Programs & Examples On #String

A string is a finite sequence of symbols, commonly used for text, though sometimes for arbitrary data.

C# declare empty string array

Try this

string[] arr = new string[] {};

Perl - If string contains text?

If you just need to search for one string within another, use the index function (or rindex if you want to start scanning from the end of the string):

if (index($string, $substring) != -1) {
   print "'$string' contains '$substring'\n";
}

To search a string for a pattern match, use the match operator m//:

if ($string =~ m/pattern/) {
    print "'$string' matches the pattern\n";       
}

javascript date to string

A little bit simpler using regex and toJSON().

var now = new Date();
var timeRegex = /^.*T(\d{2}):(\d{2}):(\d{2}).*$/
var dateRegex = /^(\d{4})-(\d{2})-(\d{2})T.*$/
var dateData = dateRegex.exec(now.toJSON());
var timeData = timeRegex.exec(now.toJSON());
var myFormat = dateData[1]+dateData[2]+dateData[3]+timeData[1]+timeData[2]+timeData[3]

Which at the time of writing gives you "20151111180924".

The good thing of using toJSON() is that everything comes already padded.

C#: Limit the length of a string?

If this is in a class property you could do it in the setter:

public class FooClass
{
   private string foo;
   public string Foo
   {
     get { return foo; }
     set
     {
       if(!string.IsNullOrEmpty(value) && value.Length>5)
       {
            foo=value.Substring(0,5);
       }
       else
            foo=value;
     }
   }
}

Remove all HTMLtags in a string (with the jquery text() function)

var myContent = '<div id="test">Hello <span>world!</span></div>';

alert($(myContent).text());

That results in hello world. Does that answer your question?

http://jsfiddle.net/D2tEf/ for an example

Remove portion of a string after a certain character

$variable = substr($variable, 0, strpos($variable, "By"));

In plain english: Give me the part of the string starting at the beginning and ending at the position where you first encounter the deliminator.

Python: How exactly can you take a string, split it, reverse it and join it back together again?

Do you mean like this?

import string
astr='a(b[c])d'

deleter=string.maketrans('()[]','    ')
print(astr.translate(deleter))
# a b c  d
print(astr.translate(deleter).split())
# ['a', 'b', 'c', 'd']
print(list(reversed(astr.translate(deleter).split())))
# ['d', 'c', 'b', 'a']
print(' '.join(reversed(astr.translate(deleter).split())))
# d c b a

Splitting a Java String by the pipe symbol using split("|")

Use proper escaping: string.split("\\|")

Or, in Java 5+, use the helper Pattern.quote() which has been created for exactly this purpose:

string.split(Pattern.quote("|"))

which works with arbitrary input strings. Very useful when you need to quote / escape user input.

Checking character length in ruby

Ruby provides a built-in function for checking the length of a string. Say it's called s:

if s.length <= 25
  # We're OK
else
  # Too long
end

Convert a list of characters into a string

This works in many popular languages like JavaScript and Ruby, why not in Python?

>>> ['a', 'b', 'c'].join('')
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
AttributeError: 'list' object has no attribute 'join'

Strange enough, in Python the join method is on the str class:

# this is the Python way
"".join(['a','b','c','d'])

Why join is not a method in the list object like in JavaScript or other popular script languages? It is one example of how the Python community thinks. Since join is returning a string, it should be placed in the string class, not on the list class, so the str.join(list) method means: join the list into a new string using str as a separator (in this case str is an empty string).

Somehow I got to love this way of thinking after a while. I can complain about a lot of things in Python design, but not about its coherence.

How to split a single column values to multiple column values?

;WITH Split_Names (Name, xmlname)
AS
(
    SELECT 
    Name,
    CONVERT(XML,'<Names><name>'  
    + REPLACE(Name,' ', '</name><name>') + '</name></Names>') AS xmlname
      FROM somenames
)

 SELECT       
 xmlname.value('/Names[1]/name[1]','varchar(100)') AS first_name,    
 xmlname.value('/Names[1]/name[2]','varchar(100)') AS last_name
 FROM Split_Names

and also check the link below for reference

http://jahaines.blogspot.in/2009/06/converting-delimited-string-of-values.html

How many bytes in a JavaScript string?

A single element in a JavaScript String is considered to be a single UTF-16 code unit. That is to say, Strings characters are stored in 16-bit (1 code unit), and 16-bit is equal to 2 bytes (8-bit = 1 byte).

The charCodeAt() method can be used to return an integer between 0 and 65535 representing the UTF-16 code unit at the given index.

The codePointAt() can be used to return the entire code point value for Unicode characters, e.g. UTF-32.

When a UTF-16 character can't be represented in a single 16-bit code unit, it will have a surrogate pair and therefore use two code units( 2 x 16-bit = 4 bytes)

See Unicode encodings for different encodings and their code ranges.

Difference between text and varchar (character varying)

As "Character Types" in the documentation points out, varchar(n), char(n), and text are all stored the same way. The only difference is extra cycles are needed to check the length, if one is given, and the extra space and time required if padding is needed for char(n).

However, when you only need to store a single character, there is a slight performance advantage to using the special type "char" (keep the double-quotes — they're part of the type name). You get faster access to the field, and there is no overhead to store the length.

I just made a table of 1,000,000 random "char" chosen from the lower-case alphabet. A query to get a frequency distribution (select count(*), field ... group by field) takes about 650 milliseconds, vs about 760 on the same data using a text field.

How to convert CharSequence to String?

By invoking its toString() method.

Returns a string containing the characters in this sequence in the same order as this sequence. The length of the string will be the length of this sequence.

How to check if a character is upper-case in Python?

words = x.split("_")
for word in words:
    if word[0] == word[0].upper() and word[1:] == word[1:].lower():
        print word, "is conformant"
    else:
        print word, "is non conformant"

Is it better practice to use String.format over string Concatenation in Java?

One problem with .format is that you lose static type safety. You can have too few arguments for your format, and you can have the wrong types for the format specifiers - both leading to an IllegalFormatException at runtime, so you might end up with logging code that breaks production.

In contrast, the arguments to + can be tested by the compiler.

The security history of (on which the format function is modeled) is long and frightening.

Insert value into a string at a certain position?

If you just want to insert a value at a certain position in a string, you can use the String.Insert method:

public string Insert(int startIndex, string value)

Example:

"abc".Insert(2, "XYZ") == "abXYZc"

PHP substring extraction. Get the string before the first '/' or the whole string

The function strstr() in PHP 5.3 should do this job.. The third parameter however should be set to true..

But if you're not using 5.3, then the function below should work accurately:

function strbstr( $str, $char, $start=0 ){
    if ( isset($str[ $start ]) && $str[$start]!=$char ){
        return $str[$start].strbstr( $str, $char, $start+1 );
    }
}

I haven't tested it though, but this should work just fine.. And it's pretty fast as well

Converting a float to a string without rounding it

I know this is too late but for those who are coming here for the first time, I'd like to post a solution. I have a float value index and a string imgfile and I had the same problem as you. This is how I fixed the issue

index = 1.0
imgfile = 'data/2.jpg'
out = '%.1f,%s' % (index,imgfile)
print out

The output is

1.0,data/2.jpg

You may modify this formatting example as per your convenience.

How can I extract a number from a string in JavaScript?

For this specific example,

 var thenum = thestring.replace( /^\D+/g, ''); // replace all leading non-digits with nothing

in the general case:

 thenum = "foo3bar5".match(/\d+/)[0] // "3"

Since this answer gained popularity for some reason, here's a bonus: regex generator.

_x000D_
_x000D_
function getre(str, num) {_x000D_
  if(str === num) return 'nice try';_x000D_
  var res = [/^\D+/g,/\D+$/g,/^\D+|\D+$/g,/\D+/g,/\D.*/g, /.*\D/g,/^\D+|\D.*$/g,/.*\D(?=\d)|\D+$/g];_x000D_
  for(var i = 0; i < res.length; i++)_x000D_
    if(str.replace(res[i], '') === num) _x000D_
      return 'num = str.replace(/' + res[i].source + '/g, "")';_x000D_
  return 'no idea';_x000D_
};_x000D_
function update() {_x000D_
  $ = function(x) { return document.getElementById(x) };_x000D_
  var re = getre($('str').value, $('num').value);_x000D_
  $('re').innerHTML = 'Numex speaks: <code>' + re + '</code>';_x000D_
}
_x000D_
<p>Hi, I'm Numex, the Number Extractor Oracle._x000D_
<p>What is your string? <input id="str" value="42abc"></p>_x000D_
<p>What number do you want to extract? <input id="num" value="42"></p>_x000D_
<p><button onclick="update()">Insert Coin</button></p>_x000D_
<p id="re"></p>
_x000D_
_x000D_
_x000D_

How to check whether a string contains a substring in Ruby

user_input = gets.chomp
user_input.downcase!

if user_input.include?('substring')
  # Do something
end

This will help you check if the string contains substring or not

puts "Enter a string"
user_input = gets.chomp  # Ex: Tommy
user_input.downcase!    #  tommy


if user_input.include?('s')
    puts "Found"
else
    puts "Not found"
end

Standard way to embed version into python package?

There doesn't seem to be a standard way to embed a version string in a python package. Most packages I've seen use some variant of your solution, i.e. eitner

  1. Embed the version in setup.py and have setup.py generate a module (e.g. version.py) containing only version info, that's imported by your package, or

  2. The reverse: put the version info in your package itself, and import that to set the version in setup.py

Regex for remove everything after | (with | )

If you want to get everything after | excluding set character use this code.

[^|]*$

Others solutions \|.*$

Results : | mypcworld

This one [^|]*$

Results : mypcworld

http://regexr.com/3elkd

Convert string to datetime in vb.net

Pass the decode pattern to ParseExact

Dim d as string = "201210120956"
Dim dt = DateTime.ParseExact(d, "yyyyMMddhhmm", Nothing)

ParseExact is available only from Net FrameWork 2.0.
If you are still on 1.1 you could use Parse, but you need to provide the IFormatProvider adequate to your string

String's Maximum length in Java - calling length() method

java.io.DataInput.readUTF() and java.io.DataOutput.writeUTF(String) say that a String object is represented by two bytes of length information and the modified UTF-8 representation of every character in the string. This concludes that the length of String is limited by the number of bytes of the modified UTF-8 representation of the string when used with DataInput and DataOutput.

In addition, The specification of CONSTANT_Utf8_info found in the Java virtual machine specification defines the structure as follows.

CONSTANT_Utf8_info {
    u1 tag;
    u2 length;
    u1 bytes[length];
}

You can find that the size of 'length' is two bytes.

That the return type of a certain method (e.g. String.length()) is int does not always mean that its allowed maximum value is Integer.MAX_VALUE. Instead, in most cases, int is chosen just for performance reasons. The Java language specification says that integers whose size is smaller than that of int are converted to int before calculation (if my memory serves me correctly) and it is one reason to choose int when there is no special reason.

The maximum length at compilation time is at most 65536. Note again that the length is the number of bytes of the modified UTF-8 representation, not the number of characters in a String object.

String objects may be able to have much more characters at runtime. However, if you want to use String objects with DataInput and DataOutput interfaces, it is better to avoid using too long String objects. I found this limitation when I implemented Objective-C equivalents of DataInput.readUTF() and DataOutput.writeUTF(String).

Comparing strings in C# with OR in an if statement

Try:

    if (textBox1.Text == "" || textBox2.Text == "")
    {
        // do something..
    }

Instead of:

    if (textBox1.Text == string.Empty || textBox2.Text == string.Empty)
    {
        // do something..
    }

Because string.Empty is different than - "".

How do I check if a string contains a specific word?

Peer to SamGoody and Lego Stormtroopr comments.

If you are looking for a PHP algorithm to rank search results based on proximity/relevance of multiple words here comes a quick and easy way of generating search results with PHP only:

Issues with the other boolean search methods such as strpos(), preg_match(), strstr() or stristr()

  1. can't search for multiple words
  2. results are unranked

PHP method based on Vector Space Model and tf-idf (term frequency–inverse document frequency):

It sounds difficult but is surprisingly easy.

If we want to search for multiple words in a string the core problem is how we assign a weight to each one of them?

If we could weight the terms in a string based on how representative they are of the string as a whole, we could order our results by the ones that best match the query.

This is the idea of the vector space model, not far from how SQL full-text search works:

function get_corpus_index($corpus = array(), $separator=' ') {

    $dictionary = array();

    $doc_count = array();

    foreach($corpus as $doc_id => $doc) {

        $terms = explode($separator, $doc);

        $doc_count[$doc_id] = count($terms);

        // tf–idf, short for term frequency–inverse document frequency, 
        // according to wikipedia is a numerical statistic that is intended to reflect 
        // how important a word is to a document in a corpus

        foreach($terms as $term) {

            if(!isset($dictionary[$term])) {

                $dictionary[$term] = array('document_frequency' => 0, 'postings' => array());
            }
            if(!isset($dictionary[$term]['postings'][$doc_id])) {

                $dictionary[$term]['document_frequency']++;

                $dictionary[$term]['postings'][$doc_id] = array('term_frequency' => 0);
            }

            $dictionary[$term]['postings'][$doc_id]['term_frequency']++;
        }

        //from http://phpir.com/simple-search-the-vector-space-model/

    }

    return array('doc_count' => $doc_count, 'dictionary' => $dictionary);
}

function get_similar_documents($query='', $corpus=array(), $separator=' '){

    $similar_documents=array();

    if($query!=''&&!empty($corpus)){

        $words=explode($separator,$query);

        $corpus=get_corpus_index($corpus, $separator);

        $doc_count=count($corpus['doc_count']);

        foreach($words as $word) {

            if(isset($corpus['dictionary'][$word])){

                $entry = $corpus['dictionary'][$word];


                foreach($entry['postings'] as $doc_id => $posting) {

                    //get term frequency–inverse document frequency
                    $score=$posting['term_frequency'] * log($doc_count + 1 / $entry['document_frequency'] + 1, 2);

                    if(isset($similar_documents[$doc_id])){

                        $similar_documents[$doc_id]+=$score;

                    }
                    else{

                        $similar_documents[$doc_id]=$score;

                    }
                }
            }
        }

        // length normalise
        foreach($similar_documents as $doc_id => $score) {

            $similar_documents[$doc_id] = $score/$corpus['doc_count'][$doc_id];

        }

        // sort from  high to low

        arsort($similar_documents);

    }   

    return $similar_documents;
}

CASE 1

$query = 'are';

$corpus = array(
    1 => 'How are you?',
);

$match_results=get_similar_documents($query,$corpus);
echo '<pre>';
    print_r($match_results);
echo '</pre>';

RESULT

Array
(
    [1] => 0.52832083357372
)

CASE 2

$query = 'are';

$corpus = array(
    1 => 'how are you today?',
    2 => 'how do you do',
    3 => 'here you are! how are you? Are we done yet?'
);

$match_results=get_similar_documents($query,$corpus);
echo '<pre>';
    print_r($match_results);
echo '</pre>';

RESULTS

Array
(
    [1] => 0.54248125036058
    [3] => 0.21699250014423
)

CASE 3

$query = 'we are done';

$corpus = array(
    1 => 'how are you today?',
    2 => 'how do you do',
    3 => 'here you are! how are you? Are we done yet?'
);

$match_results=get_similar_documents($query,$corpus);
echo '<pre>';
    print_r($match_results);
echo '</pre>';

RESULTS

Array
(
    [3] => 0.6813781191217
    [1] => 0.54248125036058
)

There are plenty of improvements to be made but the model provides a way of getting good results from natural queries, which don't have boolean operators such as strpos(), preg_match(), strstr() or stristr().

NOTA BENE

Optionally eliminating redundancy prior to search the words

  • thereby reducing index size and resulting in less storage requirement

  • less disk I/O

  • faster indexing and a consequently faster search.

1. Normalisation

  • Convert all text to lower case

2. Stopword elimination

  • Eliminate words from the text which carry no real meaning (like 'and', 'or', 'the', 'for', etc.)

3. Dictionary substitution

  • Replace words with others which have an identical or similar meaning. (ex:replace instances of 'hungrily' and 'hungry' with 'hunger')

  • Further algorithmic measures (snowball) may be performed to further reduce words to their essential meaning.

  • The replacement of colour names with their hexadecimal equivalents

  • The reduction of numeric values by reducing precision are other ways of normalising the text.

RESOURCES

Compare one String with multiple values in one expression

Small enhancement to perfectly valid @hmjd's answer: you can use following syntax:

class A {

  final Set<String> strings = new HashSet<>() {{
    add("val1");
    add("val2");
  }};

  // ...

  if (strings.contains(str.toLowerCase())) {
  }

  // ...
}

It allows you to initialize you Set in-place.

Split large string in n-size chunks in JavaScript

const getChunksFromString = (str, chunkSize) => {
    var regexChunk = new RegExp(`.{1,${chunkSize}}`, 'g')   // '.' represents any character
    return str.match(regexChunk)
}

Call it as needed

console.log(getChunksFromString("Hello world", 3))   // ["Hel", "lo ", "wor", "ld"]

Remove excess whitespace from within a string

You can use:

$str = trim(str_replace("  ", " ", $str));

This removes extra whitespaces from both sides of string and converts two spaces to one within the string. Note that this won't convert three or more spaces in a row to one! Another way I can suggest is using implode and explode that is safer but totally not optimum!

$str = implode(" ", array_filter(explode(" ", $str)));

My suggestion is using a native for loop or using regex to do this kind of job.

Converting integer to string in Python

>>> str(10)
'10'
>>> int('10')
10

Links to the documentation:

Conversion to a string is done with the builtin str() function, which basically calls the __str__() method of its parameter.

How to get a function name as a string?

