Programs & Examples On #Coalescing

What does double question mark (??) operator mean in PHP

$myVar = $someVar ?? 42;

Is equivalent to :

$myVar = isset($someVar) ? $someVar : 42;

For constants, the behaviour is the same when using a constant that already exists :

define("FOO", "bar");
define("BAR", null);

$MyVar = FOO ?? "42";
$MyVar2 = BAR ?? "42";

echo $MyVar . PHP_EOL;  // bar
echo $MyVar2 . PHP_EOL; // 42

However, for constants that don't exist, this is different :

$MyVar3 = IDONTEXIST ?? "42"; // Raises a warning
echo $MyVar3 . PHP_EOL;       // IDONTEXIST

Warning: Use of undefined constant IDONTEXIST - assumed 'IDONTEXIST' (this will throw an Error in a future version of PHP)

Php will convert the non-existing constant to a string.

You can use constant("ConstantName") that returns the value of the constant or null if the constant doesn't exist, but it will still raise a warning. You can prepended the function with the error control operator @ to ignore the warning message :

$myVar = @constant("IDONTEXIST") ?? "42"; // No warning displayed anymore
echo $myVar . PHP_EOL; // 42

PHP Parse error: syntax error, unexpected '?' in helpers.php 233

I had the same error and the problem is that I had not correctly installed Composer.

I am using Windows and I installed Composer-Setup.exe from getcomposer.org and when you have more than one version of PHP installed you must select the version that you are running at this point of the installation

enter image description here

PHP ternary operator vs null coalescing operator

Both are shorthands for longer expressions.

?: is short for $a ? $a : $b. This expression will evaluate to $a if $a evaluates to TRUE.

?? is short for isset($a) ? $a : $b. This expression will evaluate to $a if $a is set and not null.

Their use cases overlaps when $a is undefined or null. When $a is undefined ?? will not produce an E_NOTICE, but the results are the same. When $a is null the result is the same.

Check an integer value is Null in c#

Nullable<T> (or ?) exposes a HasValue flag to denote if a value is set or the item is null.

Also, nullable types support ==:

if (Age == null)

The ?? is the null coalescing operator and doesn't result in a boolean expression, but a value returned:

int i = Age ?? 0;

So for your example:

if (age == null || age == 0)

Or:

if (age.GetValueOrDefault(0) == 0)

Or:

if ((age ?? 0) == 0)

Or ternary:

int i = age.HasValue ? age.Value : 0;

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

I've occasionally found the following idiom useful:

a?.b?.c

can be rewritten as:

((a||{}).b||{}).c

This takes advantage of the fact that getting unknown attributes on an object returns undefined, rather than throwing an exception as it does on null or undefined, so we replace null and undefined with an empty object before navigating.

Is there a Python equivalent of the C# null-coalescing operator?

In case you need to nest more than one null coalescing operation such as:

model?.data()?.first()

This is not a problem easily solved with or. It also cannot be solved with .get() which requires a dictionary type or similar (and cannot be nested anyway) or getattr() which will throw an exception when NoneType doesn't have the attribute.

The relevant pip considering adding null coalescing to the language is PEP 505 and the discussion relevant to the document is in the python-ideas thread.

Reference — What does this symbol mean in PHP?

NullSafe Operator "?->" (possibly) since php8

In PHP8 it's been accepted this new operator, you can find the documentation here. ?-> it's the NullSafe Operator, it returns null in case you try to invoke functions or get values from null...

Examples:

<?php
$obj = null;
$obj = $obj?->attr; //return null
$obj = ?->funct(); // return null
$obj = $objDrive->attr; // Error: Trying to get property 'attr' of non-object
?>

C# elegant way to check if a property's property is null

you can use the following extension and I think it is really good:

/// <summary>
/// Simplifies null checking
/// </summary>
public static TR Get<TF, TR>(TF t, Func<TF, TR> f)
    where TF : class
{
    return t != null ? f(t) : default(TR);
}

/// <summary>
/// Simplifies null checking
/// </summary>
public static TR Get<T1, T2, TR>(T1 p1, Func<T1, T2> p2, Func<T2, TR> p3)
    where T1 : class
    where T2 : class
{
    return Get(Get(p1, p2), p3);
}

/// <summary>
/// Simplifies null checking
/// </summary>
public static TR Get<T1, T2, T3, TR>(T1 p1, Func<T1, T2> p2, Func<T2, T3> p3, Func<T3, TR> p4)
    where T1 : class
    where T2 : class
    where T3 : class
{
    return Get(Get(Get(p1, p2), p3), p4);
}

And it is used like this:

int value = Nulify.Get(objectA, x=>x.PropertyA, x=>x.PropertyB, x=>x.PropertyC);

Is there a "null coalescing" operator in JavaScript?

Yes, it is coming soon. See proposal here and implementation status here.

It looks like this:

x ?? y

Example

const response = {
  settings: {
    nullValue: null,
    height: 400,
    animationDuration: 0,
    headerText: '',
    showSplashScreen: false
  }
};

const undefinedValue = response.settings?.undefinedValue ?? 'some other default'; // result: 'some other default'
const nullValue = response.settings?.nullValue ?? 'some other default'; // result: 'some other default'
const headerText = response.settings?.headerText ?? 'Hello, world!'; // result: ''
const animationDuration = response.settings?.animationDuration ?? 300; // result: 0
const showSplashScreen = response.settings?.showSplashScreen ?? true; // result: false

How do I include a file over 2 directories back?

To include a file one directory back, use '../file'. For two directories back, use '../../file'. And so on.

Although, realistically you shouldn't be performing includes relative to the current directory. What if you wanted to move that file? All of the links would break. A way to ensure that you can still link to other files, while retaining those links if you move your file, is:

require_once($_SERVER['DOCUMENT_ROOT'] . 'directory/directory/file');

DOCUMENT_ROOT is a server variable that represents the base directory that your code is located within.

Get current date in milliseconds

You can just do this:

long currentTime = (long)(NSTimeInterval)([[NSDate date] timeIntervalSince1970]);

this will return a value en milliseconds, so if you multiply the resulting value by 1000 (as suggested my Eimantas) you'll overflow the long type and it'll result in a negative value.

For example, if I run that code right now, it'll result in

currentTime = 1357234941

and

currentTime /seconds / minutes / hours / days = years
1357234941 / 60 / 60 / 24 / 365 = 43.037637652207

ASP.net Getting the error "Access to the path is denied." while trying to upload files to my Windows Server 2008 R2 Web server

If anyone stumbles across this as it is the first result in google,

remember to specify the filename too in the SaveAs method.

Won't work

file_upload.PostedFile.SaveAs(Server.MapPath(SaveLocation));

You need this:

filename = Path.GetFileName(file_upload.PostedFile.FileName);
file_upload.PostedFile.SaveAs(Server.MapPath(SaveLocation + "\\" + filename));

I assumed the SaveAs method will automatically use the filename uploaded. Kept getting "Access denied" error. Not very descriptive of the actual problem

Difference between Relative path and absolute path in javascript

Going Relative:

  • You could download a self-contained directory (maybe a zipped file) and open links from an html or xml locally without need to reach the server. This increases speed performance significantly, specially if you have to deal with a slow network.

Going Absolute:

  • You would have to swallow the network speed, but in terms of security you could prevent certain users to see certain files or increase network traffic if (and only if...) that is good for you.

How do I flush the cin buffer?

Possibly:

std::cin.ignore(INT_MAX);

This would read in and ignore everything until EOF. (you can also supply a second argument which is the character to read until (ex: '\n' to ignore a single line).

Also: You probably want to do a: std::cin.clear(); before this too to reset the stream state.

jQuery - Dynamically Create Button and Attach Event Handler

You were just adding the html string. Not the element you created with a click event listener.

Try This:

<html>
<head>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
</head>
<body>
    <table id="addNodeTable">
        <tr>
            <td>
                Row 1
            </td>
        </tr>
        <tr >
            <td>
                Row 2
            </td>
        </tr>
    </table>
</body>
</html>
<script type="text/javascript">
    $(document).ready(function() {
        var test = $('<button>Test</button>').click(function () {
            alert('hi');
        });
        $("#addNodeTable tr:last").append('<tr><td></td></tr>').find("td:last").append(test);

    });
</script>

Read large files in Java

To save memory, do not unnecessarily store/duplicate the data in memory (i.e. do not assign them to variables outside the loop). Just process the output immediately as soon as the input comes in.

It really doesn't matter whether you're using BufferedReader or not. It will not cost significantly much more memory as some implicitly seem to suggest. It will at highest only hit a few % from performance. The same applies on using NIO. It will only improve scalability, not memory use. It will only become interesting when you've hundreds of threads running on the same file.

Just loop through the file, write every line immediately to other file as you read in, count the lines and if it reaches 100, then switch to next file, etcetera.

Kickoff example:

String encoding = "UTF-8";
int maxlines = 100;
BufferedReader reader = null;
BufferedWriter writer = null;

try {
    reader = new BufferedReader(new InputStreamReader(new FileInputStream("/bigfile.txt"), encoding));
    int count = 0;
    for (String line; (line = reader.readLine()) != null;) {
        if (count++ % maxlines == 0) {
            close(writer);
            writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("/smallfile" + (count / maxlines) + ".txt"), encoding));
        }
        writer.write(line);
        writer.newLine();
    }
} finally {
    close(writer);
    close(reader);
}

Permutations in JavaScript?

Here is a minimal ES6 version. The flatten and without functions can be pulled from Lodash.

const flatten = xs =>
    xs.reduce((cum, next) => [...cum, ...next], []);

const without = (xs, x) =>
    xs.filter(y => y !== x);

const permutations = xs =>
    flatten(xs.map(x =>
        xs.length < 2
            ? [xs]
            : permutations(without(xs, x)).map(perm => [x, ...perm])
    ));

Result:

permutations([1,2,3])
// [[1, 2, 3], [1, 3, 2], [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1]]

Using multiple delimiters in awk

Another one is to use the -F option but pass it regex to print the text between left and or right parenthesis ().

The file content:

528(smbw)
529(smbt)
530(smbn)
10115(smbs)

The command:

awk -F"[()]" '{print $2}' filename

result:

smbw
smbt
smbn
smbs

Using awk to just print the text between []:

Use awk -F'[][]' but awk -F'[[]]' will not work.

http://stanlo45.blogspot.com/2020/06/awk-multiple-field-separators.html

What does "request for member '*******' in something not a structure or union" mean?

It may also happen in the following case:

eg. if we consider the push function of a stack:

typedef struct stack
{
    int a[20];
    int head;
}stack;

void push(stack **s)
{
    int data;
    printf("Enter data:");
    scanf("%d",&(*s->a[++*s->head])); /* this is where the error is*/
}

main()
{
    stack *s;
    s=(stack *)calloc(1,sizeof(stack));
    s->head=-1;
    push(&s);
    return 0;
}

The error is in the push function and in the commented line. The pointer s has to be included within the parentheses. The correct code:

scanf("%d",&( (*s)->a[++(*s)->head]));

How do I set the default schema for a user in MySQL

If your user has a local folder e.g. Linux, in your users home folder you could create a .my.cnf file and provide the credentials to access the server there. for example:-

[client]
host=localhost
user=yourusername
password=yourpassword or exclude to force entry
database=mygotodb

Mysql would then open this file for each user account read the credentials and open the selected database.

Not sure on Windows, I upgraded from Windows because I needed the whole house not just the windows (aka Linux) a while back.

How do I launch the Android emulator from the command line?

For one-click (BATCH file) launch, this is what I've done:

  • got the name of AVD from Android Studio -> Tools -> AVD Manager -> Click on Arrow Down and choose View Details ( for me it's Pixel_2_API_28, so change accordingly below)
  • create an start.bat file and put the following inside:
 c: 
 cd C:\Program Files (x86)\Android\android-sdk\emulator\ 
 emulator -avd Pixel_2_API_28

Explanations:

  • First line: for me was necessary because I am launching it from d:
  • Second line: for me was not working the tools\emulator
  • Third line: make sure you change the name of the AVD with yours (here Pixel_2_API_28)

Using:

  • launch start.bat from command line

Excel cell value as string won't store as string

Use Range("A1").Text instead of .Value

post comment edit:
Why?
Because the .Text property of Range object returns what is literally visible in the spreadsheet, so if you cell displays for example i100l:25he*_92 then <- Text will return exactly what it in the cell including any formatting.
The .Value and .Value2 properties return what's stored in the cell under the hood excluding formatting. Specially .Value2 for date types, it will return the decimal representation.

If you want to dig deeper into the meaning and performance, I just found this article which seems like a good guide

another edit
Here you go @Santosh
type in (MANUALLY) the values from the DEFAULT (col A) to other columns
Do not format column A at all
Format column B as Text
Format column C as Date[dd/mm/yyyy]
Format column D as Percentage
Dont Format column A, Format B as TEXT, C as Date, D as Percentage
now,
paste this code in a module

Sub main()

    Dim ws As Worksheet, i&, j&
    Set ws = Sheets(1)
    For i = 3 To 7
        For j = 1 To 4
            Debug.Print _
                    "row " & i & vbTab & vbTab & _
                    Cells(i, j).Text & vbTab & _
                    Cells(i, j).Value & vbTab & _
                    Cells(i, j).Value2
        Next j
    Next i
End Sub

and Analyse the output! Its really easy and there isn't much more i can do to help :)

            .TEXT              .VALUE             .VALUE2
row 3       hello             hello               hello
row 3       hello             hello               hello
row 3       hello             hello               hello
row 3       hello             hello               hello
row 4       1                 1                   1
row 4       1                 1                   1
row 4       01/01/1900        31/12/1899          1
row 4       1.00%             0.01                0.01
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 5       helo1$$           helo1$$             helo1$$
row 6       63                63                  63
row 6       =7*9              =7*9                =7*9
row 6       03/03/1900        03/03/1900          63
row 6       6300.00%          63                  63
row 7       29/05/2013        29/05/2013          41423
row 7       29/05/2013        29/05/2013          29/05/2013
row 7       29/05/2013        29/05/2013          41423
row 7       29/05/2013%       29/05/2013%         29/05/2013%

Best way to store time (hh:mm) in a database

DATETIME start DATETIME end

I implore you to use two DATETIME values instead, labelled something like event_start and event_end.

Time is a complex business

Most of the world has now adopted the denery based metric system for most measurements, rightly or wrongly. This is good overall, because at least we can all agree that a g, is a ml, is a cubic cm. At least approximately so. The metric system has many flaws, but at least it's internationally consistently flawed.

With time however, we have; 1000 milliseconds in a second, 60 seconds to a minute, 60 minutes to an hour, 12 hours for each half a day, approximately 30 days per month which vary by the month and even year in question, each country has its time offset from others, the way time is formatted in each country vary.

It's a lot to digest, but the long and short of it is impossible for such a complex scenario to have a simple solution.

