with subfolders using S3 and the AWS console

Execute something similar to the following command:

aws s3 cp local_folder_name s3://s3_bucket_name/local_folder_name/ --recursive

How to store the hostname in a variable in a .bat file?

 set host=%COMPUTERNAME%
 echo %host%

This one enough. no need of extra loops of big coding.

AngularJS: How can I pass variables between controllers?

If you don't want to make service then you can do like this.

var scope = angular.element("#another ctrl scope element id.").scope();
scope.plean_assign = some_value;

What is the difference between '/' and '//' when used for division?

In Python 3.x, 5 / 2 will return 2.5 and 5 // 2 will return 2. The former is floating point division, and the latter is floor division, sometimes also called integer division.

In Python 2.2 or later in the 2.x line, there is no difference for integers unless you perform a from __future__ import division, which causes Python 2.x to adopt the 3.x behavior.

Regardless of the future import, 5.0 // 2 will return 2.0 since that's the floor division result of the operation.

You can find a detailed description at

Array and string offset access syntax with curly braces is deprecated

It's really simple to fix the issue, however keep in mind that you should fork and commit your changes for each library you are using in their repositories to help others as well.

Let's say you have something like this in your code:

$str = "test";

since PHP 7.4 curly braces method to get individual characters inside a string has been deprecated, so change the above syntax into this:

$str = "test";

Fixing the code in the question will look something like this:

public function getRecordID(string $zoneID, string $type = '', string $name = ''): string
    $records = $this->listRecords($zoneID, $type, $name);
    if (isset($records->result[0]->id)) {
        return $records->result[0]->id;
    return false;

Check If array is null or not in php

you can use


to check if the main array is empty or not.

But since you have a SimpleXMLElement object, you need to query the object if it is empty or not. See


if (empty($result) || !isset($result['Tags'])) {
    return false;
if ( !($result['Tags'] instanceof SimpleXMLElement)) {
    return false;
return ($result['Tags']->count());

How do I install the yaml package for Python?

There are three YAML capable packages. Syck (pip install syck) which implements the YAML 1.0 specification from 2002; PyYAML (pip install pyyaml) which follows the YAML 1.1 specification from 2004; and ruamel.yaml which follows the latest (YAML 1.2, from 2009) specification.

You can install the YAML 1.2 compatible package with pip install ruamel.yaml or if you are running a modern version of Debian/Ubuntu (or derivative) with:

sudo apt-get install python-ruamel.yaml

How to initialize an array in one step using Ruby?

You can do

array = ['1', '2', '3']

As others have noted, you can also initialize an array with %w notation like so:

array = %w(1 2 3)


array = %w[1 2 3]

Please note that in both cases each element is a string, rather than an integer. So if you want an array whose elements are integers, you should not wrap each element with apostrophes:

array_of_integers = [1, 2, 3]

Also, you don't need to put comma in between the elements (which is necessary when creating an array without this %w notation). If you do this (which I often did by mistake), as in:

wrong_array = %w(1, 2, 3)

its elements will be three strings ---- "1,", "2,", "3". So if you do:

puts wrong_array

the output will be:


which is not what we want here.

Hope this helps to clarify the point!

Filtering Pandas DataFrames on dates

You can use pd.Timestamp to perform a query and a local reference

import pandas as pd
import numpy as np

df = pd.DataFrame()
ts = pd.Timestamp

df['date'] = np.array(np.arange(10) +, dtype='M8[s]')

print(df.query('date > @ts("20190515T071320")')

with the output

0 2019-05-15 07:13:16
1 2019-05-15 07:13:17
2 2019-05-15 07:13:18
3 2019-05-15 07:13:19
4 2019-05-15 07:13:20
5 2019-05-15 07:13:21
6 2019-05-15 07:13:22
7 2019-05-15 07:13:23
8 2019-05-15 07:13:24
9 2019-05-15 07:13:25

5 2019-05-15 07:13:21
6 2019-05-15 07:13:22
7 2019-05-15 07:13:23
8 2019-05-15 07:13:24
9 2019-05-15 07:13:25

Have a look at the pandas documentation for DataFrame.query, specifically the mention about the local variabile referenced udsing @ prefix. In this case we reference pd.Timestamp using the local alias ts to be able to supply a timestamp string

For vs. while in C programming?