I've seen a few answers that utilized decorators, though I felt a few were a bit verbose. Here's something I use for logging function names as well as their respective input and output values. I've adapted it here to just print the info rather than creating a log file and adapted it to apply to the OP specific example.

def debug(func=None):
    def wrapper(*args, **kwargs):
        try:
            function_name = func.__func__.__qualname__
        except:
            function_name = func.__qualname__
        return func(*args, **kwargs, function_name=function_name)
    return wrapper

@debug
def my_function(**kwargs):
    print(kwargs)

my_function()

Output:

{'function_name': 'my_function'}

Convert string to datetime

well, thought I should mention a solution I came across through some trying. Discovered whilst fixing a defect of someone comparing dates as strings.

new Date(Date.parse('01-01-1970 01:03:44'))

Converting string to numeric

As csgillespie said. stringsAsFactors is default on TRUE, which converts any text to a factor. So even after deleting the text, you still have a factor in your dataframe.

Now regarding the conversion, there's a more optimal way to do so. So I put it here as a reference :

> x <- factor(sample(4:8,10,replace=T))
> x
 [1] 6 4 8 6 7 6 8 5 8 4
Levels: 4 5 6 7 8
> as.numeric(levels(x))[x]
 [1] 6 4 8 6 7 6 8 5 8 4

To show it works.

The timings :

> x <- factor(sample(4:8,500000,replace=T))
> system.time(as.numeric(as.character(x)))
   user  system elapsed 
   0.11    0.00    0.11 
> system.time(as.numeric(levels(x))[x])
   user  system elapsed 
      0       0       0 

It's a big improvement, but not always a bottleneck. It gets important however if you have a big dataframe and a lot of columns to convert.

How to use PHP string in mySQL LIKE query?

DO it like

$query = mysql_query("SELECT * FROM table WHERE the_number LIKE '$yourPHPVAR%'");

Do not forget the % at the end

PHP - concatenate or directly insert variables in string

Between those two syntaxes, you should really choose the one you prefer :-)

Personally, I would go with your second solution in such a case (Variable interpolation), which I find easier to both write and read.

The result will be the same; and even if there are performance implications, those won't matter 1.


As a sidenote, so my answer is a bit more complete: the day you'll want to do something like this:

echo "Welcome $names!";

PHP will interpret your code as if you were trying to use the $names variable -- which doesn't exist. - note that it will only work if you use "" not '' for your string.

That day, you'll need to use {}:

echo "Welcome {$name}s!"

No need to fallback to concatenations.


Also note that your first syntax:

echo "Welcome ".$name."!";

Could probably be optimized, avoiding concatenations, using:

echo "Welcome ", $name, "!";

(But, as I said earlier, this doesn't matter much...)


1 - Unless you are doing hundreds of thousands of concatenations vs interpolations -- and it's probably not quite the case.

How to convert a String to CharSequence?

That's a good question! You may get into troubles if you invoke API that uses generics and want to assign or return that result with a different subtype of the generic type. Java 8 helps to transform:

    List<String> input = new LinkedList<>(Arrays.asList("a", "b", "c"));
    List<CharSequence> result;
    
//    result = input; // <-- Type mismatch: cannot convert from List<String> to List<CharSequence>
    result = input.stream().collect(Collectors.toList());
    
    System.out.println(result);

How do I check if a string contains another string in Swift?

You can do this very easily in Swift using the code:

let string = "hello Swift";
let subString = (string as NSString).containsString("Swift")
if(subString){println("Exist")}

Ruby function to remove all white spaces?

" Raheem Shaik ".strip

It will removes left & right side spaces. This code would give us: "Raheem Shaik"

How to select last two characters of a string

The following example uses slice() with negative indexes

_x000D_
_x000D_
var str = 'my name is maanu.';_x000D_
console.log(str.slice(-3));     // returns 'nu.' last two_x000D_
console.log(str.slice(3, -7)); // returns 'name is'_x000D_
console.log(str.slice(0, -1));  // returns 'my name is maanu'
_x000D_
_x000D_
_x000D_

Short rot13 function - Python

The following function rot(s, n) encodes a string s with ROT-n encoding for any integer n, with n defaulting to 13. Both upper- and lowercase letters are supported. Values of n over 26 or negative values are handled appropriately, e.g., shifting by 27 positions is equal to shifting by one position. Decoding is done with invrot(s, n).

import string

def rot(s, n=13):
    '''Encode string s with ROT-n, i.e., by shifting all letters n positions.
    When n is not supplied, ROT-13 encoding is assumed.
    '''
    upper = string.ascii_uppercase
    lower = string.ascii_lowercase
    upper_start = ord(upper[0])
    lower_start = ord(lower[0])
    out = ''
    for letter in s:
        if letter in upper:
            out += chr(upper_start + (ord(letter) - upper_start + n) % 26)
        elif letter in lower:
            out += chr(lower_start + (ord(letter) - lower_start + n) % 26)
        else:
            out += letter
    return(out)

def invrot(s, n=13):
    '''Decode a string s encoded with ROT-n-encoding
    When n is not supplied, ROT-13 is assumed.
    '''
    return(rot(s, -n))

difference between new String[]{} and new String[] in java

1.THE USE OF {}:

It initialize the array with the values { }

2.The difference between String array=new String[]; and String array=new String[]{};

String array=new String[]; and String array=new String[]{}; both are invalid statement in java.

It will gives you an error that you are trying to assign String array to String datatype. More specifically error is like this Type mismatch: cannot convert from String[] to String

3.String array=new String[10]{}; got error why?

Wrong because you are defining an array of length 10 ([10]), then defining an array of length String[10]{} 0

What is the difference between single-quoted and double-quoted strings in PHP?

Some might say that I'm a little off-topic, but here it is anyway:

You don't necessarily have to choose because of your string's content between:
echo "It's \"game\" time."; or echo 'It\'s "game" time.';

If you're familiar with the use of the english quotation marks, and the correct character for the apostrophe, you can use either double or single quotes, because it won't matter anymore:
echo "It’s “game” time."; and echo 'It’s “game” time.';

Of course you can also add variables if needed. Just don't forget that they get evaluated only when in double quotes!

How to copy std::string into std::vector<char>?

std::vector has a constructor that takes two iterators. You can use that:

std::string str = "hello";
std::vector<char> data(str.begin(), str.end());

If you already have a vector and want to add the characters at the end, you need a back inserter:

std::string str = "hello";
std::vector<char> data = /* ... */;
std::copy(str.begin(), str.end(), std::back_inserter(data));

What's the best way to check if a String represents an integer in Java?

How about:

return Pattern.matches("-?\\d+", input);

How can I match a string with a regex in Bash?

if [[ $STR == *pattern* ]]
then
    echo "It is the string!"
else
    echo "It's not him!"
fi

Works for me! GNU bash, version 4.3.11(1)-release (x86_64-pc-linux-gnu)

Fastest method to replace all instances of a character in a string

// Find, Replace, Case
// i.e "Test to see if this works? (Yes|No)".replaceAll('(Yes|No)', 'Yes!');
// i.e.2 "Test to see if this works? (Yes|No)".replaceAll('(yes|no)', 'Yes!', true);
String.prototype.replaceAll = function(_f, _r, _c){ 

  var o = this.toString();
  var r = '';
  var s = o;
  var b = 0;
  var e = -1;
  if(_c){ _f = _f.toLowerCase(); s = o.toLowerCase(); }

  while((e=s.indexOf(_f)) > -1)
  {
    r += o.substring(b, b+e) + _r;
    s = s.substring(e+_f.length, s.length);
    b += e+_f.length;
  }

  // Add Leftover
  if(s.length>0){ r+=o.substring(o.length-s.length, o.length); }

  // Return New String
  return r;
};

Removing spaces from a variable input using PowerShell 4.0

The Replace operator means Replace something with something else; do not be confused with removal functionality.

Also you should send the result processed by the operator to a variable or to another operator. Neither .Replace(), nor -replace modifies the original variable.

To remove all spaces, use 'Replace any space symbol with empty string'

$string = $string -replace '\s',''

To remove all spaces at the beginning and end of the line, and replace all double-and-more-spaces or tab symbols to spacebar symbol, use

$string = $string -replace '(^\s+|\s+$)','' -replace '\s+',' '

or the more native System.String method

$string = $string.Trim()

Regexp is preferred, because ' ' means only 'spacebar' symbol, and '\s' means 'spacebar, tab and other space symbols'. Note that $string.Replace() does 'Normal' replace, and $string -replace does RegEx replace, which is more heavy but more functional.

Note that RegEx have some special symbols like dot (.), braces ([]()), slashes (\), hats (^), mathematical signs (+-) or dollar signs ($) that need do be escaped. ( 'my.space.com' -replace '\.','-' => 'my-space-com'. A dollar sign with a number (ex $1) must be used on a right part with care

'2033' -replace '(\d+)',$( 'Data: $1')
Data: 2033

UPDATE: You can also use $str = $str.Trim(), along with TrimEnd() and TrimStart(). Read more at System.String MSDN page.

C string append

I needed to append substrings to create an ssh command, I solved with sprintf (Visual Studio 2013)

char gStrSshCommand[SSH_COMMAND_MAX_LEN]; // declare ssh command string

strcpy(gStrSshCommand, ""); // empty string

void appendSshCommand(const char *substring) // append substring
{
  sprintf(gStrSshCommand, "%s %s", gStrSshCommand, substring);
}

How do I split a multi-line string into multiple lines?

Might be overkill in this particular case but another option involves using StringIO to create a file-like object

for line in StringIO.StringIO(inputString):
    doStuff()

Converting double to string with N decimals, dot as decimal separator, and no thousand separator

For a decimal, use the ToString method, and specify the Invariant culture to get a period as decimal separator:

value.ToString("0.00", System.Globalization.CultureInfo.InvariantCulture)

The long type is an integer, so there is no fraction part. You can just format it into a string and add some zeros afterwards:

value.ToString() + ".00"

How can I check if a string only contains letters in Python?

Simple:

if string.isalpha():
    print("It's all letters")

str.isalpha() is only true if all characters in the string are letters:

Return true if all characters in the string are alphabetic and there is at least one character, false otherwise.

Demo:

>>> 'hello'.isalpha()
True
>>> '42hello'.isalpha()
False
>>> 'hel lo'.isalpha()
False

What linux shell command returns a part of a string?

In bash you can try this:

stringZ=abcABC123ABCabc
#       0123456789.....
#       0-based indexing.

echo ${stringZ:0:2} # prints ab

More samples in The Linux Documentation Project

How to convert current date into string in java?

String date = new SimpleDateFormat("dd-MM-yyyy").format(new Date());

newline character in c# string

They might be just a \r or a \n. I just checked and the text visualizer in VS 2010 displays both as newlines as well as \r\n.

This string

string test = "blah\r\nblah\rblah\nblah";

Shows up as

blah
blah
blah
blah

in the text visualizer.

So you could try

string modifiedString = originalString
    .Replace(Environment.NewLine, "<br />")
    .Replace("\r", "<br />")
    .Replace("\n", "<br />");

Python - Join with newline

The console is printing the representation, not the string itself.

If you prefix with print, you'll get what you expect.

See this question for details about the difference between a string and the string's representation. Super-simplified, the representation is what you'd type in source code to get that string.

How can I convert a string to upper- or lower-case with XSLT?

<xsl:variable name="upper">UPPER CASE</xsl:variable>
<xsl:variable name="lower" select="translate($upper,'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')"/>
<xsl:value-of select ="$lower"/>

//displays UPPER CASE as upper case

Python TypeError: not enough arguments for format string

Note that the % syntax for formatting strings is becoming outdated. If your version of Python supports it, you should write:

instr = "'{0}', '{1}', '{2}', '{3}', '{4}', '{5}', '{6}'".format(softname, procversion, int(percent), exe, description, company, procurl)

This also fixes the error that you happened to have.

Hex-encoded String to Byte Array

I know it's late but hope it will help someone else...

This is my code: It takes two by two hex representations contained in String and add those into byte array. It works perfectly for me.

public byte[] stringToByteArray (String s) {
    byte[] byteArray = new byte[s.length()/2];
    String[] strBytes = new String[s.length()/2];
    int k = 0;
    for (int i = 0; i < s.length(); i=i+2) {
        int j = i+2;
        strBytes[k] = s.substring(i,j);
        byteArray[k] = (byte)Integer.parseInt(strBytes[k], 16);
        k++;
    }
    return byteArray;
}

Bytes of a string in Java

If you're running with 64-bit references:

sizeof(string) = 
8 + // object header used by the VM
8 + // 64-bit reference to char array (value)
8 + string.length() * 2 + // character array itself (object header + 16-bit chars)
4 + // offset integer
4 + // count integer
4 + // cached hash code

In other words:

sizeof(string) = 36 + string.length() * 2

On a 32-bit VM or a 64-bit VM with compressed OOPs (-XX:+UseCompressedOops), the references are 4 bytes. So the total would be:

sizeof(string) = 32 + string.length() * 2

This does not take into account the references to the string object.

How to convert any Object to String?

"toString()" is Very useful method which returns a string representation of an object. The "toString()" method returns a string reperentation an object.It is recommended that all subclasses override this method.

Declaration: java.lang.Object.toString()

Since, you have not mentioned which object you want to convert, so I am just using any object in sample code.

Integer integerObject = 5;
String convertedStringObject = integerObject .toString();
System.out.println(convertedStringObject );

You can find the complete code here. You can test the code here.

Trim string in JavaScript?

Here's a very simple way:

function removeSpaces(string){
return string.split(' ').join('');
}

How can I use "." as the delimiter with String.split() in java

You might be interested in the StringTokenizer class. However, the java docs advise that you use the .split method as StringTokenizer is a legacy class.

Convert a space delimited string to list

states_list = states.split(' ')

In regards to your edit:

from random import choice
random_state = choice(states_list)

How can I truncate a string to the first 20 words in PHP?

Lets assume we have the string variables $string, $start, and $limit we can borrow 3 or 4 functions from PHP to achieve this. They are:

  • script_tags() PHP function to remove the unnecessary HTML and PHP tags (if there are any). This wont be necessary, if there are no HTML or PHP tags.
  • explode() to split the $string into an array
  • array_splice() to specify the number of words and where it'll start from. It'll be controlled by vallues assigned to our $start and $limit variables.
  • and finally, implode() to join the array elements into your truncated string..

    function truncateString($string, $start, $limit){
        $stripped_string =strip_tags($string); // if there are HTML or PHP tags
        $string_array =explode(' ',$stripped_string);
        $truncated_array = array_splice($string_array,$start,$limit);
        $truncated_string=implode(' ',$truncated_array);
    
        return $truncated_string;
    }
    

It's that simple..

I hope this was helpful.

Read file-contents into a string in C++

There should be no \0 in text files.

#include<iostream>
#include<fstream>

using namespace std;

int main(){
  fstream f(FILENAME, fstream::in );
  string s;
  getline( f, s, '\0');

  cout << s << endl;
  f.close();
}

Javascript string replace with regex to strip off illegal characters

What you need are character classes. In that, you've only to worry about the ], \ and - characters (and ^ if you're placing it straight after the beginning of the character class "[" ).

Syntax: [characters] where characters is a list with characters.

Example:

var cleanString = dirtyString.replace(/[|&;$%@"<>()+,]/g, "");

Rules for C++ string literals escape character

\a is the bell/alert character, which on some systems triggers a sound. \nnn, represents an arbitrary ASCII character in octal base. However, \0 is special in that it represents the null character no matter what.

To answer your original question, you could escape your '0' characters as well, as:

std::string ("\060\000\060", 3);

(since an ASCII '0' is 60 in octal)

The MSDN documentation has a pretty detailed article on this, as well cppreference

Remove final character from string

What you are trying to do is an extension of string slicing in Python:

Say all strings are of length 10, last char to be removed:

>>> st[:9]
'abcdefghi'

To remove last N characters:

>>> N = 3
>>> st[:-N]
'abcdefg'

javascript regular expression to not match a word

if (!s.match(/abc|def/g)) {
    alert("match");
}
else {
    alert("no match");
}

How to test if a string contains one of the substrings in a list, in pandas?

One option is just to use the regex | character to try to match each of the substrings in the words in your Series s (still using str.contains).

You can construct the regex by joining the words in searchfor with |:

>>> searchfor = ['og', 'at']
>>> s[s.str.contains('|'.join(searchfor))]
0    cat
1    hat
2    dog
3    fog
dtype: object

As @AndyHayden noted in the comments below, take care if your substrings have special characters such as $ and ^ which you want to match literally. These characters have specific meanings in the context of regular expressions and will affect the matching.

You can make your list of substrings safer by escaping non-alphanumeric characters with re.escape:

>>> import re
>>> matches = ['$money', 'x^y']
>>> safe_matches = [re.escape(m) for m in matches]
>>> safe_matches
['\\$money', 'x\\^y']

The strings with in this new list will match each character literally when used with str.contains.

CharSequence VS String in Java?

I believe it is best to use CharSequence. The reason is that String implements CharSequence, therefore you can pass a String into a CharSequence, HOWEVER you cannot pass a CharSequence into a String, as CharSequence doesn't not implement String. ALSO, in Android the EditText.getText() method returns an Editable, which also implements CharSequence and can be passed easily into one, while not easily into a String. CharSequence handles all!

String.equals versus ==

Use Split rather than tokenizer,it will surely provide u exact output for E.g:

string name="Harry";
string salary="25000";
string namsal="Harry 25000";
string[] s=namsal.split(" ");
for(int i=0;i<s.length;i++)
{
System.out.println(s[i]);
}
if(s[0].equals("Harry"))
{
System.out.println("Task Complete");
}

After this I am sure you will get better results.....

How to check if a string contains an element from a list in Python

extensionsToCheck = ('.pdf', '.doc', '.xls')

'test.doc'.endswith(extensionsToCheck)   # returns True

'test.jpg'.endswith(extensionsToCheck)   # returns False

Array of strings in groovy

Most of the time you would create a list in groovy rather than an array. You could do it like this:

names = ["lucas", "Fred", "Mary"]

Alternately, if you did not want to quote everything like you did in the ruby example, you could do this:

names = "lucas Fred Mary".split()

How can I get the last 7 characters of a PHP string?