Some corners can be cut, but there are those where it is wiser not to

Although the top answer here suggests that you store an integer of minutes past midnight might seem perfectly reasonable, I have learned to avoid doing so the hard way.

The reasons to implement two DATETIME values are for an increase in accuracy, resolution and feedback.

These are all very handy for when the design produces undesirable results.

Am I storing more data than required?

It might initially appear like more information is being stored than I require, but there is a good reason to take this hit.

Storing this extra information almost always ends up saving me time and effort in the long-run, because I inevitably find that when somebody is told how long something took, they'll additionally want to know when and where the event took place too.

It's a huge planet

In the past, I have been guilty of ignoring that there are other countries on this planet aside from my own. It seemed like a good idea at the time, but this has ALWAYS resulted in problems, headaches and wasted time later on down the line. ALWAYS consider all time zones.

C#

A DateTime renders nicely to a string in C#. The ToString(string Format) method is compact and easy to read.

E.g.

new TimeSpan(EventStart.Ticks - EventEnd.Ticks).ToString("h'h 'm'm 's's'")

SQL server

Also if you're reading your database seperate to your application interface, then dateTimes are pleasnat to read at a glance and performing calculations on them are straightforward.

E.g.

SELECT DATEDIFF(MINUTE, event_start, event_end)

ISO8601 date standard

If using SQLite then you don't have this, so instead use a Text field and store it in ISO8601 format eg.

"2013-01-27T12:30:00+0000"

Notes:

  • This uses 24 hour clock*

  • The time offset (or +0000) part of the ISO8601 maps directly to longitude value of a GPS coordiate (not taking into account daylight saving or countrywide).

E.g.

TimeOffset=(±Longitude.24)/360 

...where ± refers to east or west direction.

It is therefore worth considering if it would be worth storing longitude, latitude and altitude along with the data. This will vary in application.

  • ISO8601 is an international format.

  • The wiki is very good for further details at http://en.wikipedia.org/wiki/ISO_8601.

  • The date and time is stored in international time and the offset is recorded depending on where in the world the time was stored.

In my experience there is always a need to store the full date and time, regardless of whether I think there is when I begin the project. ISO8601 is a very good, futureproof way of doing it.

Additional advice for free

It is also worth grouping events together like a chain. E.g. if recording a race, the whole event could be grouped by racer, race_circuit, circuit_checkpoints and circuit_laps.

In my experience, it is also wise to identify who stored the record. Either as a seperate table populated via trigger or as an additional column within the original table.

The more you put in, the more you get out

I completely understand the desire to be as economical with space as possible, but I would rarely do so at the expense of losing information.

A rule of thumb with databases is as the title says, a database can only tell you as much as it has data for, and it can be very costly to go back through historical data, filling in gaps.

The solution is to get it correct first time. This is certainly easier said than done, but you should now have a deeper insight of effective database design and subsequently stand a much improved chance of getting it right the first time.

The better your initial design, the less costly the repairs will be later on.

I only say all this, because if I could go back in time then it is what I'd tell myself when I got there.

How to call function on child component on parent events

The below example is self explainatory. where refs and events can be used to call function from and to parent and child.

// PARENT
<template>
  <parent>
    <child
      @onChange="childCallBack"
      ref="childRef"
      :data="moduleData"
    />
    <button @click="callChild">Call Method in child</button>
  </parent>
</template>

<script>
export default {
  methods: {
    callChild() {
      this.$refs.childRef.childMethod('Hi from parent');
    },
    childCallBack(message) {
      console.log('message from child', message);
    }
  }
};
</script>

// CHILD
<template>
  <child>
    <button @click="callParent">Call Parent</button>
  </child>
</template>

<script>
export default {
  methods: {
    callParent() {
      this.$emit('onChange', 'hi from child');
    },
    childMethod(message) {
      console.log('message from parent', message);
    }
  }
}
</script>

What is the purpose of the return statement?

This answer goes over some of the cases that have not been discussed above.
The return statement allows you to terminate the execution of a function before you reach the end. This causes the flow of execution to immediately return to the caller.

In line number 4:

def ret(n):
    if n > 9:
         temp = "two digits"
         return temp     #Line 4        
    else:
         temp = "one digit"
         return temp     #Line 8
    print("return statement")
ret(10)

After the conditional statement gets executed the ret() function gets terminated due to return temp (line 4). Thus the print("return statement") does not get executed.

Output:

two digits   

This code that appears after the conditional statements, or the place the flow of control cannot reach, is the dead code.

Returning Values
In lines number 4 and 8, the return statement is being used to return the value of a temporary variable after the condition has been executed.

To bring out the difference between print and return:

def ret(n):
    if n > 9:
        print("two digits")
        return "two digits"           
    else :
        print("one digit")
        return "one digit"        
ret(25)

Output:

two digits
'two digits'

HTML5 Canvas 100% Width Height of Viewport?

I was looking to find the answer to this question too, but the accepted answer was breaking for me. Apparently using window.innerWidth isn't portable. It does work in some browsers, but I noticed Firefox didn't like it.

Gregg Tavares posted a great resource here that addresses this issue directly: http://webglfundamentals.org/webgl/lessons/webgl-anti-patterns.html (See anti-pattern #'s 3 and 4).

Using canvas.clientWidth instead of window.innerWidth seems to work nicely.

Here's Gregg's suggested render loop:

function resize() {
  var width = gl.canvas.clientWidth;
  var height = gl.canvas.clientHeight;
  if (gl.canvas.width != width ||
      gl.canvas.height != height) {
     gl.canvas.width = width;
     gl.canvas.height = height;
     return true;
  }
  return false;
}

var needToRender = true;  // draw at least once
function checkRender() {
   if (resize() || needToRender) {
     needToRender = false;
     drawStuff();
   }
   requestAnimationFrame(checkRender);
}
checkRender();

Question mark characters displaying within text, why is this?

I had this issue so I just took all my content, copy/pasted it into notepad, made a new php file, pasted back in, re-saved and overwrote, and.. that worked! It really was some relic of Microsoft Word editing...

TypeError: 'float' object is not subscriptable

PizzaChange=float(input("What would you like the new price for all standard pizzas to be? "))      
for i,price in enumerate(PriceList):
  PriceList[i] = PizzaChange + 3*int(i>=7)

sqlalchemy IS NOT NULL select

column_obj != None will produce a IS NOT NULL constraint:

In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL.

or use isnot() (new in 0.7.9):

Implement the IS NOT operator.

Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.

Demo:

>>> from sqlalchemy.sql import column
>>> column('YourColumn') != None
<sqlalchemy.sql.elements.BinaryExpression object at 0x10c8d8b90>
>>> str(column('YourColumn') != None)
'"YourColumn" IS NOT NULL'
>>> column('YourColumn').isnot(None)
<sqlalchemy.sql.elements.BinaryExpression object at 0x104603850>
>>> str(column('YourColumn').isnot(None))
'"YourColumn" IS NOT NULL'

Regular expression - starting and ending with a character string

This should do it for you ^wp.*php$

Matches

wp-comments-post.php
wp.something.php
wp.php

Doesn't match

something-wp.php
wp.php.txt

Passing Parameters JavaFX FXML

Here is an example for using a controller injected by Guice.

/**
 * Loads a FXML file and injects its controller from the given Guice {@code Provider}
 */
public abstract class GuiceFxmlLoader {

   public GuiceFxmlLoader(Stage stage, Provider<?> provider) {
      mStage = Objects.requireNonNull(stage);
      mProvider = Objects.requireNonNull(provider);
   }

   /**
    * @return the FXML file name
    */
   public abstract String getFileName();

   /**
    * Load FXML, set its controller with given {@code Provider}, and add it to {@code Stage}.
    */
   public void loadView() {
      try {
         FXMLLoader loader = new FXMLLoader(getClass().getClassLoader().getResource(getFileName()));
         loader.setControllerFactory(p -> mProvider.get());
         Node view = loader.load();
         setViewInStage(view);
      }
      catch (IOException ex) {
         LOGGER.error("Failed to load FXML: " + getFileName(), ex);
      }
   }

   private void setViewInStage(Node view) {
      BorderPane pane = (BorderPane)mStage.getScene().getRoot();
      pane.setCenter(view);
   }

   private static final Logger LOGGER = Logger.getLogger(GuiceFxmlLoader.class);

   private final Stage mStage;
   private final Provider<?> mProvider;
}

Here is a concrete implementation of the loader:

public class ConcreteViewLoader extends GuiceFxmlLoader {

   @Inject
   public ConcreteViewLoader(Stage stage, Provider<MyController> provider) {
      super(stage, provider);
   }

   @Override
   public String getFileName() {
      return "my_view.fxml";
   }
}

Note this example loads the view into the center of a BoarderPane that is the root of the Scene in the Stage. This is irrelevant to the example (implementation detail of my specific use case) but decided to leave it in as some may find it useful.

SQL- Ignore case while searching for a string

Like this.

SELECT DISTINCT COL_NAME FROM myTable WHERE COL_NAME iLIKE '%Priceorder%'

In postgresql.

Use table name in MySQL SELECT "AS"

SELECT field1, field2, 'Test' AS field3 FROM Test; // replace with simple quote '

Getting time elapsed in Objective-C

use the timeIntervalSince1970 function of the NSDate class like below:

double start = [startDate timeIntervalSince1970];
double end = [endDate timeIntervalSince1970];
double difference = end - start;

basically, this is what i use to compare the difference in seconds between 2 different dates. also check this link here

Get the first element of an array

No one has suggested using the ArrayIterator class:

$array = array( 4 => 'apple', 7 => 'orange', 13 => 'plum' );
$first_element = (new ArrayIterator($array))->current();
echo $first_element; //'apple'

gets around the by reference stipulation of the OP.

how to add lines to existing file using python

Open the file for 'append' rather than 'write'.

with open('file.txt', 'a') as file:
    file.write('input')

Emulator: ERROR: x86 emulation currently requires hardware acceleration

This answer works for latest update on Windows 10 version 1709. Not tried with other version. But i hope it'll work.

I also ran into similar issue in my windows 10 system. I disabled Hyper-V and I tried all the answers posted here. But after that also i faced the same issue. So after lot of try, made it work using an documentation available in haxm manual. The document menntioned to use a tool named Device Guard and Credential Guard hardware readiness tool provided by Microsoft to disable Hyper-V along with some other features(Remember not only Hyper-V. So little cautios) completely. Follow the below steps to do that.

  1. Download the latest version of the tool from here.
  2. Unzip.
  3. Open an elevated (i.e. Run as administrator) Command Prompt and run the below command by changing the extrated path and the respective version number.

@powershell -ExecutionPolicy RemoteSigned -Command "X:\path\to\dgreadiness_v3.6\DG_Readiness_Tool_v3.6.ps1 -Disable"

  1. Reboot.

Then if you try to install intel haxm, it'll work.

In case of latest update check the docs available in official intel haxm development link.

Hope it helps someone.

How to generate a core dump in Linux on a segmentation fault?

This depends on what shell you are using. If you are using bash, then the ulimit command controls several settings relating to program execution, such as whether you should dump core. If you type

ulimit -c unlimited

then that will tell bash that its programs can dump cores of any size. You can specify a size such as 52M instead of unlimited if you want, but in practice this shouldn't be necessary since the size of core files will probably never be an issue for you.

In tcsh, you'd type

limit coredumpsize unlimited

Can HTTP POST be limitless?

In an application I was developing I ran into what appeared to be a POST limit of about 2KB. It turned out to be that I was accidentally encoding the parameters into the URL instead of passing them in the body. So if you're running into a problem there, there is definitely a very small limit on the size of POST data you can send encoded into the URL.

R - " missing value where TRUE/FALSE needed "

Can you change the if condition to this:

if (!is.na(comments[l])) print(comments[l]);

You can only check for NA values with is.na().

Show a child form in the centre of Parent form in C#

If any windows form(child form) is been opened from a new thread of Main window(parent form) then its not possible to hold the sub window to the center of main window hence we need to fix the position of the sub window manually by means of X and Y co-ordinates.

In the properties of Subwindow change the "StartPosition" to be "Manual"

code in main window

private void SomeFunction()
{
    Thread m_Thread = new Thread(LoadingUIForm);
    m_Thread.Start();
    OtherParallelFunction();
    m_Thread.Abort();
}

private void LoadingUIForm()
{
    m_LoadingWindow = new LoadingForm(this);
    m_LoadingWindow.ShowDialog();
}

code in subwindow for defining its own position by means of parent current position as well as size

public LoadingForm(Control m_Parent)
{
   InitializeComponent();
   this.Location = new Point( m_Parent.Location.X+(m_Parent.Size.Width/2)-(this.Size.Width/2),
                              m_Parent.Location.Y+(m_Parent.Size.Height/2)-(this.Size.Height/2)
                            );
}

Here the co-ordinates of center of parent is calculated as well as the subwindow is kept exactly at the center of the parent by calculating its own center by (this.height/2) and (this.width/2) this function can be further taken for parent relocated events also.

PHP How to fix Notice: Undefined variable:

Declare them before the while loop.

$hn = "";
$pid = "";
$datereg = "";
$prefix = "";
$fname = "";
$lname = "";
$age = "";
$sex = "";

You are getting the notice because the variables are declared and assigned inside the loop.

Renaming the current file in Vim

There's a sightly larger plugin called vim-eunuch by Tim Pope that includes a rename function as well as some other goodies (delete, find, save all, chmod, sudo edit, ...).

To rename a file in vim-eunuch:

:Move filename.ext

Compared to rename.vim:

:rename[!] filename.ext

Saves a few keystrokes :)

How to implement a Navbar Dropdown Hover in Bootstrap v4?

_x000D_
_x000D_
$('body').on('mouseenter mouseleave','.dropdown',function(e){_x000D_
  var _d=$(e.target).closest('.dropdown');_x000D_
  if (e.type === 'mouseenter')_d.addClass('show');_x000D_
  setTimeout(function(){_x000D_
    _d.toggleClass('show', _d.is(':hover'));_x000D_
    $('[data-toggle="dropdown"]', _d).attr('aria-expanded',_d.is(':hover'));_x000D_
  },300);_x000D_
});_x000D_
_x000D_
/* this is not needed, just prevents page reload when a dd link is clicked */_x000D_
$('.dropdown a').on('click tap', e => e.preventDefault())
_x000D_
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet"/>_x000D_
<script src="https://code.jquery.com/jquery-3.1.1.slim.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>_x000D_
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>_x000D_
_x000D_
<nav class="navbar navbar-toggleable-md navbar-light bg-faded">_x000D_
  <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">_x000D_
    <span class="navbar-toggler-icon"></span>_x000D_
  </button>_x000D_
  <a class="navbar-brand" href>Navbar</a>_x000D_
  <div class="collapse navbar-collapse" id="navbarNavDropdown">_x000D_
    <ul class="navbar-nav">_x000D_
      <li class="nav-item active">_x000D_
        <a class="nav-link" href>Home <span class="sr-only">(current)</span></a>_x000D_
      </li>_x000D_
      <li class="nav-item">_x000D_
        <a class="nav-link" href>Features</a>_x000D_
      </li>_x000D_
      <li class="nav-item">_x000D_
        <a class="nav-link" href>Pricing</a>_x000D_
      </li>_x000D_
      <li class="nav-item dropdown">_x000D_
        <a class="nav-link dropdown-toggle" href id="navbarDropdownMenuLink" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">_x000D_
          Dropdown link_x000D_
        </a>_x000D_
        <div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">_x000D_
          <a class="dropdown-item" href>Action</a>_x000D_
          <a class="dropdown-item" href>Another action</a>_x000D_
          <a class="dropdown-item" href>Something else here</a>_x000D_
        </div>_x000D_
      </li>_x000D_
    </ul>_x000D_
  </div>_x000D_
</nav>
_x000D_
_x000D_
_x000D_

Why does Date.parse give incorrect results?