They're all interchangeable; you could pick one type and use nothing but that forever, but usually one is more convenient for a given task. It's like saying "why have switch, you can just use a bunch of if statements" -- true, but if it's a common pattern to check a variable for a set of values, it's convenient and much easier to read if there's a language feature to do that

How to Get a Layout Inflater Given a Context?

You can also use this code to get LayoutInflater:

LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)

Windows service start failure: Cannot start service from the command line or debugger

Watch this video, I had the same question. He shows you how to debug the service as well.

Here are his instructions using the basic C# Windows Service template in Visual Studio 2010/2012.

You add this to the Service1.cs file:

public void onDebug()

You change your Main() to call your service this way if you are in the DEBUG Active Solution Configuration.

static void Main()
    #if DEBUG
    //While debugging this section is used.
    Service1 myService = new Service1();

    //In Release this section is used. This is the "normal" way.
    ServiceBase[] ServicesToRun;
    ServicesToRun = new ServiceBase[] 
        new Service1() 

Keep in mind that while this is an awesome way to debug your service. It doesn't call OnStop() unless you explicitly call it similar to the way we called OnStart(null) in the onDebug() function.

ASP.NET Web Site or ASP.NET Web Application?

One of the key differences is that Websites compile dynamically and create on-the-fly assemblies. Web applicaitons compile into one large assembly.

The distinction between the two has been done away with in Visual Studio 2008.

PhpMyAdmin not working on localhost

All I had to do was load localhost:80/phpmyadmin and then the browser figured it out. After that, localhost/phpmyadmin worked.

How to add a spinner icon to button when it's in the Loading state?

Here is a full-fledged css solution inspired by Bulma. Just add

    .button {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      position: relative;
      min-width: 200px;
      max-width: 100%;
      min-height: 40px;
      text-align: center;
      cursor: pointer;

    @-webkit-keyframes spinAround {
      from {
        -webkit-transform: rotate(0deg);
        transform: rotate(0deg);
      to {
        -webkit-transform: rotate(359deg);
        transform: rotate(359deg);
    @keyframes spinAround {
      from {
        -webkit-transform: rotate(0deg);
        transform: rotate(0deg);
      to {
        -webkit-transform: rotate(359deg);
        transform: rotate(359deg);
    } {
      text-indent: -9999px;
      box-shadow: none;
      font-size: 1rem;
      height: 2.25em;
      line-height: 1.5;
      vertical-align: top;
      padding-bottom: calc(0.375em - 1px);
      padding-left: 0.75em;
      padding-right: 0.75em;
      padding-top: calc(0.375em - 1px);
      white-space: nowrap;
    }  {
      -webkit-animation: spinAround 500ms infinite linear;
      animation: spinAround 500ms infinite linear;
      border: 2px solid #dbdbdb;
      border-radius: 290486px;
      border-right-color: transparent;
      border-top-color: transparent;
      content: "";
      display: block;
      height: 1em;
      position: relative;
      width: 1em;

How to properly -filter multiple strings in a PowerShell copy script

Something like this should work (it did for me). The reason for wanting to use -Filter instead of -Include is that include takes a huge performance hit compared to -Filter.

Below just loops each file type and multiple servers/workstations specified in separate files.

##  This script will pull from a list of workstations in a text file and search for the specified string

## Change the file path below to where your list of target workstations reside
## Change the file path below to where your list of filetypes reside

$filetypes = gc 'pathToListOffiletypes.txt'
$servers = gc 'pathToListOfWorkstations.txt'

##Set the scope of the variable so it has visibility
set-variable -Name searchString -Scope 0
$searchString = 'whatYouAreSearchingFor'

foreach ($server in $servers)

    foreach ($filetype in $filetypes)

    ## below creates the search path.  This could be further improved to exclude the windows directory
    $serverString = "\\"+$server+"\c$\Program Files"