Safer results for working with multibyte character codes, allways use mb_substr instead substr. Example for utf-8:

$str = 'Ne zaman seni düsünsem';
echo substr( $str, -7 ) . ' <strong>is not equal to</strong> ' .
  mb_substr( $str, -7, null, 'UTF-8') ;

Remove file extension from a file name string

You can use

string extension = System.IO.Path.GetExtension(filename);

And then remove the extension manually:

string result = filename.Substring(0, filename.Length - extension.Length);

Parse string to DateTime in C#

The simple and straightforward answer -->

using System;

namespace DemoApp.App

{
public class TestClassDate
{
    public static DateTime GetDate(string string_date)
    {
        DateTime dateValue;
        if (DateTime.TryParse(string_date, out dateValue))
            Console.WriteLine("Converted '{0}' to {1}.", string_date, dateValue);
        else
            Console.WriteLine("Unable to convert '{0}' to a date.", string_date);
        return dateValue;
    }
    public static void Main()
    {
        string inString = "05/01/2009 06:32:00";
        GetDate(inString);
    }
}
}

/**
 * Output:
 * Converted '05/01/2009 06:32:00' to 5/1/2009 6:32:00 AM.
 * */

How to check whether a string contains a substring in JavaScript?

Another alternative is KMP (Knuth–Morris–Pratt).

The KMP algorithm searches for a length-m substring in a length-n string in worst-case O(n+m) time, compared to a worst-case of O(n·m) for the naive algorithm, so using KMP may be reasonable if you care about worst-case time complexity.

Here's a JavaScript implementation by Project Nayuki, taken from https://www.nayuki.io/res/knuth-morris-pratt-string-matching/kmp-string-matcher.js:

// Searches for the given pattern string in the given text string using the Knuth-Morris-Pratt string matching algorithm.
// If the pattern is found, this returns the index of the start of the earliest match in 'text'. Otherwise -1 is returned.

_x000D_
_x000D_
function kmpSearch(pattern, text) {_x000D_
  if (pattern.length == 0)_x000D_
    return 0; // Immediate match_x000D_
_x000D_
  // Compute longest suffix-prefix table_x000D_
  var lsp = [0]; // Base case_x000D_
  for (var i = 1; i < pattern.length; i++) {_x000D_
    var j = lsp[i - 1]; // Start by assuming we're extending the previous LSP_x000D_
    while (j > 0 && pattern.charAt(i) != pattern.charAt(j))_x000D_
      j = lsp[j - 1];_x000D_
    if (pattern.charAt(i) == pattern.charAt(j))_x000D_
      j++;_x000D_
    lsp.push(j);_x000D_
  }_x000D_
_x000D_
  // Walk through text string_x000D_
  var j = 0; // Number of chars matched in pattern_x000D_
  for (var i = 0; i < text.length; i++) {_x000D_
    while (j > 0 && text.charAt(i) != pattern.charAt(j))_x000D_
      j = lsp[j - 1]; // Fall back in the pattern_x000D_
    if (text.charAt(i) == pattern.charAt(j)) {_x000D_
      j++; // Next char matched, increment position_x000D_
      if (j == pattern.length)_x000D_
        return i - (j - 1);_x000D_
    }_x000D_
  }_x000D_
  return -1; // Not found_x000D_
}_x000D_
_x000D_
console.log(kmpSearch('ays', 'haystack') != -1) // true_x000D_
console.log(kmpSearch('asdf', 'haystack') != -1) // false
_x000D_
_x000D_
_x000D_

Case insensitive std::string.find()

You could use std::search with a custom predicate.

#include <locale>
#include <iostream>
#include <algorithm>
using namespace std;

// templated version of my_equal so it could work with both char and wchar_t
template<typename charT>
struct my_equal {
    my_equal( const std::locale& loc ) : loc_(loc) {}
    bool operator()(charT ch1, charT ch2) {
        return std::toupper(ch1, loc_) == std::toupper(ch2, loc_);
    }
private:
    const std::locale& loc_;
};

// find substring (case insensitive)
template<typename T>
int ci_find_substr( const T& str1, const T& str2, const std::locale& loc = std::locale() )
{
    typename T::const_iterator it = std::search( str1.begin(), str1.end(), 
        str2.begin(), str2.end(), my_equal<typename T::value_type>(loc) );
    if ( it != str1.end() ) return it - str1.begin();
    else return -1; // not found
}

int main(int arc, char *argv[]) 
{
    // string test
    std::string str1 = "FIRST HELLO";
    std::string str2 = "hello";
    int f1 = ci_find_substr( str1, str2 );

    // wstring test
    std::wstring wstr1 = L"????? ??????";
    std::wstring wstr2 = L"??????";
    int f2 = ci_find_substr( wstr1, wstr2 );

    return 0;
}

Check if URL has certain string with PHP

This worked for me:

// Check if URL contains the word "car" or "CAR"
   if (stripos($_SERVER['REQUEST_URI'], 'car' )!==false){
   echo "Car here";
   } else {
   echo "No car here";
   }
If you want to use HTML in the echo, be sure to use ' ' instead of " ".
I use this code to show an alert on my webpage https://geaskb.nl/ 
where the URL contains the word "Omnik" 
but hide the alert on pages that do not contain the word "Omnik" in the URL.

Explanation stripos : https://www.php.net/manual/en/function.stripos

How to get character array from a string?

It already is:

_x000D_
_x000D_
var mystring = 'foobar';_x000D_
console.log(mystring[0]); // Outputs 'f'_x000D_
console.log(mystring[3]); // Outputs 'b'
_x000D_
_x000D_
_x000D_

Or for a more older browser friendly version, use:

_x000D_
_x000D_
var mystring = 'foobar';_x000D_
console.log(mystring.charAt(3)); // Outputs 'b'
_x000D_
_x000D_
_x000D_

How can I find whitespace in a String?

public static void main(String[] args) {
    System.out.println("test word".contains(" "));
}

Java: Getting a substring from a string starting after a particular character

This can also get the filename

import java.nio.file.Paths;
import java.nio.file.Path;
Path path = Paths.get("/abc/def/ghfj.doc");
System.out.println(path.getFileName().toString());

Will print ghfj.doc

String comparison: InvariantCultureIgnoreCase vs OrdinalIgnoreCase?

Neither code is always better. They do different things, so they are good at different things.

InvariantCultureIgnoreCase uses comparison rules based on english, but without any regional variations. This is good for a neutral comparison that still takes into account some linguistic aspects.

OrdinalIgnoreCase compares the character codes without cultural aspects. This is good for exact comparisons, like login names, but not for sorting strings with unusual characters like é or ö. This is also faster because there are no extra rules to apply before comparing.

Why does comparing strings using either '==' or 'is' sometimes produce a different result?

is is identity testing and == is equality testing. This means is is a way to check whether two things are the same things, or just equivalent.

Say you've got a simple person object. If it is named 'Jack' and is '23' years old, it's equivalent to another 23-year-old Jack, but it's not the same person.

class Person(object):
   def __init__(self, name, age):
       self.name = name
       self.age = age

   def __eq__(self, other):
       return self.name == other.name and self.age == other.age

jack1 = Person('Jack', 23)
jack2 = Person('Jack', 23)

jack1 == jack2 # True
jack1 is jack2 # False

They're the same age, but they're not the same instance of person. A string might be equivalent to another, but it's not the same object.

C++ -- expected primary-expression before ' '

Change

int wordLength = wordLengthFunction(string word);

to

int wordLength = wordLengthFunction(word);

Check substring exists in a string in C

I believe that I have the simplest answer. You don't need the string.h library in this program, nor the stdbool.h library. Simply using pointers and pointer arithmetic will help you become a better C programmer.

Simply return 0 for False (no substring found), or 1 for True (yes, a substring "sub" is found within the overall string "str"):

#include <stdlib.h>

int is_substr(char *str, char *sub)
{
  int num_matches = 0;
  int sub_size = 0;
  // If there are as many matches as there are characters in sub, then a substring exists.
  while (*sub != '\0') {
    sub_size++;
    sub++;
  }

  sub = sub - sub_size;  // Reset pointer to original place.
  while (*str != '\0') {
    while (*sub == *str && *sub != '\0') {
      num_matches++;
      sub++;
      str++;
    }
    if (num_matches == sub_size) {
      return 1;
    }
    num_matches = 0;  // Reset counter to 0 whenever a difference is found. 
    str++;
  }
  return 0;
}

Java: how to initialize String[]?

You can use below code to initialize size and set empty value to array of Strings

String[] row = new String[size];
Arrays.fill(row, "");

Java Scanner String input

    Scanner ss = new Scanner(System.in);
    System.out.print("Enter the your Name : ");
    // Below Statement used for getting String including sentence
    String s = ss.nextLine(); 
   // Below Statement used for return the first word in the sentence
    String s = ss.next();

What exactly does the .join() method do?

To append a string, just concatenate it with the + sign.

E.g.

>>> a = "Hello, "
>>> b = "world"
>>> str = a + b
>>> print str
Hello, world

join connects strings together with a separator. The separator is what you place right before the join. E.g.

>>> "-".join([a,b])
'Hello, -world'

Join takes a list of strings as a parameter.

How to remove the last character from a string?

removes last occurence of the 'xxx':

    System.out.println("aaa xxx aaa xxx ".replaceAll("xxx([^xxx]*)$", "$1"));

removes last occurrence of the 'xxx' if it is last:

    System.out.println("aaa xxx aaa  ".replaceAll("xxx\\s*$", ""));

you can replace the 'xxx' on what you want but watch out on special chars

Integer to IP Address - C

My alternative solution with subtraction :)

void convert( unsigned int addr )
{    
unsigned int num[OCTET], 
            next_addr[OCTET];

int bits = 8;
unsigned int shift_bits;
int i;

next_addr[0] = addr; 
shift_bits -= bits;  
num[0] = next_addr[0] >> shift_bits;

for ( i = 0; i < OCTET-1; i ++ )
{       
    next_addr[i + 1] = next_addr[i] - ( num[i] << shift_bits ); // next subaddr
    shift_bits -= bits; // next shift
    num[i + 1] = next_addr[i + 1] >> shift_bits; // octet
}

printf( "%d.%d.%d.%d\n", num[0], num[1], num[2], num[3] );
}

How can I convert a comma-separated string to an array?

Shortest

str.split`,`

_x000D_
_x000D_
var str = "January,February,March,April,May,June,July,August,September,October,November,December";_x000D_
_x000D_
let arr = str.split`,`;_x000D_
_x000D_
console.log(arr);
_x000D_
_x000D_
_x000D_

How to split a string between letters and digits (or between digits and letters)?

Use two different patterns: [0-9]* and [a-zA-Z]* and split twice by each of them.

Check whether a string is not null and not empty

test equals with an empty string and null in the same conditional:

if(!"".equals(str) && str != null) {
    // do stuff.
}

Does not throws NullPointerException if str is null, since Object.equals() returns false if arg is null.

the other construct str.equals("") would throw the dreaded NullPointerException. Some might consider bad form using a String literal as the object upon wich equals() is called but it does the job.

Also check this answer: https://stackoverflow.com/a/531825/1532705

How to cut a string after a specific character in unix

Using sed:

$ [email protected]:/home/some/directory/file
$ echo $var | sed 's/.*://'
/home/some/directory/file

Returning string from C function

Easier still: return a pointer to a string that's been malloc'd with strdup.

#include <ncurses.h>

char * getStr(int length)
{   
    char word[length];

    for (int i = 0; i < length; i++)
    {
        word[i] = getch();
    }

    word[i] = '\0';
    return strdup(&word[0]);
}

int main()
{
    char wordd[10];
    initscr();
    *wordd = getStr(10);
    printw("The string is:\n");
    printw("%s\n",*wordd);
    getch();
    endwin();
    return 0;
}

How do I replace a double-quote with an escape-char double-quote in a string using JavaScript?

The other answers will work for most strings, but you can end up unescaping an already escaped double quote, which is probably not what you want.

To work correctly, you are going to need to escape all backslashes and then escape all double quotes, like this:

var test_str = '"first \\" middle \\" last "';
var result = test_str.replace(/\\/g, '\\\\').replace(/\"/g, '\\"');

depending on how you need to use the string, and the other escaped charaters involved, this may still have some issues, but I think it will probably work in most cases.

Generate random string/characters in JavaScript

//creates a random code which is 10 in lenght,you can change it to yours at your will

function createRandomCode(length) {
    let randomCodes = '';
    let characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    let charactersLength = characters.length;
    for (let i = 0; i < length; i++ ) {
        randomCodes += characters.charAt(Math.floor(Math.random() * charactersLength))
    }
    console.log("your reference code is: ".toLocaleUpperCase() + randomCodes);
 };
 createRandomCode(10)

Python: how to print range a-z?

myList = [chr(chNum) for chNum in list(range(ord('a'),ord('z')+1))]
print(myList)

Output

['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

Insert multiple rows WITHOUT repeating the "INSERT INTO ..." part of the statement?

You can use a union:

INSERT INTO dbo.MyTable (ID, Name) 
SELECT ID, Name FROM (
    SELECT 123, 'Timmy'
    UNION ALL
    SELECT 124, 'Jonny'
    UNION ALL
    SELECT 125, 'Sally'
) AS X (ID, Name)

Fork() function in C

System call fork() is used to create processes. It takes no arguments and returns a process ID. The purpose of fork() is to create a new process, which becomes the child process of the caller. After a new child process is created, both processes will execute the next instruction following the fork() system call. Therefore, we have to distinguish the parent from the child. This can be done by testing the returned value of fork()

Fork is a system call and you shouldnt think of it as a normal C function. When a fork() occurs you effectively create two new processes with their own address space.Variable that are initialized before the fork() call store the same values in both the address space. However values modified within the address space of either of the process remain unaffected in other process one of which is parent and the other is child. So if,

pid=fork();

If in the subsequent blocks of code you check the value of pid.Both processes run for the entire length of your code. So how do we distinguish them. Again Fork is a system call and here is difference.Inside the newly created child process pid will store 0 while in the parent process it would store a positive value.A negative value inside pid indicates a fork error.

When we test the value of pid to find whether it is equal to zero or greater than it we are effectively finding out whether we are in the child process or the parent process.

Read more about Fork

What is attr_accessor in Ruby?

Another way to understand it is to figure out what error code it eliminates by having attr_accessor.

Example:

class BankAccount    
  def initialize( account_owner )
    @owner = account_owner
    @balance = 0
  end

  def deposit( amount )
    @balance = @balance + amount
  end

  def withdraw( amount )
    @balance = @balance - amount
  end
end

The following methods are available:

$ bankie = BankAccout.new("Iggy")
$ bankie 
$ bankie.deposit(100)
$ bankie.withdraw(5)

The following methods throws error:

$ bankie.owner     #undefined method `owner'... 
$ bankie.balance   #undefined method `balance'...

owner and balance are not, technically, a method, but an attribute. BankAccount class does not have def owner and def balance. If it does, then you can use the two commands below. But those two methods aren't there. However, you can access attributes as if you'd access a method via attr_accessor!! Hence the word attr_accessor. Attribute. Accessor. It accesses attributes like you would access a method.

Adding attr_accessor :balance, :owner allows you to read and write balance and owner "method". Now you can use the last 2 methods.

$ bankie.balance
$ bankie.owner

How to actually search all files in Visual Studio

One can access the "Find in Files" window via the drop-down menu selection and search all files in the Entire Solution: Edit > Find and Replace > Find in Files

enter image description here

Other, alternative is to open the "Find in Files" window via the "Standard Toolbars" button as highlighted in the below screen-short:

enter image description here

Root password inside a Docker container

You can log into the Docker container using the root user (ID = 0) instead of the provided default user when you use the -u option. E.g.

docker exec -u 0 -it mycontainer bash

root (id = 0) is the default user within a container. The image developer can create additional users. Those users are accessible by name. When passing a numeric ID, the user does not have to exist in the container.

from Docker documentation

Update: Of course you can also use the Docker management command for containers to run this:

docker container exec -u 0 -it mycontainer bash

Can ordered list produce result that looks like 1.1, 1.2, 1.3 (instead of just 1, 2, 3, ...) with css?

this is proper code if you want to first child li resize of other css.

<style>
    li.title { 
        font-size: 20px; 

        counter-increment: ordem; 
        color:#0080B0;
    }
    .my_ol_class { 
        counter-reset: my_ol_class; 
        padding-left: 30px !important; 
    }
    .my_ol_class li { 
          display: block;
        position: relative;

    }
    .my_ol_class li:before { 
        counter-increment: my_ol_class; 
        content: counter(ordem) "." counter(my_ol_class) " "; 
        position: absolute;
        margin-right: 100%;
        right: 10px; /* space between number and text */
    }
    li.title ol li{
         font-size: 15px;
         color:#5E5E5E;
    }
</style>

in html file.

        <ol>
            <li class="title"> <p class="page-header list_title">Acceptance of Terms. </p>
                <ol class="my_ol_class">
                    <li> 
                        <p>
                            my text 1.
                        </p>
                    </li>
                    <li>
                        <p>
                            my text 2.
                        </p>
                    </li>
                </ol>
            </li>
        </ol>

Select from one table matching criteria in another?

select a.id, a.object
from table_A a
inner join table_B b on a.id=b.id
where b.tag = 'chair';

What's the best UI for entering date of birth?

If your goal is to make sure "the user won't be confused at all," I think this is the best option.

three dropdowns for month, day, year

I wouldn't recommend a datepicker for date of birth. First you have to browse to the year (click, click, click…), then to the month (click some more), and then find and click the tiny number on a grid.

Datepickers are useful when you don't know the exact date off the top of your head, e.g. you're planning a trip for the second week of February.