Another solution is to build an associative array with date format and then reformat data.

This method is useful for date formatted in an unussual way.

An example:

    mydate='01.02.12 10:20:43':
    myformat='dd/mm/yy HH:MM:ss';


    dtsplit=mydate.split(/[\/ .:]/);
    dfsplit=myformat.split(/[\/ .:]/);

    // creates assoc array for date
    df = new Array();
    for(dc=0;dc<6;dc++) {
            df[dfsplit[dc]]=dtsplit[dc];
            }

    // uses assc array for standard mysql format
    dstring[r] = '20'+df['yy']+'-'+df['mm']+'-'+df['dd'];
    dstring[r] += ' '+df['HH']+':'+df['MM']+':'+df['ss'];

IOError: [Errno 13] Permission denied

IOError: [Errno 13] Permission denied: 'juliodantas2015.json'

tells you everything you need to know: though you successfully made your python program executable with your chmod, python can't open that juliodantas2015.json' file for writing. You probably don't have the rights to create new files in the folder you're currently in.

How to fix warning from date() in PHP"

You could also use this:

ini_alter('date.timezone','Asia/Calcutta');

You should call this before calling any date function. It accepts the key as the first parameter to alter PHP settings during runtime and the second parameter is the value.

I had done these things before I figured out this:

  1. Changed the PHP.timezone to "Asia/Calcutta" - but did not work
  2. Changed the lat and long parameters in the ini - did not work
  3. Used date_default_timezone_set("Asia/Calcutta"); - did not work
  4. Used ini_alter() - IT WORKED
  5. Commented date_default_timezone_set("Asia/Calcutta"); - IT WORKED
  6. Reverted the changes made to the PHP.ini - IT WORKED

For me the init_alter() method got it all working.

I am running Apache 2 (pre-installed), PHP 5.3 on OSX mountain lion

How to get equal width of input and select fields

Add this code in css:

 select, input[type="text"]{
      width:100%;
      box-sizing:border-box;
    }

Excel formula to reference 'CELL TO THE LEFT'

Please select the entire sheet and HOME > Styles - Conditional Formatting, New Rule..., Use a formula to determine which cells to format and Format values where this formula is true::

=A1<>XFD1

Format..., select choice of formatting, OK, OK.

Angular 5 ngHide ngShow [hidden] not working

Try this

 <input class="txt" type="password" [(ngModel)]="input_pw" [hidden]="isHidden">

Parse String date in (yyyy-MM-dd) format

DateFormat df = new SimpleDateFormat("MM/dd/yyyy");
String cunvertCurrentDate="06/09/2015";
Date date = new Date();
date = df.parse(cunvertCurrentDate);

<ng-container> vs <template>

Imo use cases for ng-container are simple replacements for which a custom template/component would be overkill. In the API doc they mention the following

use a ng-container to group multiple root nodes

and I guess that's what it is all about: grouping stuff.

Be aware that the ng-container directive falls away instead of a template where its directive wraps the actual content.

How to change the URI (URL) for a remote Git repository?

To check git remote connection:

git remote -v

Now, set the local repository to remote git:

git remote set-url origin https://NewRepoLink.git

Now to make it upstream or push use following code:

git push --set-upstream origin master -f

How can I use LTRIM/RTRIM to search and replace leading/trailing spaces?

To remove spaces... please use LTRIM/RTRIM

 LTRIM(String)
 RTRIM(String)

The String parameter that is passed to the functions can be a column name, a variable, a literal string or the output of a user defined function or scalar query.

SELECT LTRIM(' spaces at start')
SELECT RTRIM(FirstName) FROM Customers

Read more: http://rockingshani.blogspot.com/p/sq.html#ixzz33SrLQ4Wi

How to import and use image in a Vue single file component?

These both work for me in JavaScript and TypeScript

<img src="@/assets/images/logo.png" alt=""> 

or

 <img src="./assets/images/logo.png" alt="">

How to exclude rows that don't join with another table?

Another solution is:

SELECT * FROM TABLE1 WHERE id NOT IN (SELECT id FROM TABLE2)

Creating an empty Pandas DataFrame, then filling it?

Initialize empty frame with column names

import pandas as pd

col_names =  ['A', 'B', 'C']
my_df  = pd.DataFrame(columns = col_names)
my_df

Add a new record to a frame

my_df.loc[len(my_df)] = [2, 4, 5]

You also might want to pass a dictionary:

my_dic = {'A':2, 'B':4, 'C':5}
my_df.loc[len(my_df)] = my_dic 

Append another frame to your existing frame

col_names =  ['A', 'B', 'C']
my_df2  = pd.DataFrame(columns = col_names)
my_df = my_df.append(my_df2)

Performance considerations

If you are adding rows inside a loop consider performance issues. For around the first 1000 records "my_df.loc" performance is better, but it gradually becomes slower by increasing the number of records in the loop.

If you plan to do thins inside a big loop (say 10M? records or so), you are better off using a mixture of these two; fill a dataframe with iloc until the size gets around 1000, then append it to the original dataframe, and empty the temp dataframe. This would boost your performance by around 10 times.

"Initializing" variables in python?

The issue is in the line -

grade_1, grade_2, grade_3, average = 0.0

and

fName, lName, ID, converted_ID = ""

In python, if the left hand side of the assignment operator has multiple variables, python would try to iterate the right hand side that many times and assign each iterated value to each variable sequentially. The variables grade_1, grade_2, grade_3, average need three 0.0 values to assign to each variable.

You may need something like -

grade_1, grade_2, grade_3, average = [0.0 for _ in range(4)]
fName, lName, ID, converted_ID = ["" for _ in range(4)]

Access-Control-Allow-Origin wildcard subdomains, ports and protocols

We were having similar issues with Font Awesome on a static "cookie-less" domain when reading fonts from the "cookie domain" (www.domain.tld) and this post was our hero. See here: How can I fix the 'Missing Cross-Origin Resource Sharing (CORS) Response Header' webfont issue?

For the copy/paste-r types (and to give some props) I pieced this together from all the contributions and added it to the top of the .htaccess file of the site root:

<IfModule mod_headers.c>
 <IfModule mod_rewrite.c>
    SetEnvIf Origin "http(s)?://(.+\.)?(othersite\.com|mywebsite\.com)(:\d{1,5})?$" CORS=$0
    Header set Access-Control-Allow-Origin "%{CORS}e" env=CORS
    Header merge  Vary "Origin"
 </IfModule>
</IfModule>

Super Secure, Super Elegant. Love it: You don't have to open up your servers bandwidth to resource thieves / hot-link-er types.

Props to:@Noyo @DaveRandom @pratap-koritala

(I tried to leave this as a comment to the accepted answer, but I can't do that yet)

HTML5 Canvas vs. SVG vs. div

To add to this, I've been doing a diagram application, and initially started out with canvas. The diagram consists of many nodes, and they can get quite big. The user can drag elements in the diagram around.

What I found was that on my Mac, for very large images, SVG is superior. I have a MacBook Pro 2013 13" Retina, and it runs the fiddle below quite well. The image is 6000x6000 pixels, and has 1000 objects. A similar construction in canvas was impossible to animate for me when the user was dragging objects around in the diagram.

On modern displays you also have to account for different resolutions, and here SVG gives you all of this for free.

Fiddle: http://jsfiddle.net/knutsi/PUcr8/16/

Fullscreen: http://jsfiddle.net/knutsi/PUcr8/16/embedded/result/

var wiggle_factor = 0.0;
nodes = [];

// create svg:
var svg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
svg.setAttribute('style', 'border: 1px solid black');
svg.setAttribute('width', '6000');
svg.setAttribute('height', '6000');

svg.setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:xlink",
    "http://www.w3.org/1999/xlink");

document.body.appendChild(svg);


function makeNode(wiggle) {
    var node = document.createElementNS("http://www.w3.org/2000/svg", "g");
    var node_x = (Math.random() * 6000);
    var node_y = (Math.random() * 6000);
    node.setAttribute("transform", "translate(" + node_x + ", " + node_y +")");

    // circle:
    var circ = document.createElementNS("http://www.w3.org/2000/svg", "circle");
    circ.setAttribute( "id","cir")
    circ.setAttribute( "cx", 0 + "px")
    circ.setAttribute( "cy", 0 + "px")
    circ.setAttribute( "r","100px");
    circ.setAttribute('fill', 'red');
    circ.setAttribute('pointer-events', 'inherit')

    // text:
    var text = document.createElementNS("http://www.w3.org/2000/svg", "text");
    text.textContent = "This is a test! ÅÆØ";

    node.appendChild(circ);
    node.appendChild(text);

    node.x = node_x;
    node.y = node_y;

    if(wiggle)
        nodes.push(node)
    return node;
}

// populate with 1000 nodes:
for(var i = 0; i < 1000; i++) {
    var node = makeNode(true);
    svg.appendChild(node);
}

// make one mapped to mouse:
var bnode = makeNode(false);
svg.appendChild(bnode);

document.body.onmousemove=function(event){
    bnode.setAttribute("transform","translate(" +
        (event.clientX + window.pageXOffset) + ", " +
        (event.clientY + window.pageYOffset) +")");
};

setInterval(function() {
    wiggle_factor += 1/60;
    nodes.forEach(function(node) {

        node.setAttribute("transform", "translate(" 
                          + (Math.sin(wiggle_factor) * 200 + node.x) 
                          + ", " 
                          + (Math.sin(wiggle_factor) * 200 + node.y) 
                          + ")");        
    })
},1000/60);

postgresql - add boolean column to table set default

In psql alter column query syntax like this

Alter table users add column priv_user boolean default false ;

boolean value (true-false) save in DB like (t-f) value .

How to concatenate strings in django templates?

In my project I did it like this:

@register.simple_tag()
def format_string(string: str, *args: str) -> str:
    """
    Adds [args] values to [string]
    String format [string]: "Drew %s dad's %s dead."
    Function call in template: {% format_string string "Dodd's" "dog's" %}
    Result: "Drew Dodd's dad's dog's dead."
    """
    return string % args

Here, the string you want concatenate and the args can come from the view, for example.

In template and using your case:

{% format_string 'shop/%s/base.html' shop_name as template %}
{% include template %}

The nice part is that format_string can be reused for any type of string formatting in templates

Tomcat 7 "SEVERE: A child container failed during start"

for me one case was I just missed to maven update project which caused the same issue

maven update project and try if you see any errors in POM.xml

Creating random colour in Java?

Here is a method for getting a random color:

private static Random sRandom;

public static synchronized int randomColor() {
    if (sRandom == null) {
        sRandom = new Random();
    }
    return 0xff000000 + 256 * 256 * sRandom.nextInt(256) + 256 * sRandom.nextInt(256)
            + sRandom.nextInt(256);
}

Benefits:

  • Get the integer representation which can be used with java.awt.Color or android.graphics.Color
  • Keep a static reference to Random.

Create a temporary table in a SELECT statement without a separate CREATE TABLE

CREATE TEMPORARY TABLE IF NOT EXISTS table2 AS (SELECT * FROM table1)

From the manual found at http://dev.mysql.com/doc/refman/5.7/en/create-table.html

You can use the TEMPORARY keyword when creating a table. A TEMPORARY table is visible only to the current session, and is dropped automatically when the session is closed. This means that two different sessions can use the same temporary table name without conflicting with each other or with an existing non-TEMPORARY table of the same name. (The existing table is hidden until the temporary table is dropped.) To create temporary tables, you must have the CREATE TEMPORARY TABLES privilege.

RHEL 6 - how to install 'GLIBC_2.14' or 'GLIBC_2.15'?

This often occurs when you build software in RHEL 7 and try to run on RHEL 6.

To update GLIBC to any version, simply download the package from

https://ftp.gnu.org/gnu/libc/

For example glibc-2.14.tar.gz in your case.

1. tar xvfz glibc-2.14.tar.gz
2. cd glibc-2.14
3. mkdir build
4. cd build
5. ../configure --prefix=/opt/glibc-2.14
6. make
7. sudo make install
8. export LD_LIBRARY_PATH=/opt/glibc-2.14/lib:$LD_LIBRARY_PATH

Then try to run your software, glibc-2.14 should be linked.

Android difference between Two Dates

Here is the modern answer. It’s good for anyone who either uses Java 8 or later (which doesn’t go for most Android phones yet) or is happy with an external library.

    String date1 = "20170717141000";
    String date2 = "20170719175500";

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
    Duration diff = Duration.between(LocalDateTime.parse(date1, formatter), 
                                     LocalDateTime.parse(date2, formatter));

    if (diff.isZero()) {
        System.out.println("0m");
    } else {
        long days = diff.toDays();
        if (days != 0) {
            System.out.print("" + days + "d ");
            diff = diff.minusDays(days);
        }
        long hours = diff.toHours();
        if (hours != 0) {
            System.out.print("" + hours + "h ");
            diff = diff.minusHours(hours);
        }
        long minutes = diff.toMinutes();
        if (minutes != 0) {
            System.out.print("" + minutes + "m ");
            diff = diff.minusMinutes(minutes);
        }
        long seconds = diff.getSeconds();
        if (seconds != 0) {
            System.out.print("" + seconds + "s ");
        }
        System.out.println();
    }

This prints

2d 3h 45m 

In my own opinion the advantage is not so much that it is shorter (it’s not much), but leaving the calculations to an standard library is less errorprone and gives you clearer code. These are great advantages. The reader is not burdened with recognizing constants like 24, 60 and 1000 and verifying that they are used correctly.

I am using the modern Java date & time API (described in JSR-310 and also known under this name). To use this on Android under API level 26, get the ThreeTenABP, see this question: How to use ThreeTenABP in Android Project. To use it with other Java 6 or 7, get ThreeTen Backport. With Java 8 and later it is built-in.

With Java 9 it will be still a bit easier since the Duration class is extended with methods to give you the days part, hours part, minutes part and seconds part separately so you don’t need the subtractions. See an example in my answer here.

How to call a MySQL stored procedure from within PHP code?

This is my solution with prepared statements and stored procedure is returning several rows not only one value.