    ## Display the server being queried
    write-host “Server:” $server "searching for " $filetype in $serverString

    Get-ChildItem -Path $serverString -Recurse -Filter $filetype |
    #-Include "*.xml","*.ps1","*.cnf","*.odf","*.conf","*.bat","*.cfg","*.ini","*.config","*.info","*.nfo","*.txt" |
    Select-String -pattern $searchstring | group path | select name | out-file f:\DataCentre\String_Results.txt

    $os = gwmi win32_operatingsystem -computer $server
    $sp = $os | % {$_.servicepackmajorversion}
    $a = $os | % {$_.caption}

    ##  Below will list again the server name as well as its OS and SP
    ##  Because the script may not be monitored, this helps confirm the machine has been successfully scanned
        write-host $server “has completed its " $filetype "scan:” “|” “OS:” $a “SP:” “|” $sp


#end script

Get current domain


//to get the domain

$protocol=strpos(strtolower($_SERVER['SERVER_PROTOCOL']),'https') === FALSE ? 'http' : 'https';

//domain with protocol


//protocol,domain,queryString total **As the $_SERVER['SERVER_NAME'] is not reliable for multi domain hosting!

How can I find out the total physical memory (RAM) of my linux box suitable to be parsed by a shell script?

Add the last 2 entries of /proc/meminfo, they give you the exact memory present on the host.


DirectMap4k:       10240 kB
DirectMap2M:     4184064 kB

10240 + 4184064 = 4194304 kB = 4096 MB.

Javascript: How to pass a function with string parameters as a parameter to another function

One way would be to just escape the quotes properly:

<input type="button" value="click" id="mybtn"

In this case, though, I think a better way to handle this would be to wrap the two handlers in anonymous functions:

<input type="button" value="click" id="mybtn"
                function() { myfuncionOnOK('/myController2/myAction2', 
                             'myParameter2'); },
                function() { myfuncionOnCancel('/myController3/myAction3', 
                             'myParameter3'); });">

And then, you could call them from within myfunction like this:

function myfunction(url, onOK, onCancel)
    // Do whatever myfunction would normally do...

    if (okClicked)

    if (cancelClicked)

That's probably not what myfunction would actually look like, but you get the general idea. The point is, if you use anonymous functions, you have a lot more flexibility, and you keep your code a lot cleaner as well.

Copy multiple files from one directory to another from Linux shell

Use wildcards:

cp /home/ankur/folder/* /home/ankur/dest

If you don't want to copy all the files, you can use braces to select files:

cp /home/ankur/folder/{file{1,2},xyz,abc} /home/ankur/dest

This will copy file1, file2, xyz, and abc.

You should read the sections of the bash man page on Brace Expansion and Pathname Expansion for all the ways you can simplify this.

Another thing you can do is cd /home/ankur/folder. Then you can type just the filenames rather than the full pathnames, and you can use filename completion by typing Tab.

Excel error HRESULT: 0x800A03EC while trying to get range with cell's name

I ran into this error because I was attempting to write a string to a cell which started with an "=".

The solution was to put an "'" (apostrophe) before the equals sign, which is a way to tell excel that you're not, in fact, trying to write a formula, and just want to print the equals sign.

How to add plus one (+1) to a SQL Server column in a SQL Query

You need both a value and a field to assign it to. The value is TableField + 1, so the assignment is:

SET TableField = TableField + 1

Replacing H1 text with a logo image: best method for SEO and accessibility?

For SEO reason:

<div itemscope itemtype="">
 <p id="logo"><a href="/"><span itemprop="Brand">Your business</span> <span class="icon fa-stg"></span> - <span itemprop="makesOffer">sell staff</span></a></p>
   <h1>Your awesome title</h1>

How to identify object types in java

You want instanceof:

if (value instanceof Integer)

This will be true even for subclasses, which is usually what you want, and it is also null-safe. If you really need the exact same class, you could do

if (value.getClass() == Integer.class)


if (Integer.class.equals(value.getClass())

Resizing Images in VB.NET

You can simply use this one line code to resize your image in visual basic .net

Public Shared Function ResizeImage(ByVal InputImage As Image) As Image
        Return New Bitmap(InputImage, New Size(64, 64))
End Function


  1. "InputImage" is the image you want to resize.
  2. "64 X 64" is the required size you may change it as your needs i.e 32X32 etc.