"FATAL: Module not found error" using modprobe

i think there should be entry of your your_module.ko in /lib/modules/uname -r/modules.dep and in /lib/modules/uname -r/modules.dep.bin for "modprobe your_module" command to work

Bogus foreign key constraint fail

On demand, now as an answer...

When using MySQL Query Browser or phpMyAdmin, it appears that a new connection is opened for each query (bugs.mysql.com/bug.php?id=8280), making it neccessary to write all the drop statements in one query, eg.

SET FOREIGN_KEY_CHECKS=0; 
DROP TABLE my_first_table_to_drop; 
DROP TABLE my_second_table_to_drop; 
SET FOREIGN_KEY_CHECKS=1; 

Where the SET FOREIGN_KEY_CHECKS=1 serves as an extra security measure...

Convert string with commas to array

Why don't you do replace , comma and split('') the string like this which will result into ['0', '1'], furthermore, you could wrap the result into parseInt() to transform element into integer type.

it('convert string to array', function () {
  expect('0,1'.replace(',', '').split('')).toEqual(['0','1'])
});

On - window.location.hash - Change?

Ben Alman has a great jQuery plugin for dealing with this: http://benalman.com/projects/jquery-hashchange-plugin/

If you're not using jQuery it may be an interesting reference to dissect.

Infinity symbol with HTML

You can use the following:

  • literal: 8 (if the encoding you use can encode it — UTF-8 can, for example)
  • character reference: &#8734; (decimal), &#x221E; (hexadecimal)
  • entity reference: &infin;

But whether it is displayed correctly does also depend on the font the text is displayed with.

Python list iterator behavior and next(iterator)

I find the existing answers a little confusing, because they only indirectly indicate the essential mystifying thing in the code example: both* the "print i" and the "next(a)" are causing their results to be printed.

Since they're printing alternating elements of the original sequence, and it's unexpected that the "next(a)" statement is printing, it appears as if the "print i" statement is printing all the values.

In that light, it becomes more clear that assigning the result of "next(a)" to a variable inhibits the printing of its' result, so that just the alternate values that the "i" loop variable are printed. Similarly, making the "print" statement emit something more distinctive disambiguates it, as well.

(One of the existing answers refutes the others because that answer is having the example code evaluated as a block, so that the interpreter is not reporting the intermediate values for "next(a)".)

The beguiling thing in answering questions, in general, is being explicit about what is obvious once you know the answer. It can be elusive. Likewise critiquing answers once you understand them. It's interesting...

jQuery Data vs Attr?

The main difference between the two is where it is stored and how it is accessed.

$.fn.attr stores the information directly on the element in attributes which are publicly visible upon inspection, and also which are available from the element's native API.

$.fn.data stores the information in a ridiculously obscure place. It is located in a closed over local variable called data_user which is an instance of a locally defined function Data. This variable is not accessible from outside of jQuery directly.

Data set with attr()

  • accessible from $(element).attr('data-name')
  • accessible from element.getAttribute('data-name'),
  • if the value was in the form of data-name also accessible from $(element).data(name) and element.dataset['name'] and element.dataset.name
  • visible on the element upon inspection
  • cannot be objects

Data set with .data()

  • accessible only from .data(name)
  • not accessible from .attr() or anywhere else
  • not publicly visible on the element upon inspection
  • can be objects

Difference between 'struct' and 'typedef struct' in C++?

You can't use forward declaration with the typedef struct.

The struct itself is an anonymous type, so you don't have an actual name to forward declare.

typedef struct{
    int one;
    int two;
}myStruct;

A forward declaration like this wont work:

struct myStruct; //forward declaration fails

void blah(myStruct* pStruct);

//error C2371: 'myStruct' : redefinition; different basic types

How do I change the figure size for a seaborn plot?

This shall also work.

from matplotlib import pyplot as plt
import seaborn as sns    

plt.figure(figsize=(15,16))
sns.countplot(data=yourdata, ...)

Calculating percentile of dataset column

If you order a vector x, and find the values that is half way through the vector, you just found a median, or 50th percentile. Same logic applies for any percentage. Here are two examples.

x <- rnorm(100)
quantile(x, probs = c(0, 0.25, 0.5, 0.75, 1)) # quartile
quantile(x, probs = seq(0, 1, by= 0.1)) # decile

php - add + 7 days to date format mm dd, YYYY

I would solve this like that. First, I'd create an instance of your given datetime object. Then, I'd create another datetime object which is 7 days later than the initial one. And finally, I'd format it the way you like.

With meringue library, this is quite intuitive and elegant. Here's the code:

(new Future(
    new FromCustomFormat('F j, Y', 'March 3, 2011'),
    new NDays(7)
))
    ->value();

The result is a string in ISO8601 format. If you like, you can format it anyway you like using the same ISO8601 syntax:

(new ISO8601Formatted(
    new Future(
        new FromCustomFormat('F j, Y', 'March 3, 2011'),
        new NDays(7)
    ),
    'F j, Y'
))
    ->value();

The code above uses meringue library. Here's a quick start, you can take a look if you want.

Predicate Delegates in C#

Just a delegate that returns a boolean. It is used a lot in filtering lists but can be used wherever you'd like.

List<DateRangeClass>  myList = new List<DateRangeClass<GetSomeDateRangeArrayToPopulate);
myList.FindAll(x => (x.StartTime <= minDateToReturn && x.EndTime >= maxDateToReturn):

Two decimal places using printf( )

For %d part refer to this How does this program work? and for decimal places use %.2f

How do we use runOnUiThread in Android?

Just wrap it as a function, then call this function from your background thread.

public void debugMsg(String msg) {
    final String str = msg;
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            mInfo.setText(str);
        }
    });
}

curl usage to get header

You need to add the -i flag to the first command, to include the HTTP header in the output. This is required to print headers.

curl -X HEAD -i http://www.google.com

More here: https://serverfault.com/questions/140149/difference-between-curl-i-and-curl-x-head

Why does JavaScript only work after opening developer tools in IE once?

I put the resolution and fix for my issue . Looks like AJAX request that I put inside my JavaScript was not processing because my page was having some cache problem. if your site or page has a caching problem you will not see that problem in developers/F12 mode. my cached JavaScript AJAX requests it may not work as expected and cause the execution to break which F12 has no problem at all. So just added new parameter to make cache false.

$.ajax({
  cache: false,
});

Looks like IE specifically needs this to be false so that the AJAX and javascript activity run well.

Convert boolean to int in Java

int myInt = myBoolean ? 1 : 0;

^^

PS : true = 1 and false = 0

Making an svg image object clickable with onclick, avoiding absolute positioning

If you just use inline svg there is no problem.

_x000D_
_x000D_
<svg id="svg1" xmlns="http://www.w3.org/2000/svg" style="width: 3.5in; height: 1in">_x000D_
  <circle id="circle1" r="30" cx="34" cy="34" onclick="circle1.style.fill='yellow';"_x000D_
            style="fill: red; stroke: blue; stroke-width: 2"/>_x000D_
  </svg>_x000D_
  
_x000D_
_x000D_
_x000D_

Matplotlib tight_layout() doesn't take into account figure suptitle

You can adjust the subplot geometry in the very tight_layout call as follows:

fig.tight_layout(rect=[0, 0.03, 1, 0.95])

As it's stated in the documentation (https://matplotlib.org/users/tight_layout_guide.html):

tight_layout() only considers ticklabels, axis labels, and titles. Thus, other artists may be clipped and also may overlap.

Can't build create-react-app project with custom PUBLIC_URL

This problem becomes apparent when you try to host a react app in github pages.

How I fixed this,

In in my main application file, called app.tsx, where I include the router. I set the basename, eg, <BrowserRouter basename="/Seans-TypeScript-ReactJS-Redux-Boilerplate/">

Note that it is a relative url, this completely simplifies the ability to run locally and hosted. The basename value, matches the repository title on GitHub. This is the path that GitHub pages will auto create.

That is all I needed to do.

See working example hosted on GitHub pages at

https://sean-bradley.github.io/Seans-TypeScript-ReactJS-Redux-Boilerplate/

Fetch: reject promise and catch the error if status is not OK?

Thanks for the help everyone, rejecting the promise in .catch() solved my issue:

export function fetchVehicle(id) {
    return dispatch => {
        return dispatch({
            type: 'FETCH_VEHICLE',
            payload: fetch(`http://swapi.co/api/vehicles/${id}/`)
                .then(status)
                .then(res => res.json())    
                .catch(error => {
                    return Promise.reject()
                })
            });
    };
}


function status(res) {
    if (!res.ok) {
        throw new Error(res.statusText);
    }
    return res;
}

How to get first character of a string in SQL?

I prefer:

SUBSTRING (my_column, 1, 1)

because it is Standard SQL-92 syntax and therefore more portable.


Strictly speaking, the standard version would be

SUBSTRING (my_column FROM 1 FOR 1)

The point is, transforming from one to the other, hence to any similar vendor variation, is trivial.

p.s. It was only recently pointed out to me that functions in standard SQL are deliberately contrary, by having parameters lists that are not the conventional commalists, in order to make them easily identifiable as being from the standard!

How can I use a reportviewer control in an asp.net mvc 3 razor view?

the documentations refers to an ASP.NET application.
You can try and have a look at my answer here.
I have an example attached to my reply.
Another example for ASP.NET MVC3 can be found here.

Submitting the value of a disabled input field

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

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

Angular 4: InvalidPipeArgument: '[object Object]' for pipe 'AsyncPipe'

I found another solution to get the data. according to the documentation Please check documentation link

In service file add following.

import { Injectable } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';

@Injectable()
export class MoviesService {

  constructor(private db: AngularFireDatabase) {}
  getMovies() {
    this.db.list('/movies').valueChanges();
  }
}

In Component add following.

import { Component, OnInit } from '@angular/core';
import { MoviesService } from './movies.service';

@Component({
  selector: 'app-movies',
  templateUrl: './movies.component.html',
  styleUrls: ['./movies.component.css']
})
export class MoviesComponent implements OnInit {
  movies$;

  constructor(private moviesDb: MoviesService) { 
   this.movies$ = moviesDb.getMovies();
 }

In your html file add following.

<li  *ngFor="let m of movies$ | async">{{ m.name }} </li>

Delete the first three rows of a dataframe in pandas

inp0= pd.read_csv("bank_marketing_updated_v1.csv",skiprows=2)

or if you want to do in existing dataframe

simply do following command

How to use setInterval and clearInterval?

setInterval sets up a recurring timer. It returns a handle that you can pass into clearInterval to stop it from firing:

var handle = setInterval(drawAll, 20);

// When you want to cancel it:
clearInterval(handle);
handle = 0; // I just do this so I know I've cleared the interval

On browsers, the handle is guaranteed to be a number that isn't equal to 0; therefore, 0 makes a handy flag value for "no timer set". (Other platforms may return other values; NodeJS's timer functions return an object, for instance.)

To schedule a function to only fire once, use setTimeout instead. It won't keep firing. (It also returns a handle you can use to cancel it via clearTimeout before it fires that one time if appropriate.)

setTimeout(drawAll, 20);

.Net HttpWebRequest.GetResponse() raises exception when http status code 400 (bad request) is returned

An asynchronous version of extension function:

    public static async Task<WebResponse> GetResponseAsyncNoEx(this WebRequest request)
    {
        try
        {
            return await request.GetResponseAsync();
        }
        catch(WebException ex)
        {
            return ex.Response;
        }
    }

Difference between uint32 and uint32_t

uint32_t is defined in the standard, in

18.4.1 Header <cstdint> synopsis [cstdint.syn]

namespace std {
//...
typedef unsigned integer type uint32_t; // optional
//...
}

uint32 is not, it's a shortcut provided by some compilers (probably as typedef uint32_t uint32) for ease of use.

How to top, left justify text in a <td> cell that spans multiple rows

td[rowspan] {
  vertical-align: top;
  text-align: left;
}

See: CSS attribute selectors.

Linking a qtDesigner .ui file to python/pyqt?

Combining Max's answer and Shriramana Sharma's mailing list post, I built a small working example for loading a mywindow.ui file containing a QMainWindow (so just choose to create a Main Window in Qt Designer's File-New dialog).

This is the code that loads it:

import sys
from PyQt4 import QtGui, uic

class MyWindow(QtGui.QMainWindow):
    def __init__(self):
        super(MyWindow, self).__init__()
        uic.loadUi('mywindow.ui', self)
        self.show()

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    window = MyWindow()
    sys.exit(app.exec_())

How to view table contents in Mysql Workbench GUI?

Inside the workbench right click the table in question and click "Select Rows - Limit 1000." It's the first option in the pop-up menu.

Cannot hide status bar in iOS7

Steps For Hide the status bar in iOS 7:

1.Go to your application info.plist file.

2.And Set, View controller-based status bar appearance : Boolean NO

Hope i solved the status bar issue.....

How to change button color with tkinter

When you do self.button = Button(...).grid(...), what gets assigned to self.button is the result of the grid() command, not a reference to the Button object created.

You need to assign your self.button variable before packing/griding it. It should look something like this:

self.button = Button(self,text="Click Me",command=self.color_change,bg="blue")
self.button.grid(row = 2, column = 2, sticky = W)

tooltips for Button

Use title attribute. It is a standard HTML attribute and is by default rendered in a tooltip by most desktop browsers.

How to remove specific session in asp.net?

you can use Session.Remove() method; Session.Remove

Session.Remove("yourSessionName");

Where's the IE7/8/9/10-emulator in IE11 dev tools?

I posted an answer to this already when someone else asked the same question (see How to bring back "Browser mode" in IE11?).

Read my answer there for a fuller explaination, but in short:

  • They removed it deliberately, because compat mode is not actually really very good for testing compatibility.

  • If you really want to test for compatibility with any given version of IE, you need to test in a real copy of that IE version. MS provide free VMs on http://modern.ie/ for you to use for this purpose.

  • The only way to get compat mode in IE11 is to set the X-UA-Compatible header. When you have this and the site defaults to compat mode, you will be able to set the mode in dev tools, but only between edge or the specified compat mode; other modes will still not be available.

Allow multiple roles to access controller action

Another clear solution, you can use constants to keep convention and add multiple [Authorize] attributes. Check this out:

public static class RolesConvention
{
    public const string Administrator = "Administrator";
    public const string Guest = "Guest";
}

Then in the controller:

[Authorize(Roles = RolesConvention.Administrator )]
[Authorize(Roles = RolesConvention.Guest)]
[Produces("application/json")]
[Route("api/[controller]")]
public class MyController : Controller

How do I invert BooleanToVisibilityConverter?

Write your own is the best solution for now. Here is an example of a Converter that can do both way Normal and Inverted. If you have any problems with this just ask.

[ValueConversion(typeof(bool), typeof(Visibility))]
public class InvertableBooleanToVisibilityConverter : IValueConverter
{
    enum Parameters
    {
        Normal, Inverted
    }

    public object Convert(object value, Type targetType,
                          object parameter, CultureInfo culture)
    {
        var boolValue = (bool)value;
        var direction = (Parameters)Enum.Parse(typeof(Parameters), (string)parameter);

        if(direction == Parameters.Inverted)
            return !boolValue? Visibility.Visible : Visibility.Collapsed;

        return boolValue? Visibility.Visible : Visibility.Collapsed;
    }

    public object ConvertBack(object value, Type targetType,
        object parameter, CultureInfo culture)
    {
        return null;
    }
}
<UserControl.Resources>
  <Converters:InvertableBooleanToVisibilityConverter x:Key="_Converter"/>
</UserControl.Resources>

<Button Visibility="{Binding IsRunning, Converter={StaticResource _Converter}, ConverterParameter=Inverted}">Start</Button>

Using ResourceManager

This SO answer might help in this case.
If the main project already references the resource project, then you could just explicitly work with your generated-resource class in your code, and access its ResourceManager from that. Hence, something along the lines of:

ResourceManager resMan = YeagerTechResources.Resources.ResourceManager;

// then, you could go on working with that
ResourceSet resourceSet = resMan.GetResourceSet(CultureInfo.CurrentUICulture, true, true);
// ...

Java using enum with switch statement

Short associative function example:

public String getIcon(TipoNotificacao tipo)
{
    switch (tipo){
        case Comentou : return "fa fa-comments";
        case ConviteEnviou : return "icon-envelope";
        case ConviteAceitou : return "fa fa-bolt";
        default: return "";
    }
}

Like @Dhanushka said, omit the qualifier inside "switch" is the key.

How to convert string values from a dictionary, into int/float datatypes?

If that's your exact format, you can go through the list and modify the dictionaries.

for item in list_of_dicts:
    for key, value in item.iteritems():
        try:
            item[key] = int(value)
        except ValueError:
            item[key] = float(value)

If you've got something more general, then you'll have to do some kind of recursive update on the dictionary. Check if the element is a dictionary, if it is, use the recursive update. If it's able to be converted into a float or int, convert it and modify the value in the dictionary. There's no built-in function for this and it can be quite ugly (and non-pythonic since it usually requires calling isinstance).

Toggle Class in React

refs is not a DOM element. In order to find a DOM element, you need to use findDOMNode menthod first.

Do, this

var node = ReactDOM.findDOMNode(this.refs.btn);
node.classList.toggle('btn-menu-open');

alternatively, you can use like this (almost actual code)

this.state.styleCondition = false;


<a ref="btn" href="#" className={styleCondition ? "btn-menu show-on-small" : ""}><i></i></a>

you can then change styleCondition based on your state change conditions.

R adding days to a date

You could also use

library(lubridate)
dmy("1/1/2001") + days(45)

How to pass multiple parameters in a querystring

I use the AbsoluteUri and you can get it like this:

string myURI = Request.Url.AbsoluteUri;
 if (!WebSecurity.IsAuthenticated) {
        Response.Redirect("~/Login?returnUrl="
            + Request.Url.AbsoluteUri );

Then after you login:

var returnUrl = Request.QueryString["returnUrl"];
 if(WebSecurity.Login(username,password,true)){
                Context.RedirectLocal(returnUrl);

It works well for me.