<?php

require 'config.php';
header('Content-type:application/json');
$connection->set_charset('utf8');

$mIds = $_GET['ids'];

$stmt = $connection->prepare("CALL sp_takes_string_returns_table(?)");
$stmt->bind_param("s", $mIds);

$stmt->execute();

$result = $stmt->get_result();
$response = $result->fetch_all(MYSQLI_ASSOC);
echo json_encode($response);

$stmt->close();
$connection->close();

Greater than less than, python

Check to make sure that both score and array[x] are numerical types. You might be comparing an integer to a string...which is heartbreakingly possible in Python 2.x.

>>> 2 < "2"
True
>>> 2 > "2"
False
>>> 2 == "2"
False

Edit

Further explanation: How does Python compare string and int?

The provider is not compatible with the version of Oracle client

This issue could by happen while using unmanaged oracle reference if you have more than one oracle client , or sometimes if you reference different version
There is two way to solve it :

  1. First and fast solution is to remove unmanaged reference and use the managed one from NuGet see this before to go with this option Differences between the ODP.NET Managed Driver and Unmanaged Driver

  2. Second solution is to fix project unmanaged target version like the below :

  • First Check oracle project reference version (from project references/(dependencies > assemblies ) > Oracle.DataAccess right click > properties):

    enter image description here

    enter image description here

Then check oracle GAC version

  • got to gac from run (Win+R) "%windir%\Microsoft.NET\assembly"
    enter image description here

  • Check the platform that matches with you project platform

    enter image description here

  • to check you target platform (right click on your project > properties)

    enter image description here

  • From gac folder search to Oracle.DataAccess

    enter image description here

  • Right Click on Oracle.DataAccess > properties > details and check version

    enter image description here

  • if you notice the versions are different this is an the issue and to fix it we need to redirect assembly version (in startup project go to config file and add the below section )

<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Oracle.DataAccess" publicKeyToken="89b483f429c47342" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.0.0.0" newVersion="4.121.2.0" />
      </dependentAssembly>
</assemblyBinding>

like this enter image description here

oldVersion : should be cover your project version newVersion : GAC version publicKeyToken : From GAC

enter image description here

How to recover Git objects damaged by hard disk failure?

In some previous backups, your bad objects may have been packed in different files or may be loose objects yet. So your objects may be recovered.

It seems there are a few bad objects in your database. So you could do it the manual way.

Because of git hash-object, git mktree and git commit-tree do not write the objects because they are found in the pack, then start doing this:

mv .git/objects/pack/* <somewhere>
for i in <somewhere>/*.pack; do
  git unpack-objects -r < $i
done
rm <somewhere>/*

(Your packs are moved out from the repository, and unpacked again in it; only the good objects are now in the database)

You can do:

git cat-file -t 6c8cae4994b5ec7891ccb1527d30634997a978ee

and check the type of the object.

If the type is blob: retrieve the contents of the file from previous backups (with git show or git cat-file or git unpack-file; then you may git hash-object -w to rewrite the object in your current repository.

If the type is tree: you could use git ls-tree to recover the tree from previous backups; then git mktree to write it again in your current repository.

If the type is commit: the same with git show, git cat-file and git commit-tree.

Of course, I would backup your original working copy before starting this process.

Also, take a look at How to Recover Corrupted Blob Object.

How to detect a mobile device with JavaScript?

I advise you check out http://wurfl.io/

In a nutshell, if you import a tiny JS file:

<script type='text/javascript' src="//wurfl.io/wurfl.js"></script>

you will be left with a JSON object that looks like:

{
 "complete_device_name":"Google Nexus 7",
 "is_mobile":true,
 "form_factor":"Tablet"
}

(that's assuming you are using a Nexus 7, of course) and you will be able to do things like:

WURFL.complete_device_name

This is what you are looking for.

Disclaimer: I work for the company that offers this free service. Thanks.

Scraping: SSL: CERTIFICATE_VERIFY_FAILED error for http://en.wikipedia.org

Use requests library. Try this solution, or just add https:// before the URL:

import requests
from bs4 import BeautifulSoup
import re

pages = set()
def getLinks(pageUrl):
    global pages
    html = requests.get("http://en.wikipedia.org"+pageUrl, verify=False).text
    bsObj = BeautifulSoup(html)
    for link in bsObj.findAll("a", href=re.compile("^(/wiki/)")):
        if 'href' in link.attrs:
            if link.attrs['href'] not in pages:
                #We have encountered a new page
                newPage = link.attrs['href']
                print(newPage)
                pages.add(newPage)
                getLinks(newPage)
getLinks("")

Check if this works for you

How to use if statements in underscore.js templates?

If you prefer shorter if else statement, you can use this shorthand:

<%= typeof(id)!== 'undefined' ?  id : '' %>

It means display the id if is valid and blank if it wasn't.

CSS3 Transition not working

Transition is more like an animation.

div.sicon a {
    background:-moz-radial-gradient(left, #ffffff 24%, #cba334 88%);
    transition: background 0.5s linear;
    -moz-transition: background 0.5s linear; /* Firefox 4 */
    -webkit-transition: background 0.5s linear; /* Safari and Chrome */
    -o-transition: background 0.5s linear; /* Opera */
    -ms-transition: background 0.5s linear; /* Explorer 10 */
}

So you need to invoke that animation with an action.

div.sicon a:hover {
    background:-moz-radial-gradient(left, #cba334 24%, #ffffff 88%);
}

Also check for browser support and if you still have some problem with whatever you're trying to do! Check css-overrides in your stylesheet and also check out for behavior: ***.htc css hacks.. there may be something overriding your transition!

You should check this out: http://www.w3schools.com/css/css3_transitions.asp

Hive Alter table change Column Name

Change Column Name/Type/Position/Comment:

ALTER TABLE table_name CHANGE [COLUMN] col_old_name col_new_name column_type [COMMENT col_comment] [FIRST|AFTER column_name]

Example:

CREATE TABLE test_change (a int, b int, c int);

// will change column a's name to a1
ALTER TABLE test_change CHANGE a a1 INT;

Find the last time table was updated

Find last time of update on a table

SELECT
tbl.name
,ius.last_user_update
,ius.user_updates
,ius.last_user_seek
,ius.last_user_scan
,ius.last_user_lookup
,ius.user_seeks
,ius.user_scans
,ius.user_lookups
FROM
sys.dm_db_index_usage_stats ius INNER JOIN
sys.tables tbl ON (tbl.OBJECT_ID = ius.OBJECT_ID)
WHERE ius.database_id = DB_ID()

http://www.sqlserver-dba.com/2012/10/sql-server-find-last-time-of-update-on-a-table.html

"Series objects are mutable and cannot be hashed" error

Shortly: gene_name[x] is a mutable object so it cannot be hashed. To use an object as a key in a dictionary, python needs to use its hash value, and that's why you get an error.

Further explanation:

Mutable objects are objects which value can be changed. For example, list is a mutable object, since you can append to it. int is an immutable object, because you can't change it. When you do:

a = 5;
a = 3;

You don't change the value of a, you create a new object and make a point to its value.

Mutable objects cannot be hashed. See this answer.

To solve your problem, you should use immutable objects as keys in your dictionary. For example: tuple, string, int.

How to compare variables to undefined, if I don’t know whether they exist?

if (!obj) {
    // object (not class!) doesn't exist yet
}
else ...

Accept server's self-signed ssl certificate in Java client

If 'they' are using a self-signed certificate it is up to them to take the steps required to make their server usable. Specifically that means providing their certificate to you offline in a trustworthy way. So get them to do that. You then import that into your truststore using the keytool as described in the JSSE Reference Guide. Don't even think about the insecure TrustManager posted here.

EDIT For the benefit of the seventeen (!) downvoters, and numerous commenters below, who clearly have not actually read what I have written here, this is not a jeremiad against self-signed certificates. There is nothing wrong with self-signed certificates when implemented correctly. But, the correct way to implement them is to have the certificate delivered securely via an offline process, rather than via the unauthenticated channel they are going to be used to authenticate. Surely this is obvious? It is certainly obvious to every security-aware organization I have ever worked for, from banks with thousands of branches to my own companies. The client-side code-base 'solution' of trusting all certificates, including self-signed certificates signed by absolutely anybody, or any arbitary body setting itself up as a CA, is ipso facto not secure. It is just playing at security. It is pointless. You are having a private, tamperproof, reply-proof, injection-proof conversation with ... somebody. Anybody. A man in the middle. An impersonator. Anybody. You may as well just use plaintext.

How to insert logo with the title of a HTML page?

Yes you right and I just want to make it understandable for complete beginners.

  1. Create favicon.ico file you want to be shown next to your url in browsers tab. You can do that online. I used http://www.prodraw.net/favicon/generator.php it worked juts fine.
  2. Save generated ico file in your web site root directory /images (yourwebsite/images) under the name favicon.ico.
  3. Copy this tag <link rel="shortcut icon" href="images/favicon.ico" /> and past it without any changes in between <head> opening and </head> closing tag.
  4. Save changes in your html file and reload your browser.

javax.net.ssl.SSLException: Read error: ssl=0x9524b800: I/O error during system call, Connection reset by peer

If using Nginx and getting a similar problem, then this might help:

Scan your domain on this sslTesturl, and see if the connection is allowed for your device version.

If lower version devices(like < Android 4.4.2 etc) are not able to connect due to TLS support, then try adding this to your Nginx config file,

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

Python Pip install Error: Unable to find vcvarsall.bat. Tried all solutions

I was getting the same error in python 3.4.3 too and I tried using the solutions mentioned here and elsewhere with no success.

Microsoft makes a compiler available for Python 2.7 but it didn't do me much good since I am on 3.4.3.

Python since 3.3 has transitioned over to 2010 and you can download and install Visual C++ 2010 Express for free here: https://www.visualstudio.com/downloads/download-visual-studio-vs#d-2010-express

Here is the official blog post talking about the transition to 2010 for 3.3: http://blog.python.org/2012/05/recent-windows-changes-in-python-33.html

Because previous versions gave a different error for vcvarsall.bat I would double check the version you are using with "pip -V"

C:\Users\B>pip -V
pip 6.0.8 from C:\Python34\lib\site-packages (python 3.4)

As a side note, I too tried using the latest version of VC++ (2013) first but it required installing 2010 express.

From that point forward it should work for anyone using the 32 bit version, if you are on the 64 bit version you will then get the ValueError: ['path'] message because VC++ 2010 doesn't have a 64 bit compuler. For that you have to get the Microsoft SDK 7.1. I can't hyperlink the instruction for 64 bit because I am limited to 2 links per post but its at

Python PIP has issues with path for MS Visual Studio 2010 Express for 64-bit install on Windows 7

Curl command line for consuming webServices?

Posting a string:

curl -d "String to post" "http://www.example.com/target"

Posting the contents of a file:

curl -d @soap.xml "http://www.example.com/target"

How to match, but not capture, part of a regex?

A variation of the expression by @Gumbo that makes use of \K for resetting match positions to prevent the inclusion of number blocks in the match. Usable in PCRE regex flavours.

123-\K(?:(?:apple|banana)(?=-456)|456\K)

Matches:

Match 1  apple
Match 2  banana
Match 3

Empty ArrayList equals null

arrayList == null if there are no instance of the class ArrayList assigned to the variable arrayList (note the upercase for classes and the lowercase for variables).

If, at anytime, you do arrayList = new ArrayList() then arrayList != null because is pointing to an instance of the class ArrayList

If you want to know if the list is empty, do

if(arrayList != null && !arrayList.isEmpty()) {
 //has items here. The fact that has items does not mean that the items are != null. 
 //You have to check the nullity for every item

}
else {
// either there is no instance of ArrayList in arrayList or the list is empty.
}

If you don't want null items in your list, I'd suggest you to extend the ArrayList class with your own, for example:

public class NotNullArrayList extends ArrayList{

@Override
public boolean add(Object o) 
   { if(o==null) throw new IllegalArgumentException("Cannot add null items to the list");
      else return super.add(o);
    }
}

Or maybe you can extend it to have a method inside your own class that re-defines the concept of "empty List".

public class NullIsEmptyArrayList extends ArrayList{

@Override
public boolean isEmpty() 
   if(super.isEmpty()) return true;
   else{
   //Iterate through the items to see if all of them are null. 
   //You can use any of the algorithms in the other responses. Return true if all are null, false otherwise. 
   //You can short-circuit to return false when you find the first item not null, so it will improve performance.
  }
}

The last two approaches are more Object-Oriented, more elegant and reusable solutions.

Updated with Jeff suggestion IAE instead of NPE.

How to transform currentTimeMillis to a readable date format?

There is a simpler way in Android

 DateFormat.getInstance().format(currentTimeMillis);

Moreover, Date is deprecated, so use DateFormat class.

   DateFormat.getDateInstance().format(new Date(0));  
   DateFormat.getDateTimeInstance().format(new Date(0));  
   DateFormat.getTimeInstance().format(new Date(0));  

The above three lines will give:

Dec 31, 1969  
Dec 31, 1969 4:00:00 PM  
4:00:00 PM  12:00:00 AM

Format numbers in django templates

Building on other answers, to extend this to floats, you can do:

{% load humanize %}
{{ floatvalue|floatformat:2|intcomma }}

Documentation: floatformat, intcomma.

Could not resolve placeholder in string value

I got same error in my Micro-service, whenever you declare @Value annotation in program i.e @Value("${project.api.key}")

make sure that your application.properties file with same values should not be blank project.api.key= add some values

MostIMP :otherwise it will throw error "Error creating bean with name 'ServiceFTP': Injection of autowired dependencies"

PDF Blob - Pop up window not showing content

I use AngularJS v1.3.4

HTML:

<button ng-click="downloadPdf()" class="btn btn-primary">download PDF</button>

JS controller:

'use strict';
angular.module('xxxxxxxxApp')
    .controller('MathController', function ($scope, MathServicePDF) {
        $scope.downloadPdf = function () {
            var fileName = "test.pdf";
            var a = document.createElement("a");
            document.body.appendChild(a);
            MathServicePDF.downloadPdf().then(function (result) {
                var file = new Blob([result.data], {type: 'application/pdf'});
                var fileURL = window.URL.createObjectURL(file);
                a.href = fileURL;
                a.download = fileName;
                a.click();
            });
        };
});

JS services:

angular.module('xxxxxxxxApp')
    .factory('MathServicePDF', function ($http) {
        return {
            downloadPdf: function () {
            return $http.get('api/downloadPDF', { responseType: 'arraybuffer' }).then(function (response) {
                return response;
            });
        }
    };
});

Java REST Web Services - Spring MVC:

@RequestMapping(value = "/downloadPDF", method = RequestMethod.GET, produces = "application/pdf")
    public ResponseEntity<byte[]> getPDF() {
        FileInputStream fileStream;
        try {
            fileStream = new FileInputStream(new File("C:\\xxxxx\\xxxxxx\\test.pdf"));
            byte[] contents = IOUtils.toByteArray(fileStream);
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.parseMediaType("application/pdf"));
            String filename = "test.pdf";
            headers.setContentDispositionFormData(filename, filename);
            ResponseEntity<byte[]> response = new ResponseEntity<byte[]>(contents, headers, HttpStatus.OK);
            return response;
        } catch (FileNotFoundException e) {
           System.err.println(e);
        } catch (IOException e) {
            System.err.println(e);
        }
        return null;
    }

How to concatenate two strings in C++?