How to make MySQL table primary key auto increment with some prefix

Here is PostgreSQL example without trigger if someone need it on PostgreSQL:

CREATE SEQUENCE messages_seq;

    id CHAR(20) NOT NULL DEFAULT ('message_' || nextval('messages_seq')),
    name CHAR(30) NOT NULL,


How can I get the timezone name in JavaScript?

Try this code refer from here

<script type="text/javascript" src="//">
<script type="text/javascript" src="//">
<script type="text/javascript">
    var tz = jstz.determine(); // Determines the time zone of the browser client
    var timezone =; //'Asia/Kolhata' for Indian Time.


sql server convert date to string MM/DD/YYYY

select convert(varchar(10), cast(fmdate as date), 101) from sery

Without cast I was not getting fmdate converted, so fmdate was a string.

Representing Directory & File Structure in Markdown Syntax

If you wish to generate it dynamically I recommend using Frontend-md. It is simple to use.

Set style for TextView programmatically

I have only tested with EditText but you can use the method

public void setBackgroundResource (int resid)

to apply a style defined in an XML file.

Sine this method belongs to View I believe it will work with any UI element.


When use getOne and findOne methods Spring Data JPA

while was true, I didn't have any problem with getOne but after setting it to false , i got LazyInitializationException. Then problem was solved by replacing with findById.
Although there is another solution without replacing the getOne method, and that is put @Transactional at method which is calling repository.getOne(id). In this way transaction will exists and session will not be closed in your method and while using entity there would not be any LazyInitializationException.

Read user input inside a loop

Try to change the loop like this:

for line in $(cat filename); do
    read input
    echo $input;

Unit test:

for line in $(cat /etc/passwd); do
    read input
    echo $input;
    echo "[$line]"

List<Map<String, String>> vs List<? extends Map<String, String>>

What I'm missing in the other answers is a reference to how this relates to co- and contravariance and sub- and supertypes (that is, polymorphism) in general and to Java in particular. This may be well understood by the OP, but just in case, here it goes:


If you have a class Automobile, then Car and Truck are their subtypes. Any Car can be assigned to a variable of type Automobile, this is well-known in OO and is called polymorphism. Covariance refers to using this same principle in scenarios with generics or delegates. Java doesn't have delegates (yet), so the term applies only to generics.

I tend to think of covariance as standard polymorphism what you would expect to work without thinking, because:

List<Car> cars;
List<Automobile> automobiles = cars;
// You'd expect this to work because Car is-a Automobile, but
// throws inconvertible types compile error.

The reason of the error is, however, correct: List<Car> does not inherit from List<Automobile> and thus cannot be assigned to each other. Only the generic type parameters have an inherit relationship. One might think that the Java compiler simply isn't smart enough to properly understand your scenario there. However, you can help the compiler by giving him a hint:

List<Car> cars;
List<? extends Automobile> automobiles = cars;   // no error


The reverse of co-variance is contravariance. Where in covariance the parameter types must have a subtype relationship, in contravariance they must have a supertype relationship. This can be considered as an inheritance upper-bound: any supertype is allowed up and including the specified type:

class AutoColorComparer implements Comparator<Automobile>
    public int compare(Automobile a, Automobile b) {
        // Return comparison of colors

This can be used with Collections.sort:

public static <T> void sort(List<T> list, Comparator<? super T> c)

// Which you can call like this, without errors:
List<Car> cars = getListFromSomewhere();
Collections.sort(cars, new AutoColorComparer());

You could even call it with a comparer that compares objects and use it with any type.

When to use contra or co-variance?

A bit OT perhaps, you didn't ask, but it helps understanding answering your question. In general, when you get something, use covariance and when you put something, use contravariance. This is best explained in an answer to Stack Overflow question How would contravariance be used in Java generics?.

So what is it then with List<? extends Map<String, String>>

You use extends, so the rules for covariance applies. Here you have a list of maps and each item you store in the list must be a Map<string, string> or derive from it. The statement List<Map<String, String>> cannot derive from Map, but must be a Map.