How do I get a string format of the current date time, in python?

You can use the datetime module for working with dates and times in Python. The strftime method allows you to produce string representation of dates and times with a format you specify.

>>> import datetime
>>> datetime.date.today().strftime("%B %d, %Y")
'July 23, 2010'
>>> datetime.datetime.now().strftime("%I:%M%p on %B %d, %Y")
'10:36AM on July 23, 2010'

Get the short Git version hash

Branch with short hash and last comment:

git branch -v

  develop      717c2f9 [ahead 42] blabla
* master       2722bbe [ahead 1] bla

SQL 'LIKE' query using '%' where the search criteria contains '%'

To escape a character in sql you can use !:


EXAMPLE - USING ESCAPE CHARACTERS

It is important to understand how to "Escape Characters" when pattern matching. These examples deal specifically with escaping characters in Oracle.

Let's say you wanted to search for a % or a _ character in the SQL LIKE condition. You can do this using an Escape character.

Please note that you can only define an escape character as a single character (length of 1).

For example:

SELECT *
FROM suppliers
WHERE supplier_name LIKE '!%' escape '!';

This SQL LIKE condition example identifies the ! character as an escape character. This statement will return all suppliers whose name is %.

Here is another more complicated example using escape characters in the SQL LIKE condition.

SELECT *
FROM suppliers
WHERE supplier_name LIKE 'H%!%' escape '!';

This SQL LIKE condition example returns all suppliers whose name starts with H and ends in %. For example, it would return a value such as 'Hello%'.

You can also use the escape character with the _ character in the SQL LIKE condition.

For example:

SELECT *
FROM suppliers
WHERE supplier_name LIKE 'H%!_' escape '!';

This SQL LIKE condition example returns all suppliers whose name starts with H and ends in _ . For example, it would return a value such as 'Hello_'.


Reference: sql/like

Rails: Adding an index after adding column

For references you can call

rails generate migration AddUserIdColumnToTable user:references

If in the future you need to add a general index you can launch this

rails g migration AddOrdinationNumberToTable ordination_number:integer:index

Generate code:

class AddOrdinationNumberToTable < ActiveRecord::Migration
  def change
   add_column :tables, :ordination_number, :integer
   add_index :tables, :ordination_number, unique: true
  end
end

JavaScript string and number conversion

Simplest is when you want to make a integer a string do

var a,b, c;
a = 1;
b = a.toString(); // This will give you string

Now, from the variable b which is of type string we can get the integer

c = b *1; //This will give you integer value of number :-)

If you want to check above is a number. If you are not sure if b contains integer then you can use

if(isNaN(c*1)) {
  //NOt a number
}
else //number

Switch case with fallthrough?

Use a vertical bar (|) for "or".

case "$C" in
"1")
    do_this()
    ;;
"2" | "3")
    do_what_you_are_supposed_to_do()
    ;;
*)
    do_nothing()
    ;;
esac

What's a concise way to check that environment variables are set in a Unix shell script?

Parameter Expansion

The obvious answer is to use one of the special forms of parameter expansion:

: ${STATE?"Need to set STATE"}
: ${DEST:?"Need to set DEST non-empty"}

Or, better (see section on 'Position of double quotes' below):

: "${STATE?Need to set STATE}"
: "${DEST:?Need to set DEST non-empty}"

The first variant (using just ?) requires STATE to be set, but STATE="" (an empty string) is OK — not exactly what you want, but the alternative and older notation.

The second variant (using :?) requires DEST to be set and non-empty.

If you supply no message, the shell provides a default message.

The ${var?} construct is portable back to Version 7 UNIX and the Bourne Shell (1978 or thereabouts). The ${var:?} construct is slightly more recent: I think it was in System III UNIX circa 1981, but it may have been in PWB UNIX before that. It is therefore in the Korn Shell, and in the POSIX shells, including specifically Bash.

It is usually documented in the shell's man page in a section called Parameter Expansion. For example, the bash manual says:

${parameter:?word}

Display Error if Null or Unset. If parameter is null or unset, the expansion of word (or a message to that effect if word is not present) is written to the standard error and the shell, if it is not interactive, exits. Otherwise, the value of parameter is substituted.

The Colon Command

I should probably add that the colon command simply has its arguments evaluated and then succeeds. It is the original shell comment notation (before '#' to end of line). For a long time, Bourne shell scripts had a colon as the first character. The C Shell would read a script and use the first character to determine whether it was for the C Shell (a '#' hash) or the Bourne shell (a ':' colon). Then the kernel got in on the act and added support for '#!/path/to/program' and the Bourne shell got '#' comments, and the colon convention went by the wayside. But if you come across a script that starts with a colon, now you will know why.


Position of double quotes

blong asked in a comment:

Any thoughts on this discussion? https://github.com/koalaman/shellcheck/issues/380#issuecomment-145872749

The gist of the discussion is:

… However, when I shellcheck it (with version 0.4.1), I get this message:

In script.sh line 13:
: ${FOO:?"The environment variable 'FOO' must be set and non-empty"}
  ^-- SC2086: Double quote to prevent globbing and word splitting.

Any advice on what I should do in this case?

The short answer is "do as shellcheck suggests":

: "${STATE?Need to set STATE}"
: "${DEST:?Need to set DEST non-empty}"

To illustrate why, study the following. Note that the : command doesn't echo its arguments (but the shell does evaluate the arguments). We want to see the arguments, so the code below uses printf "%s\n" in place of :.

$ mkdir junk
$ cd junk
$ > abc
$ > def
$ > ghi
$ 
$ x="*"
$ printf "%s\n" ${x:?You must set x}    # Careless; not recommended
abc
def
ghi
$ unset x
$ printf "%s\n" ${x:?You must set x}    # Careless; not recommended
bash: x: You must set x
$ printf "%s\n" "${x:?You must set x}"  # Careful: should be used
bash: x: You must set x
$ x="*"
$ printf "%s\n" "${x:?You must set x}"  # Careful: should be used
*
$ printf "%s\n" ${x:?"You must set x"}  # Not quite careful enough
abc
def
ghi
$ x=
$ printf "%s\n" ${x:?"You must set x"}  # Not quite careful enough
bash: x: You must set x
$ unset x
$ printf "%s\n" ${x:?"You must set x"}  # Not quite careful enough
bash: x: You must set x
$ 

Note how the value in $x is expanded to first * and then a list of file names when the overall expression is not in double quotes. This is what shellcheck is recommending should be fixed. I have not verified that it doesn't object to the form where the expression is enclosed in double quotes, but it is a reasonable assumption that it would be OK.

Windows command prompt log to a file

In cmd when you use > or >> the output will be only written on the file. Is it possible to see the output in the cmd windows and also save it in a file. Something similar if you use teraterm, when you can start saving all the log in a file meanwhile you use the console and view it (only for ssh, telnet and serial).

Best way to test exceptions with Assert to ensure they will be thrown

With most .net unit testing frameworks you can put an [ExpectedException] attribute on the test method. However this can't tell you that the exception happened at the point you expected it to. That's where xunit.net can help.

With xunit you have Assert.Throws, so you can do things like this:

    [Fact]
    public void CantDecrementBasketLineQuantityBelowZero()
    {
        var o = new Basket();
        var p = new Product {Id = 1, NetPrice = 23.45m};
        o.AddProduct(p, 1);
        Assert.Throws<BusinessException>(() => o.SetProductQuantity(p, -3));
    }

[Fact] is the xunit equivalent of [TestMethod]

Page vs Window in WPF?

Page Control can be contained in Window Control but vice versa is not possible

You can use Page control within the Window control using NavigationWindow and Frame controls. Window is the root control that must be used to hold/host other controls (e.g. Button) as container. Page is a control which can be hosted in other container controls like NavigationWindow or Frame. Page control has its own goal to serve like other controls (e.g. Button). Page is to create browser like applications. So if you host Page in NavigationWindow, you will get the navigation implementation built-in. Pages are intended for use in Navigation applications (usually with Back and Forward buttons, e.g. Internet Explorer).

WPF provides support for browser style navigation inside standalone application using Page class. User can create multiple pages, navigate between those pages along with data.There are multiple ways available to Navigate through one page to another page.

The type 'string' must be a non-nullable type in order to use it as parameter T in the generic type or method 'System.Nullable<T>'

Please note that in upcoming version of C# which is 8, the answers are not true.

All the reference types are non-nullable by default and you can actually do the following:

public string? MyNullableString; 
this.MyNullableString = null; //Valid

However,

public string MyNonNullableString; 
this.MyNonNullableString = null; //Not Valid and you'll receive compiler warning. 

The important thing here is to show the intent of your code. If the "intent" is that the reference type can be null, then mark it so otherwise assigning null value to non-nullable would result in compiler warning.

More info

Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

The code marked @Before is executed before each test, while @BeforeClass runs once before the entire test fixture. If your test class has ten tests, @Before code will be executed ten times, but @BeforeClass will be executed only once.

In general, you use @BeforeClass when multiple tests need to share the same computationally expensive setup code. Establishing a database connection falls into this category. You can move code from @BeforeClass into @Before, but your test run may take longer. Note that the code marked @BeforeClass is run as static initializer, therefore it will run before the class instance of your test fixture is created.

In JUnit 5, the tags @BeforeEach and @BeforeAll are the equivalents of @Before and @BeforeClass in JUnit 4. Their names are a bit more indicative of when they run, loosely interpreted: 'before each tests' and 'once before all tests'.

How do you format a Date/Time in TypeScript?

function _formatDatetime(date: Date, format: string) {
   const _padStart = (value: number): string => value.toString().padStart(2, '0');
return format
    .replace(/yyyy/g, _padStart(date.getFullYear()))
    .replace(/dd/g, _padStart(date.getDate()))
    .replace(/mm/g, _padStart(date.getMonth() + 1))
    .replace(/hh/g, _padStart(date.getHours()))
    .replace(/ii/g, _padStart(date.getMinutes()))
    .replace(/ss/g, _padStart(date.getSeconds()));
}
function isValidDate(d: Date): boolean {
    return !isNaN(d.getTime());
}
export function formatDate(date: any): string {
    var datetime = new Date(date);
    return isValidDate(datetime) ? _formatDatetime(datetime, 'yyyy-mm-dd hh:ii:ss') : '';
}

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

More homegrown appraoch rather than converting authentication / passwords / username to encrytpted details. FTPLIB is just the example. "pass.csv" is the csv file name

Save password in CSV like below :

user_name

user_password

(With no column heading)

Reading the CSV and saving it to a list.

Using List elelments as authetntication details.

Full code.

import os
import ftplib
import csv 
cred_detail = []
os.chdir("Folder where the csv file is stored")
for row in csv.reader(open("pass.csv","rb")):       
        cred_detail.append(row)
ftp = ftplib.FTP('server_name',cred_detail[0][0],cred_detail[1][0])

How to use java.Set

The first thing you need to study is the java.util.Set API.

Here's a small example of how to use its methods:

    Set<Integer> numbers = new TreeSet<Integer>();

    numbers.add(2);
    numbers.add(5);

    System.out.println(numbers); // "[2, 5]"
    System.out.println(numbers.contains(7)); // "false"

    System.out.println(numbers.add(5)); // "false"
    System.out.println(numbers.size()); // "2"

    int sum = 0;
    for (int n : numbers) {
        sum += n;
    }
    System.out.println("Sum = " + sum); // "Sum = 7"

    numbers.addAll(Arrays.asList(1,2,3,4,5));
    System.out.println(numbers); // "[1, 2, 3, 4, 5]"

    numbers.removeAll(Arrays.asList(4,5,6,7));
    System.out.println(numbers); // "[1, 2, 3]"

    numbers.retainAll(Arrays.asList(2,3,4,5));
    System.out.println(numbers); // "[2, 3]"

Once you're familiar with the API, you can use it to contain more interesting objects. If you haven't familiarized yourself with the equals and hashCode contract, already, now is a good time to start.

In a nutshell:

  • @Override both or none; never just one. (very important, because it must satisfied property: a.equals(b) == true --> a.hashCode() == b.hashCode()
    • Be careful with writing boolean equals(Thing other) instead; this is not a proper @Override.
  • For non-null references x, y, z, equals must be:
    • reflexive: x.equals(x).
    • symmetric: x.equals(y) if and only if y.equals(x)
    • transitive: if x.equals(y) && y.equals(z), then x.equals(z)
    • consistent: x.equals(y) must not change unless the objects have mutated
    • x.equals(null) == false
  • The general contract for hashCode is:
    • consistent: return the same number unless mutation happened
    • consistent with equals: if x.equals(y), then x.hashCode() == y.hashCode()
      • strictly speaking, object inequality does not require hash code inequality
      • but hash code inequality necessarily requires object inequality
  • What counts as mutation should be consistent between equals and hashCode.

Next, you may want to impose an ordering of your objects. You can do this by making your type implements Comparable, or by providing a separate Comparator.

Having either makes it easy to sort your objects (Arrays.sort, Collections.sort(List)). It also allows you to use SortedSet, such as TreeSet.


Further readings on stackoverflow:

Achieving white opacity effect in html/css

Try RGBA, e.g.

div { background-color: rgba(255, 255, 255, 0.5); }

As always, this won't work in every single browser ever written.

A SQL Query to select a string between two known strings

You need to adjust for the LENGTH in the SUBSTRING. You were pointing it to the END of the 'ending string'.

Try something like this:

declare @TEXT varchar(200)
declare @ST varchar(200)
declare @EN varchar(200)
set @ST = 'the dog'
set @EN = 'immediately'
set @TEXT = 'All I knew was that the dog had been very bad and required harsh punishment immediately regardless of what anyone else thought.'
SELECT SUBSTRING(@Text, CHARINDEX(@ST, @Text), (CHARINDEX(@EN, @Text)+LEN(@EN))-CHARINDEX(@ST, @Text))

Of course, you may need to adjust it a bit.

Windows batch: call more than one command in a FOR loop?

FOR /r %%X IN (*) DO (ECHO %%X & DEL %%X)

How can I check for "undefined" in JavaScript?

Personally, I always use the following:

var x;
if( x === undefined) {
    //Do something here
}
else {
   //Do something else here
}

The window.undefined property is non-writable in all modern browsers (JavaScript 1.8.5 or later). From Mozilla's documentation: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined, I see this: One reason to use typeof() is that it does not throw an error if the variable has not been defined.

I prefer to have the approach of using

x === undefined 

because it fails and blows up in my face rather than silently passing/failing if x has not been declared before. This alerts me that x is not declared. I believe all variables used in JavaScript should be declared.

How can I solve a connection pool problem between ASP.NET and SQL Server?

I wasn't thinking this was my issue at first but in running through this list I discovered that it didn't cover what my issues was.

My issue was that I had a bug in which it tried to write the same record numerous times using entity framework. It shouldn't have been doing this; it was my bug. Take a look at the data you are writing. My thoughts are that SQL was busy writing a record, possibly locking and creating the timeout. After I fixed the area of code that was attempting to write the record multiple in sequential attempts, the error went away.

how to show lines in common (reverse diff)?

Found this answer on a question listed as a duplicate. I find grep to be more admin-friendly than comm, so if you just want the set of matching lines (useful for comparing CSVs, for instance) simply use

grep -F -x -f file1 file2

or the simplified fgrep version

fgrep -xf file1 file2

Plus, you can use file2* to glob and look for lines in common with multiple files, rather than just two.

Some other handy variations include

  • -n flag to show the line number of each matched line
  • -c to only count the number of lines that match
  • -v to display only the lines in file2 that differ (or use diff).

Using comm is faster, but that speed comes at the expense of having to sort your files first. It isn't very useful as a 'reverse diff'.

Javascript/Jquery to change class onclick?

Just using this will add "mynewclass" to the element with the id myElement and revert it on the next call.

<div id="showhide" class="meta-info" onclick="changeclass(this);">

function changeclass(element) {
    $(element).toggleClass('mynewclass');
}

Or for a slighly more jQuery way (you would run this after the DOM is loaded)

<div id="showhide" class="meta-info">

$('#showhide').click(function() {
    $(this).toggleClass('mynewclass');
});

See a working example of this here: http://jsfiddle.net/S76WN/

SQL Server stored procedure Nullable parameter

You can/should set your parameter to value to DBNull.Value;

if (variable == "")
{
     cmd.Parameters.Add("@Param", SqlDbType.VarChar, 500).Value = DBNull.Value;
}
else
{
     cmd.Parameters.Add("@Param", SqlDbType.VarChar, 500).Value = variable;
}

Or you can leave your server side set to null and not pass the param at all.

Getting the minimum of two values in SQL

I just had a situation where I had to find the max of 4 complex selects within an update. With this approach you can have as many as you like!

You can also replace the numbers with aditional selects

select max(x)
 from (
 select 1 as 'x' union
 select 4 as 'x' union
 select 3 as 'x' union
 select 2 as 'x' 
 ) a

More complex usage

 @answer = select Max(x)
           from (
                select @NumberA as 'x' union
                select @NumberB as 'x' union
                select @NumberC as 'x' union
                select (
                       Select Max(score) from TopScores
                       ) as 'x' 
     ) a

I'm sure a UDF has better performance.

How to redirect siteA to siteB with A or CNAME records

It's probably best/easiest to set up a 301 redirect. No DNS hacking required.

SSL Error: CERT_UNTRUSTED while using npm command

You can bypass https using below commands:

npm config set strict-ssl false

or set the registry URL from https or http like below:

npm config set registry="http://registry.npmjs.org/"

However, Personally I believe bypassing https is not the real solution, but we can use it as a workaround.