There is a strcat() function from the ported C library that will do "C style string" concatenation for you.

BTW even though C++ has a bunch of functions to deal with C-style strings, it could be beneficial for you do try and come up with your own function that does that, something like:

char * con(const char * first, const char * second) {
    int l1 = 0, l2 = 0;
    const char * f = first, * l = second;

    // step 1 - find lengths (you can also use strlen)
    while (*f++) ++l1;
    while (*l++) ++l2;

    char *result = new char[l1 + l2];

    // then concatenate
    for (int i = 0; i < l1; i++) result[i] = first[i];
    for (int i = l1; i < l1 + l2; i++) result[i] = second[i - l1];

    // finally, "cap" result with terminating null char
    result[l1+l2] = '\0';
    return result;
}

...and then...

char s1[] = "file_name";
char *c = con(s1, ".txt");

... the result of which is file_name.txt.

You might also be tempted to write your own operator + however IIRC operator overloads with only pointers as arguments is not allowed.

Also, don't forget the result in this case is dynamically allocated, so you might want to call delete on it to avoid memory leaks, or you could modify the function to use stack allocated character array, provided of course it has sufficient length.

Failure during conversion to COFF: file invalid or corrupt

This issue occurred after Visual Studio 2012 installation. The issue resolved by replacing the cvtres.exe from VS2010 with the one from VS2012.

Thank you to "social.msdn"!

How to install gem from GitHub source?

On a fresh Linux machine you also need to install git. Bundle uses it behind the scenes.

How to set the context path of a web application in Tomcat 7.0

It's not recommended to update the server configuration like server.xml or ROOT.xml.

You can put a context.xml configuration file under your web-application META-INF directory, with the context path setting included. This will override the default server setting?

i.e.:

<Context docBase="yourAppName" path="/yourAppPath" reloadable="true">

Connect Android Studio with SVN

Go to File->Settings->Version Control->Subversion enter the path for your SVN executable in the General tab under Subversion configuration directory. Also, you can download a latest SVN client such as VisualSVN and point the path to the executable as mentioned above. That will most likely solve your problem.

How to get the nth element of a python list or a default if not available

(a[n:]+[default])[0]

This is probably better as a gets larger

(a[n:n+1]+[default])[0]

This works because if a[n:] is an empty list if n => len(a)

Here is an example of how this works with range(5)

>>> range(5)[3:4]
[3]
>>> range(5)[4:5]
[4]
>>> range(5)[5:6]
[]
>>> range(5)[6:7]
[]

And the full expression

>>> (range(5)[3:4]+[999])[0]
3
>>> (range(5)[4:5]+[999])[0]
4
>>> (range(5)[5:6]+[999])[0]
999
>>> (range(5)[6:7]+[999])[0]
999

What is tempuri.org?

Probably to guarantee that public webservices will be unique.

It always makes me think of delicious deep fried treats...

Make a negative number positive

Can you please try this one?

public static int toPositive(int number) {
    return number & 0x7fffffff;
}

form with no action and where enter does not reload page

Add an onsubmit handler to the form (either via plain js or jquery $().submit(fn)), and return false unless your specific conditions are met.

Unless you don't want the form to submit, ever - in which case, why not just leave out the 'action' attribute on the form element?

How can I get the active screen dimensions?

I needed to set the maximum size of my window application. This one could changed accordingly the application is is been showed in the primary screen or in the secondary. To overcome this problem e created a simple method that i show you next:

/// <summary>
/// Set the max size of the application window taking into account the current monitor
/// </summary>
public static void SetMaxSizeWindow(ioConnect _receiver)
{
    Point absoluteScreenPos = _receiver.PointToScreen(Mouse.GetPosition(_receiver));

    if (System.Windows.SystemParameters.VirtualScreenLeft == System.Windows.SystemParameters.WorkArea.Left)
    {
        //Primary Monitor is on the Left
        if (absoluteScreenPos.X <= System.Windows.SystemParameters.PrimaryScreenWidth)
        {
            //Primary monitor
            _receiver.WindowApplication.MaxWidth = System.Windows.SystemParameters.WorkArea.Width;
            _receiver.WindowApplication.MaxHeight = System.Windows.SystemParameters.WorkArea.Height;
        }
        else
        {
            //Secondary monitor
            _receiver.WindowApplication.MaxWidth = System.Windows.SystemParameters.VirtualScreenWidth - System.Windows.SystemParameters.WorkArea.Width;
            _receiver.WindowApplication.MaxHeight = System.Windows.SystemParameters.VirtualScreenHeight;
        }
    }

    if (System.Windows.SystemParameters.VirtualScreenLeft < 0)
    {
        //Primary Monitor is on the Right
        if (absoluteScreenPos.X > 0)
        {
            //Primary monitor
            _receiver.WindowApplication.MaxWidth = System.Windows.SystemParameters.WorkArea.Width;
            _receiver.WindowApplication.MaxHeight = System.Windows.SystemParameters.WorkArea.Height;
        }
        else
        {
            //Secondary monitor
            _receiver.WindowApplication.MaxWidth = System.Windows.SystemParameters.VirtualScreenWidth - System.Windows.SystemParameters.WorkArea.Width;
            _receiver.WindowApplication.MaxHeight = System.Windows.SystemParameters.VirtualScreenHeight;
        }
    }
}

How to count down in for loop?

First I recommand you can try use print and observe the action:

for i in range(0, 5, 1):
    print i

the result:

0
1
2
3
4

You can understand the function principle. In fact, range scan range is from 0 to 5-1. It equals 0 <= i < 5

When you really understand for-loop in python, I think its time we get back to business. Let's focus your problem.

You want to use a DECREMENT for-loop in python. I suggest a for-loop tutorial for example.

for i in range(5, 0, -1):
    print i

the result:

5
4
3
2
1

Thus it can be seen, it equals 5 >= i > 0

You want to implement your java code in python:

for (int index = last-1; index >= posn; index--)

It should code this:

for i in range(last-1, posn-1, -1)

SCP Permission denied (publickey). on EC2 only when using -r flag on directories

The -i flag specifies the private key (.pem file) to use. If you don't specify that flag (as in your first command) it will use your default ssh key (usually under ~/.ssh/).

So in your first command, you are actually asking scp to upload the .pem file itself using your default ssh key. I don't think that is what you want.

Try instead with:

scp -r -i /Applications/XAMPP/htdocs/keypairfile.pem uploads/* ec2-user@publicdns:/var/www/html/uploads

Checking letter case (Upper/Lower) within a string in Java

I have streamlined the answer of @Quirliom above into functions that can be used:

private static boolean hasLength(CharSequence data) {
    if (String.valueOf(data).length() >= 8) return true;
    else return false;
}

private static boolean hasSymbol(CharSequence data) {
    String password = String.valueOf(data);
    boolean hasSpecial = !password.matches("[A-Za-z0-9 ]*");
    return hasSpecial;
}

private static boolean hasUpperCase(CharSequence data) {
    String password = String.valueOf(data);
    boolean hasUppercase = !password.equals(password.toLowerCase());
    return hasUppercase;
}

private static boolean hasLowerCase(CharSequence data) {
    String password = String.valueOf(data);
    boolean hasLowercase = !password.equals(password.toUpperCase());
    return hasLowercase;
}

How do I create a Python function with optional arguments?

Try calling it like: obj.some_function( '1', 2, '3', g="foo", h="bar" ). After the required positional arguments, you can specify specific optional arguments by name.

Regular Expression Match to test for a valid year

Building on @r92 answer, for years 1970-2019:

(19[789]\d|20[01]\d)

Error : Index was outside the bounds of the array.

You have declared an array that can store 8 elements not 9.

this.posStatus = new int[8]; 

It means postStatus will contain 8 elements from index 0 to 7.

How to list imported modules?

It's actually working quite good with:

import sys
mods = [m.__name__ for m in sys.modules.values() if m]

This will create a list with importable module names.

Unnamed/anonymous namespaces vs. static functions

From experience I'll just note that while it is the C++ way to put formerly-static functions into the anonymous namespace, older compilers can sometimes have problems with this. I currently work with a few compilers for our target platforms, and the more modern Linux compiler is fine with placing functions into the anonymous namespace.

But an older compiler running on Solaris, which we are wed to until an unspecified future release, will sometimes accept it, and other times flag it as an error. The error is not what worries me, it's what it might be doing when it accepts it. So until we go modern across the board, we are still using static (usually class-scoped) functions where we'd prefer the anonymous namespace.

C++ cout hex values?

There are different kinds of flags & masks you can use as well. Please refer http://www.cplusplus.com/reference/iostream/ios_base/setf/ for more information.

#include <iostream>
using namespace std;

int main()
{
    int num = 255;
    cout.setf(ios::hex, ios::basefield);
    cout << "Hex: " << num << endl;

    cout.unsetf(ios::hex);
    cout << "Original format: " << num << endl;

    return 0;
}

How to check a string starts with numeric number?

See the isDigit(char ch) method:

https://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Character.html

and pass it to the first character of the String using the String.charAt() method.

Character.isDigit(myString.charAt(0));

How to move an entire div element up x pixels?

you can also do this

margin-top:-30px; 
min-height:40px;

this "help" to stop the div yanking everything up a bit.

Changing SqlConnection timeout

Old post but as it comes up for what I was searching for I thought I'd add some information to this topic. I was going to add a comment but I don't have enough rep.

As others have said:

connection.ConnectionTimeout is used for the initial connection

command.CommandTimeout is used for individual searches, updates, etc.

But:

connection.ConnectionTimeout is also used for committing and rolling back transactions.

Yes, this is an absolutely insane design decision.

So, if you are running into a timeout on commit or rollback you'll need to increase this value through the connection string.

How to append contents of multiple files into one file

If the original file contains non-printable characters, they will be lost when using the cat command. Using 'cat -v', the non-printables will be converted to visible character strings, but the output file would still not contain the actual non-printables characters in the original file. With a small number of files, an alternative might be to open the first file in an editor (e.g. vim) that handles non-printing characters. Then maneuver to the bottom of the file and enter ":r second_file_name". That will pull in the second file, including non-printing characters. The same could be done for additional files. When all files have been read in, enter ":w". The end result is that the first file will now contain what it did originally, plus the content of the files that were read in.

What is the best free SQL GUI for Linux for various DBMS systems

For Oracle, I highly recommend the free Oracle SQL Developer

http://www.oracle.com/technology/products/database/sql_developer/index.html

The doucmentation states it also works with non-oracle databases - i've never tried that feature myself, but I do know that it works really well with Oracle

Changing the Status Bar Color for specific ViewControllers using Swift in iOS8

Implement preferredStatusBarStyle as you mentioned and call self.setNeedsStatusBarAppearanceUpdate() in ViewDidLoad and also in Info.plist set UIViewControllerBasedStatusBarAppearance to YES (It's YES by default)

It is not clear why it is not working.I need to check code.One other suggestion is go with working code in viewDidLoad UIApplication.sharedApplication().statusBarStyle = .LightContent and change this to default when you view get disappeared viewWillDisappear.

Python loop to run for certain amount of seconds

Try this:

import time

t_end = time.time() + 60 * 15
while time.time() < t_end:
    # do whatever you do

This will run for 15 min x 60 s = 900 seconds.

Function time.time returns the current time in seconds since 1st Jan 1970. The value is in floating point, so you can even use it with sub-second precision. In the beginning the value t_end is calculated to be "now" + 15 minutes. The loop will run until the current time exceeds this preset ending time.

SQL Greater than, Equal to AND Less Than

Somthing like this should workL

SELECT BookingId, StartTime
FROM Booking
WHERE StartTime between dateadd(hour, -1, getdate()) and getdate()

How to remove array element in mongodb?

This below code will remove the complete object element from the array, where the phone number is '+1786543589455'

db.collection.update(
  { _id: id },
  { $pull: { 'contact': { number: '+1786543589455' } } }
);

Excel - Button to go to a certain sheet

In Excel 2007, goto Insert/Shape and pick a shape. Colour it and enter whatever text you want. Then right click on the shape and insert a hyperlink

enter image description here

enter image description here

A few tips with shapes..

If you want to easily position the shape with cells, hold down Alt when you move the shape and it will lock to the cell. If you don't want the shape to move or resize with rows/columns, right click the shape, select size and properties and choose the setting which works best.

Removing cordova plugins from the project

Scripts based on processing the list of installed plugins may not work as there are dependencies between installed plugins (e,g, cordova-plugin-file and cordova-plugin-file-transfer).

In the example, the script will find the file plugin first, then it will try to remove it and we'll get an error as file-transfer requires it. Therefore, we shall have

php var_dump() vs print_r()

With large arrays, print_r can show far more information than is useful. You can truncate it like this, showing the first 2000 characters or however many you need.

  echo "<pre>" . substr(print_r($dataset, 1), 0, 2000) . "</pre>";

Where is the php.ini file on a Linux/CentOS PC?

On most installs you can find it here:

/etc/php.ini

MSVCP120d.dll missing

I have the same problem with you when I implement OpenCV 2.4.11 on VS 2015. I tried to solve this problem by three methods one by one but they didn't work:

  1. download MSVCP120.DLL online and add it to windows path and OpenCV bin file path
  2. install Visual C++ Redistributable Packages for Visual Studio 2013 both x86 and x86
  3. adjust Debug mode. Go to configuration > C/C++ > Code Generation > Runtime Library and select Multi-threaded Debug (/MTd)

Finally I solved this problem by reinstalling VS2015 with selecting all the options that can be installed, it takes a lot space but it really works.

What is the difference between a static and a non-static initialization code block

You will not write code into a static block that needs to be invoked anywhere in your program. If the purpose of the code is to be invoked then you must place it in a method.

You can write static initializer blocks to initialize static variables when the class is loaded but this code can be more complex..

A static initializer block looks like a method with no name, no arguments, and no return type. Since you never call it it doesn't need a name. The only time its called is when the virtual machine loads the class.