Hence, the following will work, because TreeMap inherits from Map:

List<Map<String, String>> mapList = new ArrayList<Map<String, String>>();
mapList.add(new TreeMap<String, String>());

but this will not:

List<? extends Map<String, String>> mapList = new ArrayList<? extends Map<String, String>>();
mapList.add(new TreeMap<String, String>());

and this will not work either, because it does not satisfy the covariance constraint:

List<? extends Map<String, String>> mapList = new ArrayList<? extends Map<String, String>>();
mapList.add(new ArrayList<String>());   // This is NOT allowed, List does not implement Map

What else?

This is probably obvious, but you may have already noted that using the extends keyword only applies to that parameter and not to the rest. I.e., the following will not compile:

List<? extends Map<String, String>> mapList = new List<? extends Map<String, String>>();
mapList.add(new TreeMap<String, Element>())  // This is NOT allowed

Suppose you want to allow any type in the map, with a key as string, you can use extend on each type parameter. I.e., suppose you process XML and you want to store AttrNode, Element etc in a map, you can do something like:

List<? extends Map<String, ? extends Node>> listOfMapsOfNodes = new...;

// Now you can do:
listOfMapsOfNodes.add(new TreeMap<Sting, Element>());
listOfMapsOfNodes.add(new TreeMap<Sting, CDATASection>());

CMD command to check connected USB devices

You could use wmic command:

wmic logicaldisk where drivetype=2 get <DeviceID, VolumeName, Description, ...>

Drivetype 2 indicates that its a removable disk.

How to enable PHP short tags?

 short_open_tag = On

in php.ini And restart your Apache Server.

Setting background-image using jQuery CSS property

For those using an actual URL and not a variable:

$('myObject').css('background-image', 'url(../../example/url.html)');

COLLATION 'utf8_general_ci' is not valid for CHARACTER SET 'latin1'

Firstly run this query


You have character_set_server='latin1'

for eg if CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci replace it to CHARSET=latin1 and remove the collate

You are good to go

How to convert a Base64 string into a Bitmap image to show it in a ImageView?

You can just basically revert your code using some other built in methods.

byte[] decodedString = Base64.decode(encodedImage, Base64.DEFAULT);
Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length); 

Liquibase lock - reasons?

Sometimes truncating or dropping the table DATABASECHANGELOGLOCK doesn't work. I use PostgreSQL database and came across this issue a lot of times. What I do for solving is to rollback the prepared statements running in background for that database. Try to rollback all the prepared statements and try the liquibase changes again.


SELECT gid FROM pg_prepared_xacts WHERE database='database_name';

If above statement returns any record, then rollback that prepared statement with following SQL statement.

ROLLBACK PREPARED 'gid_obtained_from_above_SQL';

in linux terminal, how do I show the folder's last modification date, taking its content into consideration?

If I could, I would vote for the answer by Paulo. I tested it and understood the concept. I can confirm it works. The find command can output many parameters. For example, add the following to the --printf clause:

%a for attributes in the octal format
%n for the file name including a complete path


find Desktop/ -exec stat \{} --printf="%y %n\n" \; | sort -n -r | head -1
2011-02-14 22:57:39.000000000 +0100 Desktop/new file

Let me raise this question as well: Does the author of this question want to solve his problem using Bash or PHP? That should be specified.

PHP cURL vs file_get_contents

This is old topic but on my last test on one my API, cURL is faster and more stable. Sometimes file_get_contents on larger request need over 5 seconds when cURL need only from 1.4 to 1.9 seconds what is double faster.

I need to add one note on this that I just send GET and recive JSON content. If you setup cURL properly, you will have a great response. Just "tell" to cURL what you need to send and what you need to recive and that's it.

On your exampe I would like to do this setup:

$ch =  curl_init('');
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
    curl_setopt($ch, CURLOPT_TIMEOUT, 3);
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Accept: application/json'));
$result = curl_exec($ch);

This request will return data in 0.10 second max

HAProxy redirecting http to https (ssl)


frontend incoming_requsts
        bind *:80
        bind *:443 ssl crt *path_to_cert*.**pem**
        **http-request redirect scheme https unless { ssl_fc }**
        default_backend k8s_nodes

Procedure or function !!! has too many arguments specified

In addition to all the answers provided so far, another reason for causing this exception can happen when you are saving data from list to database using ADO.Net.