Add new column with foreign key constraint in one command

If you also need to add default values in case you already have some rows in the table then add DEFAULT val

ALTER TABLE one
ADD two_id int DEFAULT 123,
FOREIGN KEY(two_id) REFERENCES two(id);

How to detect if user select cancel InputBox VBA Excel

Following example uses InputBox method to validate user entry to unhide sheets: Important thing here is to use wrap InputBox variable inside StrPtr so it could be compared to '0' when user chose to click 'x' icon on the InputBox.

Sub unhidesheet()

Dim ws As Worksheet
Dim pw As String

pw = InputBox("Enter Password to Unhide Sheets:", "Unhide Data Sheets")
If StrPtr(pw) = 0 Then

   Exit Sub
ElseIf pw = NullString Then
   Exit Sub
ElseIf pw = 123456 Then
    For Each ws In ThisWorkbook.Worksheets
        ws.Visible = xlSheetVisible
    Next
End If
End Sub

Issue with background color and Google Chrome

I was able to fix this with:

html { height: 100%; }

Xcode: Could not locate device support files

I have Xcode 10.1 and I can not run my application on my device with 12.2 iOS version.

The easiest solution for me was:

  1. Go with finder at Xcode location
  2. Right Click -> Show Package Contents
  3. Contents -> Developer -> Platforms -> iPhoneOS.platform -> DeviceSupport
  4. Here you find a list of supported version. Choose the most recent one and copy(In my case was 12.1 (16B91))
  5. Paste in the same folder(DeviceSupport) and call it with the version you need.(In my case was 12.2 (16E227))
  6. Close Xcode if you have it open
  7. Reconnect device if it was connected
  8. Open Xcode and build

If this trick does not working, you have to get the versions from the new Xcode version.

But you can try, saves a lot of time. Good luck!

EDIT: Or you can download your needed device support from here: https://github.com/iGhibli/iOS-DeviceSupport/tree/master/DeviceSupport

Does file_get_contents() have a timeout setting?

For me work when i change my php.ini in my host:

; Default timeout for socket based streams (seconds)
default_socket_timeout = 300

Does my application "contain encryption"?

Found some of these answers very useful, but wanted to add this URL for completeness since it walks you through the questions:

https://itunespartner.apple.com/en/apps/faq/Managing%20Your%20Apps_Export%20Compliance#21109148

switch() statement usage

Well, timing to the rescue again. It seems switch is generally faster than if statements. So that, and the fact that the code is shorter/neater with a switch statement leans in favor of switch:

# Simplified to only measure the overhead of switch vs if

test1 <- function(type) {
 switch(type,
        mean = 1,
        median = 2,
        trimmed = 3)
}

test2 <- function(type) {
 if (type == "mean") 1
 else if (type == "median") 2
 else if (type == "trimmed") 3
}

system.time( for(i in 1:1e6) test1('mean') ) # 0.89 secs
system.time( for(i in 1:1e6) test2('mean') ) # 1.13 secs
system.time( for(i in 1:1e6) test1('trimmed') ) # 0.89 secs
system.time( for(i in 1:1e6) test2('trimmed') ) # 2.28 secs

Update With Joshua's comment in mind, I tried other ways to benchmark. The microbenchmark seems the best. ...and it shows similar timings:

> library(microbenchmark)
> microbenchmark(test1('mean'), test2('mean'), times=1e6)
Unit: nanoseconds
           expr  min   lq median   uq      max
1 test1("mean")  709  771    864  951 16122411
2 test2("mean") 1007 1073   1147 1223  8012202

> microbenchmark(test1('trimmed'), test2('trimmed'), times=1e6)
Unit: nanoseconds
              expr  min   lq median   uq      max
1 test1("trimmed")  733  792    843  944 60440833
2 test2("trimmed") 2022 2133   2203 2309 60814430

Final Update Here's showing how versatile switch is:

switch(type, case1=1, case2=, case3=2.5, 99)

This maps case2 and case3 to 2.5 and the (unnamed) default to 99. For more information, try ?switch

Fastest way to find second (third...) highest/lowest value in vector or column

Slightly slower alternative, just for the records:

x <- c(12.45,34,4,0,-234,45.6,4)
max( x[x!=max(x)] )
min( x[x!=min(x)] )

Remove Primary Key in MySQL

I had same problem and beside some values inside my table. Although I changed my Primary Key with

ALTER TABLEuser_customer_permissionDROP PRIMARY KEY , ADD PRIMARY KEY (id)

problem continued on my server. I created new field inside the table I transfered the values into new field and deleted old one, problem solved!!

How to perform string interpolation in TypeScript?

In JavaScript you can use template literals:

let value = 100;
console.log(`The size is ${ value }`);

How to select element using XPATH syntax on Selenium for Python?

Check this blog by Martin Thoma. I tested the below code on MacOS Mojave and it worked as specified.

> def get_browser():
>     """Get the browser (a "driver")."""
>     # find the path with 'which chromedriver'
>     path_to_chromedriver = ('/home/moose/GitHub/algorithms/scraping/'
>                             'venv/bin/chromedriver')
>     download_dir = "/home/moose/selenium-download/"
>     print("Is directory: {}".format(os.path.isdir(download_dir)))
> 
>     from selenium.webdriver.chrome.options import Options
>     chrome_options = Options()
>     chrome_options.add_experimental_option('prefs', {
>         "plugins.plugins_list": [{"enabled": False,
>                                   "name": "Chrome PDF Viewer"}],
>         "download": {
>             "prompt_for_download": False,
>             "default_directory": download_dir
>         }
>     })
> 
>     browser = webdriver.Chrome(path_to_chromedriver,
>                                chrome_options=chrome_options)
>     return browser

Order columns through Bootstrap4

I'm using Bootstrap 3, so i don't know if there is an easier way to do it Bootstrap 4 but this css should work for you:

.pull-right-xs {
    float: right;
}

@media (min-width: 768px) {
   .pull-right-xs {
      float: left;
   }
}

...and add class to second column:

<div class="row">
    <div class="col-xs-3 col-md-6">
        1
    </div>
    <div class="col-xs-3 col-md-6 pull-right-xs">
        2
    </div>
    <div class="col-xs-6 col-md-12">
        3
    </div>
</div>

EDIT:

Ohh... it looks like what i was writen above is exacly a .pull-xs-right class in Bootstrap 4 :X Just add it to second column and it should work perfectly.

How to validate phone numbers using regex

I found this to work quite well:

^\(*\+*[1-9]{0,3}\)*-*[1-9]{0,3}[-. /]*\(*[2-9]\d{2}\)*[-. /]*\d{3}[-. /]*\d{4} *e*x*t*\.* *\d{0,4}$

It works for these number formats:

1-234-567-8901
1-234-567-8901 x1234
1-234-567-8901 ext1234
1 (234) 567-8901
1.234.567.8901
1/234/567/8901
12345678901
1-234-567-8901 ext. 1234
(+351) 282 433 5050

Make sure to use global AND multiline flags to make sure.

Link: http://www.regexr.com/3bp4b

JavaFX and OpenJDK

According to Oracle integration of OpenJDK & javaFX will be on Q1-2014 ( see roadmap : http://www.oracle.com/technetwork/java/javafx/overview/roadmap-1446331.html ). So, for the 1st question the answer is that you have to wait until then. For the 2nd question there is no other way. So, for now go with java swing or start javaFX and wait

Conversion of a varchar data type to a datetime data type resulted in an out-of-range value in SQL query

Try ISDATE() function in SQL Server. If 1, select valid date. If 0 selects invalid dates.

SELECT cast(CONVERT(varchar, LoginTime, 101) as datetime)  
FROM AuditTrail 
WHERE ISDATE(LoginTime) = 1

EDIT :

As per your update i need to extract the date only and remove the time, then you could simply use the inner CONVERT

SELECT CONVERT(VARCHAR, LoginTime, 101) FROM AuditTrail 

or

SELECT LEFT(LoginTime,10) FROM AuditTrail

EDIT 2 :

The major reason for the error will be in your date in WHERE clause.ie,

SELECT cast(CONVERT(varchar, LoginTime, 101) as datetime)  
FROM AuditTrail
where CAST(CONVERT(VARCHAR, LoginTime, 101) AS DATE) <= 
CAST('06/18/2012' AS DATE)

will be different from

SELECT cast(CONVERT(varchar, LoginTime, 101) as datetime)  
FROM AuditTrail
where CAST(CONVERT(VARCHAR, LoginTime, 101) AS DATE) <= 
CAST('18/06/2012' AS DATE)

CONCLUSION

In EDIT 2 the first query tries to filter in mm/dd/yyyy format, while the second query tries to filter in dd/mm/yyyy format. Either of them will fail and throws error

The conversion of a varchar data type to a datetime data type resulted in an out-of-range value.

So please make sure to filter date either with mm/dd/yyyy or with dd/mm/yyyy format, whichever works in your db.

How do I convert special UTF-8 chars to their iso-8859-1 equivalent using javascript?

Actually, everything is typically stored as Unicode of some kind internally, but lets not go into that. I'm assuming you're getting the iconic "åäö" type strings because you're using an ISO-8859 as your character encoding. There's a trick you can do to convert those characters. The escape and unescape functions used for encoding and decoding query strings are defined for ISO characters, whereas the newer encodeURIComponent and decodeURIComponent which do the same thing, are defined for UTF8 characters.

escape encodes extended ISO-8859-1 characters (UTF code points U+0080-U+00ff) as %xx (two-digit hex) whereas it encodes UTF codepoints U+0100 and above as %uxxxx (%u followed by four-digit hex.) For example, escape("å") == "%E5" and escape("?") == "%u3042".

encodeURIComponent percent-encodes extended characters as a UTF8 byte sequence. For example, encodeURIComponent("å") == "%C3%A5" and encodeURIComponent("?") == "%E3%81%82".

So you can do:

fixedstring = decodeURIComponent(escape(utfstring));

For example, an incorrectly encoded character "å" becomes "Ã¥". The command does escape("Ã¥") == "%C3%A5" which is the two incorrect ISO characters encoded as single bytes. Then decodeURIComponent("%C3%A5") == "å", where the two percent-encoded bytes are being interpreted as a UTF8 sequence.

If you'd need to do the reverse for some reason, that works too:

utfstring = unescape(encodeURIComponent(originalstring));

Is there a way to differentiate between bad UTF8 strings and ISO strings? Turns out there is. The decodeURIComponent function used above will throw an error if given a malformed encoded sequence. We can use this to detect with a great probability whether our string is UTF8 or ISO.

var fixedstring;

try{
    // If the string is UTF-8, this will work and not throw an error.
    fixedstring=decodeURIComponent(escape(badstring));
}catch(e){
    // If it isn't, an error will be thrown, and we can assume that we have an ISO string.
    fixedstring=badstring;
}

Understanding the set() function

After reading the other answers, I still had trouble understanding why the set comes out un-ordered.

Mentioned this to my partner and he came up with this metaphor: take marbles. You put them in a tube a tad wider than marble width : you have a list. A set, however, is a bag. Even though you feed the marbles one-by-one into the bag; when you pour them from a bag back into the tube, they will not be in the same order (because they got all mixed up in a bag).

Compare object instances for equality by their attributes

Depending on your specific case, you could do:

>>> vars(x) == vars(y)
True

See Python dictionary from an object's fields

Check if table exists

You can use the available meta data:

  DatabaseMetaData meta = con.getMetaData();
  ResultSet res = meta.getTables(null, null, "My_Table_Name", 
     new String[] {"TABLE"});
  while (res.next()) {
     System.out.println(
        "   "+res.getString("TABLE_CAT") 
       + ", "+res.getString("TABLE_SCHEM")
       + ", "+res.getString("TABLE_NAME")
       + ", "+res.getString("TABLE_TYPE")
       + ", "+res.getString("REMARKS")); 
  }

See here for more details. Note also the caveats in the JavaDoc.

Remove json element

As described by @mplungjan, I though it was right. Then right away I click the up rate button. But by following it, I finally got an error.

<script>
var data = {"result":[
  {"FirstName":"Test1","LastName":"User","Email":"[email protected]","City":"ahmedabad","State":"sk","Country":"canada","Status":"False","iUserID":"23"},
  {"FirstName":"user","LastName":"user","Email":"[email protected]","City":"ahmedabad","State":"Gujarat","Country":"India","Status":"True","iUserID":"41"},
  {"FirstName":"Ropbert","LastName":"Jones","Email":"[email protected]","City":"NewYork","State":"gfg","Country":"fgdfgdfg","Status":"True","iUserID":"48"},
  {"FirstName":"hitesh","LastName":"prajapti","Email":"[email protected]","City":"","State":"","Country":"","Status":"True","iUserID":"78"}
  ]
}
alert(data.result)
delete data.result[3]
alert(data.result)
</script>

Delete is just remove the data, but the 'place' is still there as undefined.

I did this and it works like a charm :

data.result.splice(2,1);  

meaning : delete 1 item at position 3 ( because array is counted form 0, then item at no 3 is counted as no 2 )

Calling a function within a Class method?

Try this one:

class test {
     public function newTest(){
          $this->bigTest();
          $this->smallTest();
     }

     private function bigTest(){
          //Big Test Here
     }

     private function smallTest(){
          //Small Test Here
     }

     public function scoreTest(){
          //Scoring code here;
     }
}

$testObject = new test();

$testObject->newTest();

$testObject->scoreTest();

What's the location of the JavaFX runtime JAR file, jfxrt.jar, on Linux?

On Ubuntu with OpenJDK, it installed in /usr/lib/jvm/default-java/jre/lib/ext/jfxrt.jar (technically its a symlink to /usr/share/java/openjfx/jre/lib/ext/jfxrt.jar, but it is probably better to use the default-java link)

Find and Replace string in all files recursive using grep and sed

As @Didier said, you can change your delimiter to something other than /:

grep -rl $oldstring /path/to/folder | xargs sed -i s@$oldstring@$newstring@g

How to encrypt and decrypt file in Android?

Use a CipherOutputStream or CipherInputStream with a Cipher and your FileInputStream / FileOutputStream.

I would suggest something like Cipher.getInstance("AES/CBC/PKCS5Padding") for creating the Cipher class. CBC mode is secure and does not have the vulnerabilities of ECB mode for non-random plaintexts. It should be present in any generic cryptographic library, ensuring high compatibility.

Don't forget to use a Initialization Vector (IV) generated by a secure random generator if you want to encrypt multiple files with the same key. You can prefix the plain IV at the start of the ciphertext. It is always exactly one block (16 bytes) in size.

If you want to use a password, please make sure you do use a good key derivation mechanism (look up password based encryption or password based key derivation). PBKDF2 is the most commonly used Password Based Key Derivation scheme and it is present in most Java runtimes, including Android. Note that SHA-1 is a bit outdated hash function, but it should be fine in PBKDF2, and does currently present the most compatible option.

Always specify the character encoding when encoding/decoding strings, or you'll be in trouble when the platform encoding differs from the previous one. In other words, don't use String.getBytes() but use String.getBytes(StandardCharsets.UTF_8).

To make it more secure, please add cryptographic integrity and authenticity by adding a secure checksum (MAC or HMAC) over the ciphertext and IV, preferably using a different key. Without an authentication tag the ciphertext may be changed in such a way that the change cannot be detected.

Be warned that CipherInputStream may not report BadPaddingException, this includes BadPaddingException generated for authenticated ciphers such as GCM. This would make the streams incompatible and insecure for these kind of authenticated ciphers.

How can I get my Android device country code without using GPS?

You can simply use this code,

TelephonyManager tm = (TelephonyManager)this.getSystemService(Context.TELEPHONY_SERVICE);
String countryCodeValue = tm.getNetworkCountryIso();

This will return 'US' if your current connected network is in the United States. This works without a SIM card even.

ipynb import another ipynb file

The above mentioned comments are very useful but they are a bit difficult to implement. Below steps you can try, I also tried it and it worked:

  1. Download that file from your notebook in PY file format (You can find that option in File tab).
  2. Now copy that downloaded file into the working directory of Jupyter Notebook
  3. You are now ready to use it. Just import .PY File into the ipynb file

json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

I had similar error: "Expecting value: line 1 column 1 (char 0)"

It helped for me to add "myfile.seek(0)", move the pointer to the 0 character

with open(storage_path, 'r') as myfile:
if len(myfile.readlines()) != 0:
    myfile.seek(0)
    Bank_0 = json.load(myfile)

How to calculate the number of occurrence of a given character in each row of a column of strings?

Yet another base R option could be:

lengths(lapply(q.data$string, grepRaw, pattern = "a", all = TRUE, fixed = TRUE))

[1] 2 1 0

How can I find the maximum value and its index in array in MATLAB?

3D case

Modifying Mohsen's answer for 3D array:

[M,I] = max (A(:));
[ind1, ind2, ind3] = ind2sub(size(A),I)

List of lists into numpy array

It's as simple as:

>>> lists = [[1, 2], [3, 4]]
>>> np.array(lists)
array([[1, 2],
       [3, 4]])

Is it possible to use global variables in Rust?

Heap allocations are possible for static variables if you use the lazy_static macro as seen in the docs

Using this macro, it is possible to have statics that require code to be executed at runtime in order to be initialized. This includes anything requiring heap allocations, like vectors or hash maps, as well as anything that requires function calls to be computed.

// Declares a lazily evaluated constant HashMap. The HashMap will be evaluated once and
// stored behind a global static reference.

use lazy_static::lazy_static;
use std::collections::HashMap;

lazy_static! {
    static ref PRIVILEGES: HashMap<&'static str, Vec<&'static str>> = {
        let mut map = HashMap::new();
        map.insert("James", vec!["user", "admin"]);
        map.insert("Jim", vec!["user"]);
        map
    };
}

fn show_access(name: &str) {
    let access = PRIVILEGES.get(name);
    println!("{}: {:?}", name, access);
}

fn main() {
    let access = PRIVILEGES.get("James");
    println!("James: {:?}", access);

    show_access("Jim");
}

jQuery addClass onClick

$('#button').click(function(){
    $(this).addClass('active');
});

Select entries between dates in doctrine 2

I believe the correct way of doing it would be to use query builder expressions:

$now = new DateTimeImmutable();
$thirtyDaysAgo = $now->sub(new \DateInterval("P30D"));
$qb->select('e')
   ->from('Entity','e')
   ->add('where', $qb->expr()->between(
            'e.datefield',
            ':from',
            ':to'
        )
    )
   ->setParameters(array('from' => $thirtyDaysAgo, 'to' => $now));

http://docs.doctrine-project.org/en/latest/reference/query-builder.html#the-expr-class

Edit: The advantage this method has over any of the other answers here is that it's database software independent - you should let Doctrine handle the date type as it has an abstraction layer for dealing with this sort of thing.