What causes a SIGSEGV

segmentation fault arrives when you access memory which is not declared by the program. You can do this through pointers i.e through memory addresses. Or this may also be due to stackoverflow for eg:

void rec_func() {int q = 5; rec_func();}

int main() {rec_func();}

This call will keep on consuming stack memory until it's completely filled and thus finally stackoverflow happens. Note: it might not be visible in some competitive questions as it leads to timeouterror first but for those in which timeout doesn't happens its a hard time figuring out sigsemv.

cannot convert 'std::basic_string<char>' to 'const char*' for argument '1' to 'int system(const char*)'

try using concatenation of string

Statistics(string date)
    {
        this->date += date;
    }

acually this was a part of a class..

git pull aborted with error filename too long

Solution1 - set global config, by running this command:

git config --system core.longpaths true

Solution2 - or you can edit directly your specific git config file like below:

YourRepoFolder -> .git -> config:

[core]
    repositoryformatversion = 0
    filemode = false
    ...
    longpaths = true        <-- (add this line under core section)

Solution3 - when cloning a new repository: here.

Get the cartesian product of a series of lists?

itertools.product

Available from Python 2.6.

import itertools

somelists = [
   [1, 2, 3],
   ['a', 'b'],
   [4, 5]
]
for element in itertools.product(*somelists):
    print(element)

Which is the same as,

for element in itertools.product([1, 2, 3], ['a', 'b'], [4, 5]):
    print(element)

MySQL Daemon Failed to Start - centos 6

Reference here 2.10.2.1 Troubleshooting Problems Starting the MySQL Server.

1.Find the data directory ,it was configured in my.cnf.

[mysqld]
datadir=/var/lib/mysql

2. Check the err file,it log the error message about why mysql server start failed. the name of err file is related with your hostname.

cd /var/lib/mysql
ll
tail (hostname).err

3.If you find some messages like :

InnoDB: Error: log file ./ib_logfile0 is of different size 0 33554432 bytes
InnoDB: than specified in the .cnf file 0 5242880 bytes!
170513 14:25:22 [ERROR] Plugin 'InnoDB' init function returned error.
170513 14:25:22 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
170513 14:25:22 [ERROR] Unknown/unsupported storage engine: InnoDB
170513 14:25:22 [ERROR] Aborting

then

delete ib_logfile0 and ib_logfile1

, then,

/etc/init.d/mysqld start

Locating child nodes of WebElements in selenium

I also found myself in a similar position a couple of weeks ago. You can also do this by creating a custom ElementLocatorFactory (or simply passing in divA into the DefaultElementLocatorFactory) to see if it's a child of the first div - you would then call the appropriate PageFactory initElements method.

In this case if you did the following:

PageFactory.initElements(new DefaultElementLocatorFactory(divA), pageObjectInstance));
// The Page Object instance would then need a WebElement 
// annotated with something like the xpath above or @FindBy(tagName = "input")

tr:hover not working

Use !important:

.list1 tr:hover{
    background:#fefefe !important;
}

Easiest way to use SVG in Android?

UPDATE: DO NOT use this old answer, better use this: https://stackoverflow.com/a/39266840/4031815

Ok after some hours of research I found svg-android to be quite easy to use, so I'm leaving here step by step instructions:

  1. download lib from: https://code.google.com/p/svg-android/downloads/list Latest version at the moment of writing this is: svg-android-1.1.jar

  2. Put jar in lib dir.

  3. Save your *.svg file in res/drawable dir (In illustrator is as easy as pressing Save as and select svg)

  4. Code the following in your activity using the svg library:

    ImageView imageView = (ImageView) findViewById(R.id.imgView);
    SVG svg = SVGParser.getSVGFromResource(getResources(), R.drawable.example);
    //The following is needed because of image accelaration in some devices such as samsung
    imageView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    imageView.setImageDrawable(svg.createPictureDrawable());
    



You can reduce boilerplate code like this

Very easy I made a simple class to contain past code and reduce boilerplate code, like this:

import android.app.Activity;
import android.view.View;
import android.widget.ImageView;

import com.larvalabs.svgandroid.SVG;
import com.larvalabs.svgandroid.SVGParser;

public class SvgImage {

    private static ImageView imageView;
    private Activity activity;
    private SVG svg;
    private int xmlLayoutId;
    private int drawableId;


    public SvgImage(Activity activity, int layoutId, int drawableId) {
        imageView = (ImageView) activity.findViewById(layoutId);
        svg = SVGParser.getSVGFromResource(activity.getResources(), drawableId);
        //Needed because of image accelaration in some devices such as samsung
        imageView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        imageView.setImageDrawable(svg.createPictureDrawable());
    }
}

Now I can call it like this in activity:

    SvgImage rainSVG = new SvgImage(MainActivity.this, R.id.rainImageView, R.drawable.rain);
    SvgImage thunderSVG = new SvgImage(MainActivity.this, R.id.thunderImageView, R.drawable.thunder);
    SvgImage oceanSVG = new SvgImage(MainActivity.this, R.id.oceanImageView, R.drawable.ocean);
    SvgImage fireSVG = new SvgImage(MainActivity.this, R.id.fireImageView, R.drawable.fire);
    SvgImage windSVG = new SvgImage(MainActivity.this, R.id.windImageView,R.drawable.wind);
    SvgImage universeSVG = new SvgImage(MainActivity.this, R.id.universeImageView,R.drawable.universe);

Can I use DIV class and ID together in CSS?

Yes, in one single division you can use both but it's not very common. While styling you will call both so it will cause some ambiguity if you don't properly choose "x" and "y". Use # for ID and . for class. And for overall division you will either do separate styling or write: #x .y for styling purposes.

How do I empty an input value with jQuery?

Another way is:

$('#element').attr('value', '');

Rotating a view in Android

Extend the TextView class and override the onDraw() method. Make sure the parent view is large enough to handle the rotated button without clipping it.

@Override
protected void onDraw(Canvas canvas) {
     canvas.save();
     canvas.rotate(45,<appropriate x pivot value>,<appropriate y pivot value>);
     super.onDraw(canvas);
     canvas.restore();

} 

Share link on Google+

As of July 25, 2011, the answer is no.

I have looked through their Javascript and it seems they don't want anyone directly accessing their api for +1 at the moment.

The Javascript that does all of the work for the +1 button is here:

https://apis.google.com/js/plusone.js

If you run it through a Javascript cleanup program you can tell that they have obfuscated their code with various functions that only start with letters and constantly refer back to themselves and do cryptic things.

I figure in the next couple of weeks or moths they will release a link based sharing api due to the fact that we will need this for sharing from flash and other web based formats that don't rely on pure html and js.

Rounding Bigdecimal values with 2 Decimal Places

Add 0.001 first to the number and then call setScale(2, RoundingMode.ROUND_HALF_UP)

Code example:

public static void main(String[] args) {
    BigDecimal a = new BigDecimal("10.12445").add(new BigDecimal("0.001"));
    BigDecimal b = a.setScale(2, BigDecimal.ROUND_HALF_UP);
    System.out.println(b);
}

Reload chart data via JSON with Highcharts

Actually maybe you should choose the function update is better.
Here's the document of function update http://api.highcharts.com/highcharts#Series.update

You can just type code like below:

chart.series[0].update({data: [1,2,3,4,5]})

These code will merge the origin option, and update the changed data.

How to remove all white space from the beginning or end of a string?

String.Trim() returns a string which equals the input string with all white-spaces trimmed from start and end:

"   A String   ".Trim() -> "A String"

String.TrimStart() returns a string with white-spaces trimmed from the start:

"   A String   ".TrimStart() -> "A String   "

String.TrimEnd() returns a string with white-spaces trimmed from the end:

"   A String   ".TrimEnd() -> "   A String"

None of the methods modify the original string object.

(In some implementations at least, if there are no white-spaces to be trimmed, you get back the same string object you started with:

csharp> string a = "a"; csharp> string trimmed = a.Trim(); csharp> (object) a == (object) trimmed; returns true

I don't know whether this is guaranteed by the language.)

How to set commands output as a variable in a batch file

These answers were all so close to the answer that I needed. This is an attempt to expand on them.

In a Batch file

If you're running from within a .bat file and you want a single line that allows you to export a complicated command like jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json to a variable named AWS_ACCESS_KEY then you want this:

FOR /F "tokens=* USEBACKQ" %%g IN (`jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json`) do (SET "AWS_ACCESS_KEY=%%g")

On the Command Line

If you're at the C:\ prompt you want a single line that allows you to run a complicated command like jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json to a variable named AWS_ACCESS_KEY then you want this:

FOR /F "tokens=* USEBACKQ" %g IN (`jq -r ".Credentials.AccessKeyId" c:\temp\mfa-getCreds.json`) do (SET "AWS_ACCESS_KEY=%g")

Explanation

The only difference between the two answers above is that on the command line, you use a single % in your variable. In a batch file, you have to double up on the percentage signs (%%).

Since the command includes colons, quotes, and parentheses, you need to include the USEBACKQ line in the options so that you can use backquotes to specify the command to run and then all kinds of funny characters inside of it.

Turning error reporting off php

Read up on the configuration settings (e.g., display_errors, display_startup_errors, log_errors) and update your php.ini or .htaccess or .user.ini file, whichever is appropriate.

It works.

How to use the 'og' (Open Graph) meta tag for Facebook share

I built a tool for meta generation. It pre-configures entries for Facebook, Google+ and Twitter, and you can use it free here: http://www.groovymeta.com

To answer the question a bit more, OG tags (Open Graph) tags work similarly to meta tags, and should be placed in the HEAD section of your HTML file. See Facebook's best practises for more information on how to use OG tags effectively.

JRE installation directory in Windows

Not as a command, but this information is in the registry:

  • Open the key HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment
  • Read the CurrentVersion REG_SZ
  • Open the subkey under Java Runtime Environment named with the CurrentVersion value
  • Read the JavaHome REG_SZ to get the path

For example on my workstation i have

HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment
  CurrentVersion = "1.6"
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.5
  JavaHome = "C:\Program Files\Java\jre1.5.0_20"
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.6
  JavaHome = "C:\Program Files\Java\jre6"

So my current JRE is in C:\Program Files\Java\jre6

Confirm deletion using Bootstrap 3 modal box

You can use Bootbox dialog boxes

$(document).ready(function() {

  $('#btnDelete').click(function() {
    bootbox.confirm("Are you sure want to delete?", function(result) {
      alert("Confirm result: " + result);
    });
  });
});

Plunker Demo

Convert String to System.IO.Stream

To convert a string to a stream you need to decide which encoding the bytes in the stream should have to represent that string - for example you can:

MemoryStream mStrm= new MemoryStream( Encoding.UTF8.GetBytes( contents ) );

MSDN references:

What to return if Spring MVC controller method doesn't return value?

There is nothing wrong with returning a void @ResponseBody and you should for POST requests.

Use HTTP status codes to define errors within exception handler routines instead as others are mentioning success status. A normal method as you have will return a response code of 200 which is what you want, any exception handler can then return an error object and a different code (i.e. 500).

Do you know the Maven profile for mvnrepository.com?

You can put this configuration in your settings.xml file:

            <repository>
                <id>mvnrepository</id>
                <url>http://repo1.maven.org/maven2</url>
                <snapshots>
                    <enabled>false</enabled>
                </snapshots>
                <releases>
                    <enabled>true</enabled>
                </releases>
            </repository>

Why do I get a "permission denied" error while installing a gem?

I wanted to share the steps that I followed that fixed this issue for me in the hopes that it can help someone else (and also as a reminder for me in case something like this happens again)

The issues I'd been having (which were the same as OP's) may have to do with using homebrew to install Ruby.

To fix this, first I updated homebrew:

brew update && brew upgrade
brew doctor

(If brew doctor comes up with any issues, fix them first.) Then I uninstalled ruby

brew uninstall ruby

If rbenv is NOT installed at this point, then

brew install rbenv
brew install ruby-build
echo 'export RBENV_ROOT=/usr/local/var/rbenv' >> ~/.bash_profile
echo 'if which rbenv > /dev/null; then eval "$(rbenv init -)"; fi' >> ~/.bash_profile

Then I used rbenv to install ruby. First, find the desired version:

rbenv install -l

Install that version (e.g. 2.2.2)

rbenv install 2.2.2

Then set the global version to the desired ruby version:

rbenv global 2.2.2

At this point you should see the desired version set for the following commands:

rbenv versions

and

ruby --version

Now you should be able to install bundler:

gem install bundler

And once in the desired project folder, you can install all the required gems:

bundle
bundle install

Python 3: ImportError "No Module named Setuptools"

Your setup.py file needs setuptools. Some Python packages used to use distutils for distribution, but most now use setuptools, a more complete package. Here is a question about the differences between them.

To install setuptools on Debian:

sudo apt-get install python3-setuptools

For an older version of Python (Python 2.x):

sudo apt-get install python-setuptools

How to make a smaller RatingBar?

The Best Answer for small ratingbar

<RatingBar
                    android:layout_width="wrap_content"
                    style = "?android:attr/ratingBarStyleSmall"
                    android:layout_height="wrap_content" />

How to pass extra variables in URL with WordPress

Since this is a frequently visited post i thought to post my solution in case it helps anyone. In WordPress along with using query vars you can change permalinks too like this

www.example.com?c=123 to www.example.com/c/123

For this you have to add these lines of code in functions.php or your plugin base file.

From shankhan's anwer

add_filter( 'query_vars', 'addnew_query_vars', 10, 1 );
function addnew_query_vars($vars)
{   
    $vars[] = 'c'; // c is the name of variable you want to add       
    return $vars;
}

And additionally this snipped to add custom rewriting rules.

function custom_rewrite_basic() 
{
    add_rewrite_rule('^c/([0-9]+)/?', '?c=$1', 'top');
}
add_action('init', 'custom_rewrite_basic');

For the case where you need to add rewrite rules for a specifc page you can use that page slug to write a rewrite rule for that specific page. Like in the question OP has asked about

www.example.com/news?c=123 to www.example.com/news/123

We can change it to the desired behaviour by adding a little modification to our previous function.

function custom_rewrite_basic() 
{
    add_rewrite_rule('^news/([0-9]+)/?', 'news?c=$1', 'top');
}
add_action('init', 'custom_rewrite_basic');

Hoping that it becomes useful for someone.

How to iterate using ngFor loop Map containing key as string and values as map iteration

For Angular 6.1+ , you can use default pipe keyvalue ( Do review and upvote also ) :

<ul>
    <li *ngFor="let recipient of map | keyvalue">
        {{recipient.key}} --> {{recipient.value}}
    </li>
</ul>

WORKING DEMO


For the previous version :

One simple solution to this is convert map to array : Array.from

Component Side :

map = new Map<String, String>();

constructor(){
    this.map.set("sss","sss");
    this.map.set("aaa","sss");
    this.map.set("sass","sss");
    this.map.set("xxx","sss");
    this.map.set("ss","sss");
    this.map.forEach((value: string, key: string) => {
        console.log(key, value);
    });
}

getKeys(map){
    return Array.from(map.keys());
}

Template Side :

<ul>
  <li *ngFor="let recipient of getKeys(map)">
    {{recipient}}
   </li>
</ul>

WORKING DEMO

How to send a simple email from a Windows batch file?

It works for me, by using double quotes around variables.