Many developers will mistakenly use for loop or foreach and leave the SqlCommand to execute outside the loop, to avoid that make sure that you have like this code sample for example:

public static void Save(List<myClass> listMyClass)
        using (var Scope = new System.Transactions.TransactionScope())
            if (listMyClass.Count > 0)
                for (int i = 0; i < listMyClass.Count; i++)
                    SqlCommand cmd = new SqlCommand("dbo.SP_SaveChanges", myConnection);
                    cmd.CommandType = CommandType.StoredProcedure;

                    cmd.Parameters.AddWithValue("@ID", listMyClass[i].ID);
                    cmd.Parameters.AddWithValue("@FirstName", listMyClass[i].FirstName);
                    cmd.Parameters.AddWithValue("@LastName", listMyClass[i].LastName);

                    catch (SqlException sqe)
                        throw new Exception(sqe.Message);
                    catch (Exception ex)
                        throw new Exception(ex.Message);
                throw new Exception("List is empty");


How to efficiently calculate a running standard deviation?

Here's a "one-liner", spread over multiple lines, in functional programming style:

def variance(data, opt=0):
    return (lambda (m2, i, _): m2 / (opt + i - 1))(
            lambda (m2, i, avg), x:
                m2 + (x - avg) ** 2 * i / (i + 1),
                i + 1,
                avg + (x - avg) / (i + 1)
            (0, 0, 0)))

Reimport a module in python while interactive

Actually, in Python 3 the module imp is marked as DEPRECATED. Well, at least that's true for 3.4.

Instead the reload function from the importlib module should be used:

But be aware that this library had some API-changes with the last two minor versions.

What value could I insert into a bit type column?

If you're using SQL Server, you can set the value of bit fields with 0 and 1


'true' and 'false' (yes, using strings)

...your_bit_field='false'... => equivalent to 0

IntelliJ inspection gives "Cannot resolve symbol" but still compiles code

For Gradle users:

You may need to synchronize your project with your build.gradle file.

You can right-click on your gradle file under the Project pane to do this, but that didn't seem to do anything for me (I suspect a bug in my version). You'll know if this happens because it wont' kick off any IntelliJ tasks that you will be waiting on. Instead, open up the Gradle Tool pane, then click the synchronize (refresh) button. This worked for me where invalidating the cache and restarting did not.

My own circumstance: I was using a Scala project with Gradle and had to do this.

How to compare binary files to check if they are the same?

For finding flash memory defects, I had to write this script which shows all 1K blocks which contain differences (not only the first one as cmp -b does)



size=$(stat -c%s $f1)
while [ $i -lt $size ]; do
  if ! r="`cmp -n 1024 -i $i -b $f1 $f2`"; then
    printf "%8x: %s\n" $i "$r"
  i=$(expr $i + 1024)


   2d400: testinput.dat testoutput.dat differ: byte 3, line 1 is 200 M-^@ 240 M- 
   2dc00: testinput.dat testoutput.dat differ: byte 8, line 1 is 327 M-W 127 W
   4d000: testinput.dat testoutput.dat differ: byte 37, line 1 is 270 M-8 260 M-0
   4d400: testinput.dat testoutput.dat differ: byte 19, line 1 is  46 &  44 $

Disclaimer: I hacked the script in 5 min. It doesn't support command line arguments nor does it support spaces in file names

How do you add multi-line text to a UIButton?

For iOS 6 and above, use the following to allow multiple lines:

button.titleLabel.lineBreakMode = NSLineBreakByWordWrapping;
// you probably want to center it
button.titleLabel.textAlignment = NSTextAlignmentCenter; // if you want to 
[button setTitle: @"Line1\nLine2" forState: UIControlStateNormal];

For iOS 5 and below use the following to allow multiple lines:

button.titleLabel.lineBreakMode = UILineBreakModeWordWrap;
// you probably want to center it
button.titleLabel.textAlignment = UITextAlignmentCenter;
[button setTitle: @"Line1\nLine2" forState: UIControlStateNormal];

2017, for iOS9 forward,

generally, just do these two things:

  1. choose "Attributed Text"
  2. on the "Line Break" popup select "Word Wrap"