If you do something like adding a string variable in the form 'Y-m-d' it will break when it goes to a database platform other than MySQL, for example.

Check If array is null or not in php

This checks if the array is empty

if (!empty($result) {
    // do stuf if array is not empty
} else {
    // do stuf if array is empty
}

This checks if the array is null or not

if (is_null($result) {
   // do stuf if array is null
} else {
   // do stuf if array is not null
}

Serialize Class containing Dictionary member

Instead of using XmlSerializer you can use a System.Runtime.Serialization.DataContractSerializer. This can serialize dictionaries and interfaces no sweat.

Here is a link to a full example, http://theburningmonk.com/2010/05/net-tips-xml-serialize-or-deserialize-dictionary-in-csharp/

How to detect Ctrl+V, Ctrl+C using JavaScript?

I wrote a jQuery plugin, which catches keystrokes. It can be used to enable multiple language script input in html forms without the OS (except the fonts). Its about 300 lines of code, maybe you like to take a look:

Generally, be careful with such kind of alterations. I wrote the plugin for a client because other solutions weren't available.

How to bundle vendor scripts separately and require them as needed with Webpack?

Also not sure if I fully understand your case, but here is config snippet to create separate vendor chunks for each of your bundles:

entry: {
  bundle1: './build/bundles/bundle1.js',
  bundle2: './build/bundles/bundle2.js',
  'vendor-bundle1': [
    'react',
    'react-router'
  ],
  'vendor-bundle2': [
    'react',
    'react-router',
    'flummox',
    'immutable'
  ]
},

plugins: [
  new webpack.optimize.CommonsChunkPlugin({
    name: 'vendor-bundle1',
    chunks: ['bundle1'],
    filename: 'vendor-bundle1.js',
    minChunks: Infinity
  }),
  new webpack.optimize.CommonsChunkPlugin({
    name: 'vendor-bundle2',
    chunks: ['bundle2'],
    filename: 'vendor-bundle2-whatever.js',
    minChunks: Infinity
  }),
]

And link to CommonsChunkPlugin docs: http://webpack.github.io/docs/list-of-plugins.html#commonschunkplugin

500 internal server error at GetResponse()

In my case I just remove the SoapAction instruction from the HttpWebRequest object. So, I don't define .Headers.Add("SOAPAction","someurl") in HttpWebRequest definitions and my code works fine.

ResultXML is an XDocument. ResultString is a string.

try
{
    HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Url);
    //req.Headers.Add("SOAPAction", "http://tempuri.org/IWebService/GetMessage");
    req.ProtocolVersion = HttpVersion.Version11;
    req.ContentType = "text/xml;charset=\"utf-8\"";
    req.Accept = "text/xml";
    req.KeepAlive = true;
    req.Method = "POST";        

    using (Stream stm = req.GetRequestStream())
    {
        using (StreamWriter stmw = new StreamWriter(stm))
            stmw.Write(soapStr);
    }
    using (StreamReader responseReader = new StreamReader(req.GetResponse().GetResponseStream()))
    {
        string result = responseReader.ReadToEnd();
        ResultXML = XDocument.Parse(result);
        ResultString = result;      
    }
}

input type=file show only button

I used some of the code recommended above and after many hours of waisting my time, I eventually came to a css bag free solution.

You can run it over here - http://jsfiddle.net/WqGph/

but then found a better solution - http://jsfiddle.net/XMMc4/5/

 <input type = "button" value = "Choose image #2" 
   onclick ="javascript:document.getElementById('imagefile').click();">
       <input id = "imagefile" type="file" style='display:none;' name="img" value="none"/>see jsfiddle code for examples<br/>

How to detect duplicate values in PHP array?

if(count(array_unique($array))<count($array))
{
    // Array has duplicates
}
else
{
    // Array does not have duplicates
}

How to remove leading and trailing zeros in a string? Python

Assuming you have other data types (and not only string) in your list try this. This removes trailing and leading zeros from strings and leaves other data types untouched. This also handles the special case s = '0'

e.g

a = ['001', '200', 'akdl00', 200, 100, '0']

b = [(lambda x: x.strip('0') if isinstance(x,str) and len(x) != 1 else x)(x) for x in a]

b
>>>['1', '2', 'akdl', 200, 100, '0']

How to place a div below another div?

You have set #slider as absolute, which means that it "is positioned relative to the nearest positioned ancestor" (confusing, right?). Meanwhile, #content div is placed relative, which means "relative to its normal position". So the position of the 2 divs is not related.

You can read about CSS positioning here

If you set both to relative, the divs will be one after the other, as shown here:

#slider {
    position:relative;
    left:0;
    height:400px;

    border-style:solid;
    border-width:5px;
}
#slider img {
    width:100%;
}

#content {
    position:relative;
}

#content #text {
    position:relative;
    width:950px;
    height:215px;
    color:red;
}

http://jsfiddle.net/uorgj4e1/

How to copy a folder via cmd?

xcopy  "C:\Documents and Settings\user\Desktop\?????????" "D:\Backup" /s /e /y /i

Probably the problem is the space.Try with quotes.

Calculating the angle between the line defined by two points

Had a need for similar functionality myself, so after much hair pulling I came up with the function below

/**
 * Fetches angle relative to screen centre point
 * where 3 O'Clock is 0 and 12 O'Clock is 270 degrees
 * 
 * @param screenPoint
 * @return angle in degress from 0-360.
 */
public double getAngle(Point screenPoint) {
    double dx = screenPoint.getX() - mCentreX;
    // Minus to correct for coord re-mapping
    double dy = -(screenPoint.getY() - mCentreY);

    double inRads = Math.atan2(dy, dx);

    // We need to map to coord system when 0 degree is at 3 O'clock, 270 at 12 O'clock
    if (inRads < 0)
        inRads = Math.abs(inRads);
    else
        inRads = 2 * Math.PI - inRads;

    return Math.toDegrees(inRads);
}

How do I create a message box with "Yes", "No" choices and a DialogResult?

MessageBox.Show(title, text, messageboxbuttons.yes/no)

This returns a DialogResult which you can check.

For example,

if(MessageBox.Show("","",MessageBoxButtons.YesNo) == DialogResult.Yes)
{
   //do something
}

How to delete a selected DataGridViewRow and update a connected database table?

maybe you can use temp list for delete. for ignore row index change

_x000D_
_x000D_
<pre>_x000D_
private void btnDelete_Click(object sender, EventArgs e)_x000D_
{_x000D_
    List<int> wantdel = new List<int>();_x000D_
    foreach (DataGridViewRow row in dataGridView1.Rows)_x000D_
    {_x000D_
        if ((bool)row.Cells["Select"].Value == true)_x000D_
        wantdel.Add(row.Index);_x000D_
    }_x000D_
_x000D_
    wantdel.OrderByDescending(y => y).ToList().ForEach(x =>_x000D_
    {_x000D_
        dataGridView1.Rows.RemoveAt(x);_x000D_
    });           _x000D_
}_x000D_
</pre>
_x000D_
_x000D_
_x000D_

No log4j2 configuration file found. Using default configuration: logging only errors to the console

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
<Appenders>
<Console name="Console" target="SYSTEM_OUT">
  <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
</Console>
</Appenders>
<Loggers>
<Root level="DEBUG">
  <AppenderRef ref="Console"/>
</Root>
</Loggers>
</Configuration>
  1. Create a new Text document and copy-paste the above code and save it as log4j2.xml.

  2. Now copy this log4j2.xml file and paste it under your src folder of your Java project.

  3. Run your java program again, you will see error is gone.

Multiple WHERE Clauses with LINQ extension methods

Just use the && operator like you would with any other statement that you need to do boolean logic.

if (useAdditionalClauses)
{
  results = results.Where(
                  o => o.OrderStatus == OrderStatus.Open 
                  && o.CustomerID == customerID)     
}

PLS-00103: Encountered the symbol "CREATE"

Run package declaration and body separately.

What is HTML5 ARIA?

What is ARIA?

ARIA emerged as a way to address the accessibility problem of using a markup language intended for documents, HTML, to build user interfaces (UI). HTML includes a great many features to deal with documents (P, h3,UL,TABLE) but only basic UI elements such as A, INPUT and BUTTON. Windows and other operating systems support APIs that allow (Assistive Technology) AT to access the functionality of UI controls. Internet Explorer and other browsers map the native HTML elements to the accessibility API, but the html controls are not as rich as the controls common on desktop operating systems, and are not enough for modern web applications Custom controls can extend html elements to provide the rich UI needed for modern web applications. Before ARIA, the browser had no way to expose this extra richness to the accessibility API or AT. The classic example of this issue is adding a click handler to an image. It creates what appears to be a clickable button to a mouse user, but is still just an image to a keyboard or AT user.

The solution was to create a set of attributes that allow developers to extend HTML with UI semantics. The ARIA term for a group of HTML elements that have custom functionality and use ARIA attributes to map these functions to accessibility APIs is a “Widget. ARIA also provides a means for authors to document the role of content itself, which in turn, allows AT to construct alternate navigation mechanisms for the content that are much easier to use than reading the full text or only iterating over a list of the links.

It is important to remember that in simple cases, it is much preferred to use native HTML controls and style them rather than using ARIA. That is don’t reinvent wheels, or checkboxes, if you don’t have to.

Fortunately, ARIA markup can be added to existing sites without changing the behavior for mainstream users. This greatly reduces the cost of modifying and testing the website or application.

How do I prevent a Gateway Timeout with FastCGI on Nginx

For those using nginx with unicorn and rails, most likely the timeout is in your unicorn.rb file

put a large timeout in unicorn.rb

timeout 500

if you're still facing issues, try having fail_timeout=0 in your upstream in nginx and see if this fixes your issue. This is for debugging purposes and might be dangerous in a production environment.

upstream foo_server {
        server 127.0.0.1:3000 fail_timeout=0;
}

get dataframe row count based on conditions

You are asking for the condition where all the conditions are true, so len of the frame is the answer, unless I misunderstand what you are asking

In [17]: df = DataFrame(randn(20,4),columns=list('ABCD'))

In [18]: df[(df['A']>0) & (df['B']>0) & (df['C']>0)]
Out[18]: 
           A         B         C         D
12  0.491683  0.137766  0.859753 -1.041487
13  0.376200  0.575667  1.534179  1.247358
14  0.428739  1.539973  1.057848 -1.254489

In [19]: df[(df['A']>0) & (df['B']>0) & (df['C']>0)].count()
Out[19]: 
A    3
B    3
C    3
D    3
dtype: int64

In [20]: len(df[(df['A']>0) & (df['B']>0) & (df['C']>0)])
Out[20]: 3

Is there a way to get the XPath in Google Chrome?

I tried almost all the available extensions and found the below to be one of the best.

ChroPath Extension link

Just like FirePath, this extension directly gives you the Xpath when you click on Inspect.

enter image description here

Java equivalent of unsigned long long?

Starting Java 8, there is support for unsigned long (unsigned 64 bits). The way you can use it is:

Long l1 = Long.parseUnsignedLong("17916881237904312345");

To print it, you can not simply print l1, but you have to first:

String l1Str = Long.toUnsignedString(l1)

Then

System.out.println(l1Str);

Exporting the values in List to excel

Exporting values List to Excel

  1. Install in nuget next reference
  2. Install-Package Syncfusion.XlsIO.Net.Core -Version 17.2.0.35
  3. Install-Package ClosedXML -Version 0.94.2
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ClosedXML;
using ClosedXML.Excel;
using Syncfusion.XlsIO;

namespace ExporteExcel
{
    class Program
    {
        public class Auto
        {
            public string Marca { get; set; }

            public string Modelo { get; set; }
            public int Ano { get; set; }

            public string Color { get; set; }
            public int Peronsas { get; set; }
            public int Cilindros { get; set; }
        }
        static void Main(string[] args)
        {
            //Lista Estatica
            List<Auto> Auto = new List<Program.Auto>()
            {
                new Auto{Marca = "Chevrolet", Modelo = "Sport", Ano = 2019, Color= "Azul", Cilindros=6, Peronsas= 4 },
                new Auto{Marca = "Chevrolet", Modelo = "Sport", Ano = 2018, Color= "Azul", Cilindros=6, Peronsas= 4 },
                new Auto{Marca = "Chevrolet", Modelo = "Sport", Ano = 2017, Color= "Azul", Cilindros=6, Peronsas= 4 }
            };
            //Inizializar Librerias
            var workbook = new XLWorkbook();
            workbook.AddWorksheet("sheetName");
            var ws = workbook.Worksheet("sheetName");
            //Recorrer el objecto
            int row = 1;
            foreach (var c in Auto)
            {
                //Escribrie en Excel en cada celda
                ws.Cell("A" + row.ToString()).Value = c.Marca;
                ws.Cell("B" + row.ToString()).Value = c.Modelo;
                ws.Cell("C" + row.ToString()).Value = c.Ano;
                ws.Cell("D" + row.ToString()).Value = c.Color;
                ws.Cell("E" + row.ToString()).Value = c.Cilindros;
                ws.Cell("F" + row.ToString()).Value = c.Peronsas;
                row++;

            }
            //Guardar Excel 
            //Ruta = Nombre_Proyecto\bin\Debug
            workbook.SaveAs("Coches.xlsx");
        }
    }
}

Issue with adding common code as git submodule: "already exists in the index"

Don't know if this is any useful, though I had the same problem when trying to commit my files from within IntelliJ 15. In the end, I opened SourceTree and in there I could simply commit the file. Problem solved. No need to issue any fancy git commands. Just mentioning it in case anyone has the same issue.

How can I delete all of my Git stashes at once?

this command enables you to look all stashed changes.

git stash list

Here is the following command use it to clear all of your stashed Changes

git stash clear

Now if you want to delete one of the stashed changes from stash area

git stash drop stash@{index}   // here index will be shown after getting stash list.

Note : git stash list enables you to get index from stash area of git.

How do I get the scroll position of a document?

You can try this for example, this code put the scrollbar at the bottom for all DIV tags

Remember: jQuery can accept a function instead the value as argument. "this" is the object treated by jQuery, the function returns the scrollHeight property of the current DIV "this" and do it for all DIV in the document.

$("div").scrollTop(function(){return this.scrollHeight})

pandas: best way to select all columns whose names start with X

Just perform a list comprehension to create your columns:

In [28]:

filter_col = [col for col in df if col.startswith('foo')]
filter_col
Out[28]:
['foo.aa', 'foo.bars', 'foo.fighters', 'foo.fox', 'foo.manchu']
In [29]:

df[filter_col]
Out[29]:
   foo.aa  foo.bars  foo.fighters  foo.fox foo.manchu
0     1.0         0             0        2         NA
1     2.1         0             1        4          0
2     NaN         0           NaN        1          0
3     4.7         0             0        0          0
4     5.6         0             0        0          0
5     6.8         1             0        5          0

Another method is to create a series from the columns and use the vectorised str method startswith:

In [33]:

df[df.columns[pd.Series(df.columns).str.startswith('foo')]]
Out[33]:
   foo.aa  foo.bars  foo.fighters  foo.fox foo.manchu
0     1.0         0             0        2         NA
1     2.1         0             1        4          0
2     NaN         0           NaN        1          0
3     4.7         0             0        0          0
4     5.6         0             0        0          0
5     6.8         1             0        5          0

In order to achieve what you want you need to add the following to filter the values that don't meet your ==1 criteria:

In [36]:

df[df[df.columns[pd.Series(df.columns).str.startswith('foo')]]==1]
Out[36]:
   bar.baz  foo.aa  foo.bars  foo.fighters  foo.fox foo.manchu nas.foo
0      NaN       1       NaN           NaN      NaN        NaN     NaN
1      NaN     NaN       NaN             1      NaN        NaN     NaN
2      NaN     NaN       NaN           NaN        1        NaN     NaN
3      NaN     NaN       NaN           NaN      NaN        NaN     NaN
4      NaN     NaN       NaN           NaN      NaN        NaN     NaN
5      NaN     NaN         1           NaN      NaN        NaN     NaN

EDIT

OK after seeing what you want the convoluted answer is this:

In [72]:

df.loc[df[df[df.columns[pd.Series(df.columns).str.startswith('foo')]] == 1].dropna(how='all', axis=0).index]
Out[72]:
   bar.baz  foo.aa  foo.bars  foo.fighters  foo.fox foo.manchu nas.foo
0      5.0     1.0         0             0        2         NA      NA
1      5.0     2.1         0             1        4          0       0
2      6.0     NaN         0           NaN        1          0       1
5      6.8     6.8         1             0        5          0       0

How to count number of unique values of a field in a tab-delimited text file?

# COLUMN is integer column number
# INPUT_FILE is input file name

cut -f ${COLUMN} < ${INPUT_FILE} | sort -u | wc -l

Examples of good gotos in C or C++

Here's my non-silly example, (from Stevens APITUE) for Unix system calls which may be interrupted by a signal.

restart:
    if (system_call() == -1) {
        if (errno == EINTR) goto restart;

        // handle real errors
    }

The alternative is a degenerate loop. This version reads like English "if the system call was interrupted by a signal, restart it".