I am using batch script to call powershell Send-MailMessage

Batch Script:send_email.bat

C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe  -command 'E:\path\send_email.ps1

Pwershell Script send_email.ps1

Send-MailMessage -From "noreply@$env:computername" -To '<[email protected]>' -Subject 'Blah Blah' -SmtpServer  'smtp.domain.com'  -Attachments 'E:\path\file.log' -BODY "Blah Blah on Host: $env:computername "

Warning about SSL connection when connecting to MySQL database

Since I am currently in development mode I set useSSL to No not in tomcat but in mysql server configurations. Went to Manage Access Settings\Manage Server Connections from workbench -> Selected my connection. Inside connection tab went to SSL tab and disabled the settings. Worked for me.

User Get-ADUser to list all properties and export to .csv

This can be simplified by completely skipping the where object and the $users declaration. All you need is:

Code

get-content c:\scripts\users.txt | get-aduser -properties * | select displayname, office | export-csv c:\path\to\your.csv

Cannot connect to the Docker daemon on macOS

I have Mac OS and I open Launchpad and select docker application. from reset tab click on restart.

An existing connection was forcibly closed by the remote host - WCF

The issue I had was also with serialization. The cause was some of my DTO/business classes and properties were renamed or deleted without updating the service reference. I'm surprised I didn't get a contract filter mismatch error instead. But updating the service ref fixed the error for me (same error as OP).

jQuery - select the associated label element of a input field

As long and your input and label elements are associated by their id and for attributes, you should be able to do something like this:

$('.input').each(function() { 
   $this = $(this);
   $label = $('label[for="'+ $this.attr('id') +'"]');
   if ($label.length > 0 ) {
       //this input has a label associated with it, lets do something!
   }
});

If for is not set then the elements have no semantic relation to each other anyway, and there is no benefit to using the label tag in that instance, so hopefully you will always have that relationship defined.

Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)

There are other options for you to benchmark:

1.) A window function will return the actual size directly (tested in MariaDB):

SELECT 
  `mytable`.*,
  COUNT(*) OVER() AS `total_count`
FROM `mytable`
ORDER BY `mycol`
LIMIT 10, 20

2.) Thinking out of the box, most of the time users don't need to know the EXACT size of the table, an approximate is often good enough.

SELECT `TABLE_ROWS` AS `rows_approx`
FROM `INFORMATION_SCHEMA`.`TABLES`
WHERE `TABLE_SCHEMA` = DATABASE()
  AND `TABLE_TYPE` = "BASE TABLE"
  AND `TABLE_NAME` = ?

How to generate unique ID with node.js

nanoid achieves exactly the same thing that you want.

Example usage:

const { nanoid } = require("nanoid")

console.log(nanoid())
//=> "n340M4XJjATNzrEl5Qvsh"

Ruby on Rails 3 Can't connect to local MySQL server through socket '/tmp/mysql.sock' on OSX

The default location for the MySQL socket on Mac OS X is /var/mysql/mysql.sock.

Solving "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection" InvalidOperationException

Bottom Line

Your code has retrieved data (entities) via entity-framework with lazy-loading enabled and after the DbContext has been disposed, your code is referencing properties (related/relationship/navigation entities) that was not explicitly requested.

More Specifically

The InvalidOperationException with this message always means the same thing: you are requesting data (entities) from entity-framework after the DbContext has been disposed.

A simple case:

(these classes will be used for all examples in this answer, and assume all navigation properties have been configured correctly and have associated tables in the database)

public class Person
{
  public int Id { get; set; }
  public string name { get; set; }
  public int? PetId { get; set; }
  public Pet Pet { get; set; }
}

public class Pet 
{
  public string name { get; set; }
}

using (var db = new dbContext())
{
  var person = db.Persons.FirstOrDefaultAsync(p => p.id == 1);
}

Console.WriteLine(person.Pet.Name);

The last line will throw the InvalidOperationException because the dbContext has not disabled lazy-loading and the code is accessing the Pet navigation property after the Context has been disposed by the using statement.

Debugging

How do you find the source of this exception? Apart from looking at the exception itself, which will be thrown exactly at the location where it occurs, the general rules of debugging in Visual Studio apply: place strategic breakpoints and inspect your variables, either by hovering the mouse over their names, opening a (Quick)Watch window or using the various debugging panels like Locals and Autos.

If you want to find out where the reference is or isn't set, right-click its name and select "Find All References". You can then place a breakpoint at every location that requests data, and run your program with the debugger attached. Every time the debugger breaks on such a breakpoint, you need to determine whether your navigation property should have been populated or if the data requested is necessary.

Ways to Avoid

Disable Lazy-Loading

public class MyDbContext : DbContext
{
  public MyDbContext()
  {
    this.Configuration.LazyLoadingEnabled = false;
  }
}

Pros: Instead of throwing the InvalidOperationException the property will be null. Accessing properties of null or attempting to change the properties of this property will throw a NullReferenceException.

How to explicitly request the object when needed:

using (var db = new dbContext())
{
  var person = db.Persons
    .Include(p => p.Pet)
    .FirstOrDefaultAsync(p => p.id == 1);
}
Console.WriteLine(person.Pet.Name);  // No Exception Thrown

In the previous example, Entity Framework will materialize the Pet in addition to the Person. This can be advantageous because it’s a single call the the database. (However, there can also be huge performance problems depending on the number of returned results and the number of navigation properties requested, in this instance, there would be no performance penalty because both instances are only a single record and a single join).

or

using (var db = new dbContext())
{
  var person = db.Persons.FirstOrDefaultAsync(p => p.id == 1);

  var pet = db.Pets.FirstOrDefaultAsync(p => p.id == person.PetId);
}
Console.WriteLine(person.Pet.Name);  // No Exception Thrown

In the previous example, Entity Framework will materialize the Pet independently of the Person by making an additional call to the database. By default, Entity Framework tracks objects it has retrieved from the database and if it finds navigation properties that match it will auto-magically populate these entities. In this instance because the PetId on the Person object matches the Pet.Id, Entity Framework will assign the Person.Pet to the Pet value retrieved, before the value is assigned to the pet variable.

I always recommend this approach as it forces programmers to understand when and how code is request data via Entity Framework. When code throws a null reference exception on a property of an entity, you can almost always be sure you have not explicitly requested that data.

The executable was signed with invalid entitlements

I have found that "get-task-allow" needs to be checked for Development builds but unchecked for Distribution builds. The easiest way to accomplish this (AFAIK) is to have two entitlements files in your project: Entitlements.plist and EntitlementsDebug.plist - and to reference the proper one in the build project settings for the various configurations in your project.

release Selenium chromedriver.exe from memory

You should apply close before than quit

driver.close()
driver.quit()

Serializing enums with Jackson

An easy way to serialize Enum is using @JsonFormat annotation. @JsonFormat can configure the serialization of a Enum in three ways.

@JsonFormat.Shape.STRING
public Enum OrderType {...}

uses OrderType::name as the serialization method. Serialization of OrderType.TypeA is “TYPEA”

@JsonFormat.Shape.NUMBER
Public Enum OrderTYpe{...}

uses OrderType::ordinal as the serialization method. Serialization of OrderType.TypeA is 1

@JsonFormat.Shape.OBJECT
Public Enum OrderType{...}

treats OrderType as a POJO. Serialization of OrderType.TypeA is {"id":1,"name":"Type A"}

JsonFormat.Shape.OBJECT is what you need in your case.

A little more complicated way is your solution, specifying a serializer for the Enum.

Check out this reference: https://fasterxml.github.io/jackson-annotations/javadoc/2.2.0/com/fasterxml/jackson/annotation/JsonFormat.html

phpMyAdmin - The MySQL Extension is Missing

Your installation is missing some php modules, there should be a list of required modules in the phpmyadmin readme. If you recently enabled the modules, try restarting the apache service / daemon.

Edit: As it seems, there is no single "enable these modules" in the docs, so enable either mysql or mysqli in your php.ini (you might need to install it first).

The two messages are not important if you do not intend to upload or download compressed file within phpMyAdmin. If you do, enable the zlib and / or bz2 modules.

How to print Unicode character in Python?

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

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

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

>>>str = "??"


>>>print (str)
??

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

How to use Python's pip to download and keep the zipped files for a package?

pip wheel is another option you should consider:

pip wheel mypackage -w .\outputdir

It will download packages and their dependencies to a directory (current working directory by default), but it performs the additional step of converting any source packages to wheels.

It conveniently supports requirements files:

pip wheel -r requirements.txt -w .\outputdir

Add the --no-deps argument if you only want the specifically requested packages:

pip wheel mypackage -w .\outputdir --no-deps

Remove leading or trailing spaces in an entire column of data

Without using a formula you can do this with 'Text to columns'.

  • Select the column that has the trailing spaces in the cells.
  • Click 'Text to columns' from the 'Data' tab, then choose option 'Fixed width'.
  • Set a break line so the longest text will fit. If your largest cell has 100 characters you can set the breakline on 200 or whatever you want.
  • Finish the operation.
  • You can now delete the new column Excel has created.

The 'side-effect' is that Excel has removed all trailing spaces in the original column.

How to get current route in Symfony 2?

I think this is the easiest way to do this:

class MyController extends Controller
{
    public function myAction($_route)
    {
        var_dump($_route);
    }

    .....

Convert an object to an XML string

    public static string Serialize(object dataToSerialize)
    {
        if(dataToSerialize==null) return null;

        using (StringWriter stringwriter = new System.IO.StringWriter())
        {
            var serializer = new XmlSerializer(dataToSerialize.GetType());
            serializer.Serialize(stringwriter, dataToSerialize);
            return stringwriter.ToString();
        }
    }

    public static T Deserialize<T>(string xmlText)
    {
        if(String.IsNullOrWhiteSpace(xmlText)) return default(T);

        using (StringReader stringReader = new System.IO.StringReader(xmlText))
        {
            var serializer = new XmlSerializer(typeof(T));
            return (T)serializer.Deserialize(stringReader);
        }
    }

Android: How to open a specific folder via Intent and show its content in a file browser?

File temp = File.createTempFile("preview", ".png" );
String fullfileName= temp.getAbsolutePath();
final String fileName = Uri.parse(fullfileName)
                    .getLastPathSegment();
final String filePath = fullfileName.
                     substring(0,fullfileName.lastIndexOf(File.separator));
Log.d("filePath", "filePath: " + filePath);

fullfileName:

/mnt/sdcard/Download_Manager_Farsi/preview.png

filePath:

/mnt/sdcard/Download_Manager_Farsi

How to upper case every first letter of word in a string?

sString = sString.toLowerCase();
sString = Character.toString(sString.charAt(0)).toUpperCase()+sString.substring(1);

MySQL - UPDATE multiple rows with different values in one query

MySQL allows a more readable way to combine multiple updates into a single query. This seems to better fit the scenario you describe, is much easier to read, and avoids those difficult-to-untangle multiple conditions.

INSERT INTO table_users (cod_user, date, user_rol, cod_office)
VALUES
('622057', '12082014', 'student', '17389551'),
('2913659', '12082014', 'assistant','17389551'),
('6160230', '12082014', 'admin', '17389551')
ON DUPLICATE KEY UPDATE
 cod_user=VALUES(cod_user), date=VALUES(date)

This assumes that the user_rol, cod_office combination is a primary key. If only one of these is the primary key, then add the other field to the UPDATE list. If neither of them is a primary key (that seems unlikely) then this approach will always create new records - probably not what is wanted.

However, this approach makes prepared statements easier to build and more concise.

html cellpadding the left side of a cell

I use inline css all the time BECAUSE.... I want absolute control of the design and place different things aligned differently from cell to cell.

It is not hard to understand...

Anyway, I just put something like this inside my tag:

style='padding:5px 10px 5px 5px'

Where the order represents top, right, bottom and left.

Create table in SQLite only if it doesn't exist already

Am going to try and add value to this very good question and to build on @BrittonKerin's question in one of the comments under @David Wolever's fantastic answer. Wanted to share here because I had the same challenge as @BrittonKerin and I got something working (i.e. just want to run a piece of code only IF the table doesn't exist).

        # for completeness lets do the routine thing of connections and cursors
        conn = sqlite3.connect(db_file, timeout=1000) 

        cursor = conn.cursor() 

        # get the count of tables with the name  
        tablename = 'KABOOM' 
        cursor.execute("SELECT count(name) FROM sqlite_master WHERE type='table' AND name=? ", (tablename, ))

        print(cursor.fetchone()) # this SHOULD BE in a tuple containing count(name) integer.

        # check if the db has existing table named KABOOM
        # if the count is 1, then table exists 
        if cursor.fetchone()[0] ==1 : 
            print('Table exists. I can do my custom stuff here now.... ')
            pass
        else: 
           # then table doesn't exist. 
           custRET = myCustFunc(foo,bar) # replace this with your custom logic

Java Programming: call an exe from Java and passing parameters

You're on the right track. The two constructors accept arguments, or you can specify them post-construction with ProcessBuilder#command(java.util.List) and ProcessBuilder#command(String...).

Why am I getting string does not name a type Error?

string does not name a type. The class in the string header is called std::string.

Please do not put using namespace std in a header file, it pollutes the global namespace for all users of that header. See also "Why is 'using namespace std;' considered a bad practice in C++?"

Your class should look like this:

#include <string>

class Game
{
    private:
        std::string white;
        std::string black;
        std::string title;
    public:
        Game(std::istream&, std::ostream&);
        void display(colour, short);
};

parse html string with jquery

just add container element befor your img element just to be sure that your intersted element not the first one, tested in ie,ff

file_get_contents() Breaks Up UTF-8 Characters

I had similar problem with polish language

I tried:

$fileEndEnd = mb_convert_encoding($fileEndEnd, 'UTF-8', mb_detect_encoding($fileEndEnd, 'UTF-8', true));

I tried:

$fileEndEnd = utf8_encode ( $fileEndEnd );

I tried:

$fileEndEnd = iconv( "UTF-8", "UTF-8", $fileEndEnd );

And then -

$fileEndEnd = mb_convert_encoding($fileEndEnd, 'HTML-ENTITIES', "UTF-8");

This last worked perfectly !!!!!!

DropdownList DataSource

You can bind the DropDownList in different ways by using List, Dictionary, Enum, DataSet DataTable.
Main you have to consider three thing while binding the datasource of a dropdown.

  1. DataSource - Name of the dataset or datatable or your datasource
  2. DataValueField - These field will be hidden
  3. DataTextField - These field will be displayed on the dropdwon.

you can use following code to bind a dropdownlist to a datasource as a datatable:

  SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnString"].ConnectionString);

    SqlCommand cmd = new SqlCommand("Select * from tblQuiz", con);

    SqlDataAdapter da = new SqlDataAdapter(cmd);

    DataTable dt=new DataTable();
    da.Fill(dt);

    DropDownList1.DataTextField = "QUIZ_Name";
    DropDownList1.DataValueField = "QUIZ_ID"

    DropDownList1.DataSource = dt;
    DropDownList1.DataBind();

if you want to process on selection of dropdownlist, then you have to change AutoPostBack="true" you can use SelectedIndexChanged event to write your code.

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    string strQUIZ_ID=DropDownList1.SelectedValue;
    string strQUIZ_Name=DropDownList1.SelectedItem.Text;
    // Your code..............
}

Angular - Use pipes in services and components

As usual in Angular, you can rely on dependency injection:

import { DatePipe } from '@angular/common';

class MyService {

  constructor(private datePipe: DatePipe) {}

  transformDate(date) {
    return this.datePipe.transform(date, 'yyyy-MM-dd');
  }
}

Add DatePipe to your providers list in your module; if you forget to do this you'll get an error no provider for DatePipe:

providers: [DatePipe,...]

Update Angular 6: Angular 6 now offers pretty much every formatting functions used by the pipes publicly. For example, you can now use the formatDate function directly.

import { formatDate } from '@angular/common';

class MyService {

  constructor(@Inject(LOCALE_ID) private locale: string) {}

  transformDate(date) {
    return formatDate(date, 'yyyy-MM-dd', this.locale);
  }
}

Before Angular 5: Be warned though that the DatePipe was relying on the Intl API until version 5, which is not supported by all browsers (check the compatibility table).

If you're using older Angular versions, you should add the Intl polyfill to your project to avoid any problem. See this related question for a more detailed answer.

Access to Image from origin 'null' has been blocked by CORS policy

Under the covers there will be some form of URL loading request. You can't load images or any other content via this method from a local file system.

Your image needs to be loaded via a web server, so accessed via a proper http URL.

failed to load ad : 3

This error can be because of too much reasons. Try first with testAds ca-app-pub id to avoid admob account issues.

Check that you extends AppCompatActivity in your mainActivity, in my case that was the issue

Also check all this steps again https://developers.google.com/admob/android/quick-start?hl=en-419#import_the_mobile_ads_sdk

Compiler error: "initializer element is not a compile-time constant"

When you define a variable outside the scope of a function, that variable's value is actually written into your executable file. This means you can only use a constant value. Since you don't know everything about the runtime environment at compile time (which classes are available, what is their structure, etc.), you cannot create objective c objects until runtime, with the exception of constant strings, which are given a specific structure and guaranteed to stay that way. What you should do is initialize the variable to nil and use +initialize to create your image. initialize is a class method which will be called before any other method is called on your class.

Example:

NSImage *imageSegment = nil;
+ (void)initialize {
    if(!imageSegment)
        imageSegment = [[NSImage alloc] initWithContentsOfFile:@"/User/asd.jpg"];
}
- (id)init {
    self = [super init];
    if (self) {
        // Initialization code here.
    }

    return self;
}

What is the difference between Google App Engine and Google Compute Engine?

App Engine is a Platform-as-a-Service. It means that you simply deploy your code, and the platform does everything else for you. For example, if your app becomes very successful, App Engine will automatically create more instances to handle the increased volume.

Read more about App Engine

Compute Engine is an Infrastructure-as-a-Service. You have to create and configure your own virtual machine instances. It gives you more flexibility and generally costs much less than App Engine. The drawback is that you have to manage your app and virtual machines yourself.

Read more about Compute Engine

You can mix both App Engine and Compute Engine, if necessary. They both work well with the other parts of the Google Cloud Platform.

EDIT (May 2016):

One more important distinction: projects running on App Engine can scale down to zero instances if no requests are coming in. This is extremely useful at the development stage as you can go for weeks without going over the generous free quota of instance-hours. Flexible runtime (i.e. "managed VMs") require at least one instance to run constantly.

EDIT (April 2017):

Cloud Functions (currently in beta) is the next level up from App Engine in terms of abstraction - no instances! It allows developers to deploy bite-size pieces of code that execute in response to different events, which may include HTTP requests, changes in Cloud Storage, etc.

The biggest difference with App Engine is that functions are priced per 100 milliseconds, while App Engine's instances shut down only after 15 minutes of inactivity. Another advantage is that Cloud Functions execute immediately, while a call to App Engine may require a new instance - and cold-starting a new instance may take a few seconds or longer (depending on runtime and your code).

This makes Cloud Functions ideal for (a) rare calls - no need to keep an instance live just in case something happens, (b) rapidly changing loads where instances are often spinning and shutting down, and possibly more use cases.

Read more about Cloud Functions

Server Error in '/' Application. ASP.NET

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

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

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

How to write JUnit test with Spring Autowire?

I've done it with two annotations for test class: @RunWith(SpringRunner.class) and @SpringBootTest. Example:

@RunWith(SpringRunner.class )
@SpringBootTest
public class ProtocolTransactionServiceTest {

    @Autowired
    private ProtocolTransactionService protocolTransactionService;
}

@SpringBootTest loads the whole context, which was OK in my case.

Check if my SSL Certificate is SHA1 or SHA2

I had to modify this slightly to be used on a Windows System. Here's the one-liner version for a windows box.

openssl.exe s_client -connect yoursitename.com:443 > CertInfo.txt && openssl x509 -text -in CertInfo.txt | find "Signature Algorithm" && del CertInfo.txt /F

Tested on Server 2012 R2 using http://iweb.dl.sourceforge.net/project/gnuwin32/openssl/0.9.8h-1/openssl-0.9.8h-1-bin.zip

Entity Framework Core: A second operation started on this context before a previous operation completed

In my case I use a template component in Blazor.

 <BTable ID="Table1" TotalRows="MyList.Count()">

The problem is calling a method (Count) in the component header. To resolve the problem I changed it like this :

int total = MyList.Count();

and later :

<BTable ID="Table1" TotalRows="total">

How to determine if OpenSSL and mod_ssl are installed on Apache2

The default Apache install is configured to send this information on the Server header line. You can view this for any server using the curl command.

$ curl --head http://localhost/
HTTP/1.1 200 OK
Date: Fri, 04 Sep 2009 08:14:03 GMT
Server: Apache/2.2.8 (Unix) mod_ssl/2.2.8 OpenSSL/0.9.8a DAV/2 PHP/5.2.6 SVN/1.5.4 proxy_html/3.0.0

How to get the first five character of a String

Just a heads up there is a new way to do this in C# 8.0: Range operators

Microsoft Docs

Or as I like to call em, Pandas slices.

Old way:

string newString = oldstring.Substring(0, 5);

New way:

string newString = oldstring[..5];

Which at first glance appears like a pretty bad tradeoff of some readability for shorter code but the new feature gives you

  1. a standard syntax for slicing arrays (and therefore strings)
  2. cool stuff like this:

    var slice1 = list[2..^3]; // list[Range.Create(2, Index.CreateFromEnd(3))]

    var slice2 = list[..^3]; // list[Range.ToEnd(Index.CreateFromEnd(3))]

    var slice3 = list[2..]; // list[Range.FromStart(2)]

    var slice4 = list[..]; // list[Range.All]

Add spaces between the characters of a string in Java?

StringBuilder result = new StringBuilder();
for (int i = 0; i < input.length(); i++) {
   if (i > 0) {
      result.append(" ");
    }

   result.append(input.charAt(i));
}

System.out.println(result.toString());

Find non-ASCII characters in varchar columns using SQL Server

Here is a UDF I built to detectc columns with extended ascii charaters. It is quick and you can extended the character set you want to check. The second parameter allows you to switch between checking anything outside the standard character set or allowing an extended set:

create function [dbo].[udf_ContainsNonASCIIChars]
(
@string nvarchar(4000),
@checkExtendedCharset bit
)
returns bit
as
begin

    declare @pos int = 0;
    declare @char varchar(1);
    declare @return bit = 0;

    while @pos < len(@string)
    begin
        select @char = substring(@string, @pos, 1)
        if ascii(@char) < 32 or ascii(@char) > 126 
            begin
                if @checkExtendedCharset = 1
                    begin
                        if ascii(@char) not in (9,124,130,138,142,146,150,154,158,160,170,176,180,181,183,184,185,186,192,193,194,195,196,197,199,200,201,202,203,204,205,206,207,209,210,211,212,213,214,216,217,218,219,220,221,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,248,249,250,251,252,253,254,255)
                            begin
                                select @return = 1;
                                select @pos = (len(@string) + 1)
                            end
                        else
                            begin
                                select @pos = @pos + 1
                            end
                    end
                else
                    begin
                        select @return = 1;
                        select @pos = (len(@string) + 1)    
                    end
            end
        else
            begin
                select @pos = @pos + 1
            end
    end

    return @return;

end

USAGE:

select Address1 
from PropertyFile_English
where udf_ContainsNonASCIIChars(Address1, 1) = 1

UnsatisfiedDependencyException: Error creating bean with name

Check out the table structure of Client table, if there is a mismatch between table structure in db and the entity, you would get this error..

I had this error which was coming due to datatype mismatch of primary key between db table and the entity ...

Javascript wait() function

You shouldn't edit it, you should completely scrap it.

Any attempt to make execution stop for a certain amount of time will lock up the browser and switch it to a Not Responding state. The only thing you can do is use setTimeout correctly.

How to run Linux commands in Java?

Runtime run = Runtime.getRuntime();  
//The best possible I found is to construct a command which you want to execute  
//as a string and use that in exec. If the batch file takes command line arguments  
//the command can be constructed a array of strings and pass the array as input to  
//the exec method. The command can also be passed externally as input to the method.  

Process p = null;  
String cmd = "ls";  
try {  
    p = run.exec(cmd);  

    p.getErrorStream();  
    p.waitFor();

}  
catch (IOException e) {  
    e.printStackTrace();  
    System.out.println("ERROR.RUNNING.CMD");  

}finally{
    p.destroy();
}  

Why does my Spring Boot App always shutdown immediately after starting?

My application is Spring boot batch and commenting below line in application.properties resolved the problem

spring.main.web-application-type=none

Python Library Path

import sys
sys.path

How to get Django and ReactJS to work together?

A note for anyone who is coming from a backend or Django based role and trying to work with ReactJS: No one manages to setup ReactJS enviroment successfully in the first try :)

There is a blog from Owais Lone which is available from http://owaislone.org/blog/webpack-plus-reactjs-and-django/ ; however syntax on Webpack configuration is way out of date.

I suggest you follow the steps mentioned in the blog and replace the webpack configuration file with the content below. However if you're new to both Django and React, chew one at a time because of the learning curve you will probably get frustrated.

var path = require('path');
var webpack = require('webpack');
var BundleTracker = require('webpack-bundle-tracker');

module.exports = {
    context: __dirname,
    entry: './static/assets/js/index',
    output: {
        path: path.resolve('./static/assets/bundles/'),
        filename: '[name]-[hash].js'
    },
    plugins: [
        new BundleTracker({filename: './webpack-stats.json'})
    ],

 module: {
    loaders: [
      {
        test: /\.jsx?$/,
        loader: 'babel-loader',
        exclude: /node_modules/,
        query: {
          presets: ['es2015', 'react']
        }
      }
    ]
  },


  resolve: {
        modules: ['node_modules', 'bower_components'],
        extensions: ['.js', '.jsx']
    }
};

Read and write a String from text file

I had to recode like this:

let path = NSBundle.mainBundle().pathForResource("Output_5", ofType: "xml")
let text = try? NSString(contentsOfFile: path! as String, encoding: NSUTF8StringEncoding)
print(text)

Android. WebView and loadData

As I understand it, loadData() simply generates a data: URL with the data provide it.

Read the javadocs for loadData():

If the value of the encoding parameter is 'base64', then the data must be encoded as base64. Otherwise, the data must use ASCII encoding for octets inside the range of safe URL characters and use the standard %xx hex encoding of URLs for octets outside that range. For example, '#', '%', '\', '?' should be replaced by %23, %25, %27, %3f respectively.

The 'data' scheme URL formed by this method uses the default US-ASCII charset. If you need need to set a different charset, you should form a 'data' scheme URL which explicitly specifies a charset parameter in the mediatype portion of the URL and call loadUrl(String) instead. Note that the charset obtained from the mediatype portion of a data URL always overrides that specified in the HTML or XML document itself.

Therefore, you should either use US-ASCII and escape any special characters yourself, or just encode everything using Base64. The following should work, assuming you use UTF-8 (I haven't tested this with latin1):

String data = ...;  // the html data
String base64 = android.util.Base64.encodeToString(data.getBytes("UTF-8"), android.util.Base64.DEFAULT);
webView.loadData(base64, "text/html; charset=utf-8", "base64");

How do I create an average from a Ruby array?

what I don't like about the accepted solution

arr = [5, 6, 7, 8]
arr.inject{ |sum, el| sum + el }.to_f / arr.size
=> 6.5

is that it does not really work in a purely functional way. we need a variable arr to compute arr.size at the end.

to solve this purely functionally we need to keep track of two values: the sum of all elements, and the number of elements.

[5, 6, 7, 8].inject([0.0,0]) do |r,ele|
    [ r[0]+ele, r[1]+1 ]
end.inject(:/)
=> 6.5   

Santhosh improved on this solution: instead of the argument r being an array, we could use destructuring to immediatly pick it apart into two variables

[5, 6, 7, 8].inject([0.0,0]) do |(sum, size), ele| 
   [ sum + ele, size + 1 ]
end.inject(:/)

if you want to see how it works, add some puts:

[5, 6, 7, 8].inject([0.0,0]) do |(sum, size), ele| 
   r2 = [ sum + ele, size + 1 ]
   puts "adding #{ele} gives #{r2}"
   r2
end.inject(:/)

adding 5 gives [5.0, 1]
adding 6 gives [11.0, 2]
adding 7 gives [18.0, 3]
adding 8 gives [26.0, 4]
=> 6.5

We could also use a struct instead of an array to contain the sum and the count, but then we have to declare the struct first:

R=Struct.new(:sum, :count)
[5, 6, 7, 8].inject( R.new(0.0, 0) ) do |r,ele|
    r.sum += ele
    r.count += 1
    r
end.inject(:/)

How to convert an xml string to a dictionary?

I have a recursive method to get a dictionary from a lxml element

    def recursive_dict(element):
        return (element.tag.split('}')[1],
                dict(map(recursive_dict, element.getchildren()),
                     **element.attrib))

How to navigate through a vector using iterators? (C++)

Here is an example of accessing the ith index of a std::vector using an std::iterator within a loop which does not require incrementing two iterators.

std::vector<std::string> strs = {"sigma" "alpha", "beta", "rho", "nova"};
int nth = 2;
std::vector<std::string>::iterator it;
for(it = strs.begin(); it != strs.end(); it++) {
    int ith = it - strs.begin();
    if(ith == nth) {
        printf("Iterator within  a for-loop: strs[%d] = %s\n", ith, (*it).c_str());
    }
}

Without a for-loop

it = strs.begin() + nth;
printf("Iterator without a for-loop: strs[%d] = %s\n", nth, (*it).c_str());

and using at method:

printf("Using at position: strs[%d] = %s\n", nth, strs.at(nth).c_str());