Select records from today, this week, this month php mysql

You can do same thing using single query

SELECT sum(if(DATE(dDate)=DATE(CURRENT_TIMESTAMP),earning,null)) astodays,
       sum(if(YEARWEEK(dDate)=YEARWEEK(CURRENT_DATE),earning,null)) as weeks, 
       IF((MONTH(dDate) = MONTH(CURRENT_TIMESTAMP()) AND YEAR(dDate) = YEAR(CURRENT_TIMESTAMP())),sum(earning),0) AS months,
       IF(YEAR(dDate) = YEAR(CURRENT_TIMESTAMP()),sum(earning),0) AS years, 
       sum(fAdminFinalEarning) as total_earning FROM `earning`

Hope this works.

Styling an anchor tag to look like a submit button

I Suggest you to use both Input Submit / Button instead of anchor and put this line of code onClick="javascript:location.href = 'http://stackoverflow.com';" in that Input Submit / Button which you want to work as link.

Submit Example

<input type="submit" value="Submit" onClick="javascript:location.href = 'some_url';" />

Button Example

<button type="button" onClick="javascript:location.href = 'some_url';" />Submit</button>

How to create a TextArea in Android

<EditText
    android:id="@+id/comments_textbox"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="comments"
    android:inputType="textMultiLine"
    android:longClickable="false" />

use it to create multi line text box like textArea in Html

jQuery when element becomes visible

A catch-all jQuery custom event based on an extension of it's core methods like it was proposed by different people in this thread:

(function() {
    var ev = new $.Event('event.css.jquery'),
        css = $.fn.css,
        show = $.fn.show,
        hide = $.fn.hide;

    // extends css()
    $.fn.css = function() {
        css.apply(this, arguments);
        $(this).trigger(ev);
    };

    // extends show()
    $.fn.show = function() {
        show.apply(this, arguments);
        $(this).trigger(ev);
    };

    // extends hide()
    $.fn.hide = function() {
        hide.apply(this, arguments);
        $(this).trigger(ev);
    };
})();

An external library then, uses sth like $('selector').css('property', value).

As we don't want to alter the library's code but we DO want to extend it's behavior we do sth like:

$('#element').on('event.css.jquery', function(e) {
    // ...more code here...
});

Example: user clicks on a panel that is built by a library. The library shows/hides elements based on user interaction. We want to add a sensor that shows that sth has been hidden/shown because of that interaction and should be called after the library's function.

Another example: jsfiddle.

"Invalid JSON primitive" in Ajax processing

On the Server, to Serialize/Deserialize json to custom objects:

public static string Serialize<T>(T obj)
{
    DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
    MemoryStream ms = new MemoryStream();
    serializer.WriteObject(ms, obj);
    string retVal = Encoding.UTF8.GetString(ms.ToArray());
    return retVal;
}

public static T Deserialize<T>(string json)
{
    T obj = Activator.CreateInstance<T>();
    MemoryStream ms = new MemoryStream(Encoding.Unicode.GetBytes(json));
    DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
    obj = (T)serializer.ReadObject(ms);
    ms.Close();
    return obj;
}

Java check if boolean is null

null is a value assigned to a reference type. null is a reserved value, indicating that a reference does not resemble an instance of an object.

A boolean is not an instance of an Object. It is a primitive type, like int and float. In the same way that: int x has a value of 0, boolean x has a value of false.

Using Excel OleDb to get sheet names IN SHEET ORDER

Try this. Here is the code to get the sheet names in order.

private Dictionary<int, string> GetExcelSheetNames(string fileName)
{
    Excel.Application _excel = null;
    Excel.Workbook _workBook = null;
    Dictionary<int, string> excelSheets = new Dictionary<int, string>();
    try
    {
        object missing = Type.Missing;
        object readOnly = true;
        Excel.XlFileFormat.xlWorkbookNormal
        _excel = new Excel.ApplicationClass();
        _excel.Visible = false;
        _workBook = _excel.Workbooks.Open(fileName, 0, readOnly, 5, missing,
            missing, true, Excel.XlPlatform.xlWindows, "\\t", false, false, 0, true, true, missing);
        if (_workBook != null)
        {
            int index = 0;
            foreach (Excel.Worksheet sheet in _workBook.Sheets)
            {
                // Can get sheet names in order they are in workbook
                excelSheets.Add(++index, sheet.Name);
            }
        }
    }
    catch (Exception e)
    {
        return null;
    }
    finally
    {
        if (_excel != null)
        {

            if (_workBook != null)
                _workBook.Close(false, Type.Missing, Type.Missing);
            _excel.Application.Quit();
        }
        _excel = null;
        _workBook = null;
    }
    return excelSheets;
}

Eclipse C++: Symbol 'std' could not be resolved

Try out this step: https://www.eclipse.org/forums/index.php/t/636348/

Go to

Project -> Properties -> C/C++ General -> Preprocessor Include Paths, Macros, etc. -> Providers

  • Activate CDT GCC Built-in Compiler Settings
  • Deactivate Use global provider shared between projects
  • Add the command line argument -std=c++11.

example

jQuery: If this HREF contains

Try this:

$("a").each(function() {
    if ($('[href$="?"]', this).length()) {
        alert("Contains questionmark");
    }
});

Sort a list of lists with a custom compare function

>>> l = [list(range(i, i+4)) for i in range(10,1,-1)]
>>> l
[[10, 11, 12, 13], [9, 10, 11, 12], [8, 9, 10, 11], [7, 8, 9, 10], [6, 7, 8, 9], [5, 6, 7, 8], [4, 5, 6, 7], [3, 4, 5, 6], [2, 3, 4, 5]]
>>> sorted(l, key=sum)
[[2, 3, 4, 5], [3, 4, 5, 6], [4, 5, 6, 7], [5, 6, 7, 8], [6, 7, 8, 9], [7, 8, 9, 10], [8, 9, 10, 11], [9, 10, 11, 12], [10, 11, 12, 13]]

The above works. Are you doing something different?

Notice that your key function is just sum; there's no need to write it explicitly.

Get host domain from URL?

You should construct your string as URI object and Authority property returns what you need.

SQL: how to select a single id ("row") that meets multiple criteria from a single column

like the answer above but I have a duplicate record so I have to create a subquery with distinct

Select user_id
(
   select distinct userid
   from yourtable
   where user_id = @userid

) t1
where 
ancestry in ('England', 'France', 'Germany')
group by user_id
having count(user_id) = 3

this is what I used because I have multiple record(download logs) and this checks that all the required files have been downloaded

Rails 3: I want to list all paths defined in my rails application

rake routes | grep <specific resource name>

displays resource specific routes, if it is a pretty long list of routes.

No module named serial

Download this file :- (https://pypi.python.org/packages/1f/3b/ee6f354bcb1e28a7cd735be98f39ecf80554948284b41e9f7965951befa6/pyserial-3.2.1.tar.gz#md5=7142a421c8b35d2dac6c47c254db023d):

cd /opt
sudo tar -xvf ~/Downloads/pyserial-3.2.1.tar.gz -C .
cd /opt/pyserial-3.2.1 
sudo python setup.py install 

Turning off eslint rule for a specific line

The general end of line comment, // eslint-disable-line, does not need anything after it: no need to look up a code to specify what you wish ES Lint to ignore.

If you need to have any syntax ignored for any reason other than a quick debugging, you have problems: why not update your delint config?

I enjoy // eslint-disable-line to allow me to insert console for a quick inspection of a service, without my development environment holding me back because of the breach of protocol. (I generally ban console, and use a logging class - which sometimes builds upon console.)

How to convert an xml string to a dictionary?

The following XML-to-Python-dict snippet parses entities as well as attributes following this XML-to-JSON "specification". It is the most general solution handling all cases of XML.

from collections import defaultdict

def etree_to_dict(t):
    d = {t.tag: {} if t.attrib else None}
    children = list(t)
    if children:
        dd = defaultdict(list)
        for dc in map(etree_to_dict, children):
            for k, v in dc.items():
                dd[k].append(v)
        d = {t.tag: {k:v[0] if len(v) == 1 else v for k, v in dd.items()}}
    if t.attrib:
        d[t.tag].update(('@' + k, v) for k, v in t.attrib.items())
    if t.text:
        text = t.text.strip()
        if children or t.attrib:
            if text:
              d[t.tag]['#text'] = text
        else:
            d[t.tag] = text
    return d

It is used:

from xml.etree import cElementTree as ET
e = ET.XML('''
<root>
  <e />
  <e>text</e>
  <e name="value" />
  <e name="value">text</e>
  <e> <a>text</a> <b>text</b> </e>
  <e> <a>text</a> <a>text</a> </e>
  <e> text <a>text</a> </e>
</root>
''')

from pprint import pprint
pprint(etree_to_dict(e))

The output of this example (as per above-linked "specification") should be:

{'root': {'e': [None,
                'text',
                {'@name': 'value'},
                {'#text': 'text', '@name': 'value'},
                {'a': 'text', 'b': 'text'},
                {'a': ['text', 'text']},
                {'#text': 'text', 'a': 'text'}]}}

Not necessarily pretty, but it is unambiguous, and simpler XML inputs result in simpler JSON. :)


Update

If you want to do the reverse, emit an XML string from a JSON/dict, you can use:

try:
  basestring
except NameError:  # python3
  basestring = str

def dict_to_etree(d):
    def _to_etree(d, root):
        if not d:
            pass
        elif isinstance(d, basestring):
            root.text = d
        elif isinstance(d, dict):
            for k,v in d.items():
                assert isinstance(k, basestring)
                if k.startswith('#'):
                    assert k == '#text' and isinstance(v, basestring)
                    root.text = v
                elif k.startswith('@'):
                    assert isinstance(v, basestring)
                    root.set(k[1:], v)
                elif isinstance(v, list):
                    for e in v:
                        _to_etree(e, ET.SubElement(root, k))
                else:
                    _to_etree(v, ET.SubElement(root, k))
        else:
            raise TypeError('invalid type: ' + str(type(d)))
    assert isinstance(d, dict) and len(d) == 1
    tag, body = next(iter(d.items()))
    node = ET.Element(tag)
    _to_etree(body, node)
    return ET.tostring(node)

pprint(dict_to_etree(d))

Converting Numpy Array to OpenCV Array

The simplest solution would be to use Pillow lib:

from PIL import Image

image = Image.fromarray(<your_numpy_array>.astype(np.uint8))

And you can use it as an image.

Print empty line?

You can just do

print()

to get an empty line.

Efficiently convert rows to columns in sql server

There are several ways that you can transform data from multiple rows into columns.

Using PIVOT

In SQL Server you can use the PIVOT function to transform the data from rows to columns:

select Firstname, Amount, PostalCode, LastName, AccountNumber
from
(
  select value, columnname
  from yourtable
) d
pivot
(
  max(value)
  for columnname in (Firstname, Amount, PostalCode, LastName, AccountNumber)
) piv;

See Demo.

Pivot with unknown number of columnnames

If you have an unknown number of columnnames that you want to transpose, then you can use dynamic SQL:

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT ',' + QUOTENAME(ColumnName) 
                    from yourtable
                    group by ColumnName, id
                    order by id
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = N'SELECT ' + @cols + N' from 
             (
                select value, ColumnName
                from yourtable
            ) x
            pivot 
            (
                max(value)
                for ColumnName in (' + @cols + N')
            ) p '

exec sp_executesql @query;

See Demo.

Using an aggregate function

If you do not want to use the PIVOT function, then you can use an aggregate function with a CASE expression:

select
  max(case when columnname = 'FirstName' then value end) Firstname,
  max(case when columnname = 'Amount' then value end) Amount,
  max(case when columnname = 'PostalCode' then value end) PostalCode,
  max(case when columnname = 'LastName' then value end) LastName,
  max(case when columnname = 'AccountNumber' then value end) AccountNumber
from yourtable

See Demo.

Using multiple joins

This could also be completed using multiple joins, but you will need some column to associate each of the rows which you do not have in your sample data. But the basic syntax would be:

select fn.value as FirstName,
  a.value as Amount,
  pc.value as PostalCode,
  ln.value as LastName,
  an.value as AccountNumber
from yourtable fn
left join yourtable a
  on fn.somecol = a.somecol
  and a.columnname = 'Amount'
left join yourtable pc
  on fn.somecol = pc.somecol
  and pc.columnname = 'PostalCode'
left join yourtable ln
  on fn.somecol = ln.somecol
  and ln.columnname = 'LastName'
left join yourtable an
  on fn.somecol = an.somecol
  and an.columnname = 'AccountNumber'
where fn.columnname = 'Firstname'

error MSB6006: "cmd.exe" exited with code 1

Simple and better solution : %WINDIR%\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe MyProject.sln I make a bat file like this %WINDIR%\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe D:\GESTION-SOMECOPA\GestionCommercial\GestionCommercial.sln pause

Then I can see all errors and correct them. Because when you change the folder name (without spaces as seen above) you will have another problems. Visual Studio 2015 works fine after this.

JOIN queries vs multiple queries

In my experience I have found it's usually faster to run several queries, especially when retrieving large data sets.

When interacting with the database from another application, such as PHP, there is the argument of one trip to the server over many.

There are other ways to limit the number of trips made to the server and still run multiple queries that are often not only faster but also make the application easier to read - for example mysqli_multi_query.

I'm no novice when it comes to SQL, I think there is a tendency for developers, especially juniors to spend a lot of time trying to write very clever joins because they look smart, whereas there are actually smart ways to extract data that look simple.

The last paragraph was a personal opinion, but I hope this helps. I do agree with the others though who say you should benchmark. Neither approach is a silver bullet.

How do I open multiple instances of Visual Studio Code?

To open a new instance with your project loaded from terminal, just type code <directory-path>

FirebaseInstanceIdService is deprecated

Just Add This On build.gradle. implementation 'com.google.firebase:firebase-messaging:20.2.3'

Override body style for content in an iframe

This code uses vanilla JavaScript. It creates a new <style> element. It sets the text content of that element to be a string containing the new CSS. And it appends that element directly to the iframe document's head.

Keep in mind, however, that accessing elements of a document loaded from another origin is not permitted (for security reasons) -- contentDocument of the iframe element will evaluate to null when attempted from the browsing context of the page embedding the frame.

var iframe = document.getElementById('the-iframe');
var style = document.createElement('style');
style.textContent =
  'body {' +
  '  background-color: some-color;' +
  '  background-image: some-image;' +
  '}' 
;
iframe.contentDocument.head.appendChild(style);

From Now() to Current_timestamp in Postgresql

Here is an example ...

select * from tablename where to_char(added_time, 'YYYY-MM-DD')  = to_char( now(), 'YYYY-MM-DD' )

added_time is a column name which I converted to char for match

C# event with custom arguments

EventHandler receives EventArgs as a parameter. To resolve your problem, you can build your own MyEventArgs.

 public enum MyEvents
 { 
    Event1 
 }

 public class MyEventArgs : EventArgs
 {
    public MyEvents MyEvent { get; set; }
 }

 public static event EventHandler<MyEventArgs> EventTriggered; 

 public static void Trigger(MyEvents ev) 
 { 
     if (EventTriggered != null) 
     {
         EventTriggered(null, new MyEventArgs { MyEvent = ev });
     } 
 } 

In C#, what is the difference between public, private, protected, and having no access modifier?

enter image description here

using System;

namespace ClassLibrary1
{
    public class SameAssemblyBaseClass
    {
        public string publicVariable = "public";
        protected string protectedVariable = "protected";
        protected internal string protected_InternalVariable = "protected internal";
        internal string internalVariable = "internal";
        private string privateVariable = "private";
        public void test()
        {
            // OK
            Console.WriteLine(privateVariable);

            // OK
            Console.WriteLine(publicVariable);

            // OK
            Console.WriteLine(protectedVariable);

            // OK
            Console.WriteLine(internalVariable);

            // OK
            Console.WriteLine(protected_InternalVariable);
        }
    }

    public class SameAssemblyDerivedClass : SameAssemblyBaseClass
    {
        public void test()
        {
            SameAssemblyDerivedClass p = new SameAssemblyDerivedClass();

            // NOT OK
            // Console.WriteLine(privateVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);
        }
    }

    public class SameAssemblyDifferentClass
    {
        public SameAssemblyDifferentClass()
        {
            SameAssemblyBaseClass p = new SameAssemblyBaseClass();

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.internalVariable);

            // NOT OK
            // Console.WriteLine(privateVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protectedVariable' is inaccessible due to its protection level
            //Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);
        }
    }
}

 using System;
        using ClassLibrary1;
        namespace ConsoleApplication4

{
    class DifferentAssemblyClass
    {
        public DifferentAssemblyClass()
        {
            SameAssemblyBaseClass p = new SameAssemblyBaseClass();

            // NOT OK
            // Console.WriteLine(p.privateVariable);

            // NOT OK
            // Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protectedVariable' is inaccessible due to its protection level
            // Console.WriteLine(p.protectedVariable);

            // Error : 'ClassLibrary1.SameAssemblyBaseClass.protected_InternalVariable' is inaccessible due to its protection level
            // Console.WriteLine(p.protected_InternalVariable);
        }
    }

    class DifferentAssemblyDerivedClass : SameAssemblyBaseClass
    {
        static void Main(string[] args)
        {
            DifferentAssemblyDerivedClass p = new DifferentAssemblyDerivedClass();

            // NOT OK
            // Console.WriteLine(p.privateVariable);

            // NOT OK
            //Console.WriteLine(p.internalVariable);

            // OK
            Console.WriteLine(p.publicVariable);

            // OK
            Console.WriteLine(p.protectedVariable);

            // OK
            Console.WriteLine(p.protected_InternalVariable);

            SameAssemblyDerivedClass dd = new SameAssemblyDerivedClass();
            dd.test();
        }
    }
}

Namespace not recognized (even though it is there)

In my case removing/adding that assembly worked.

How to remove hashbang from url?

You'd actually just want to set mode to 'history'.

const router = new VueRouter({
  mode: 'history'
})

Make sure your server is configured to handle these links, though. https://router.vuejs.org/guide/essentials/history-mode.html

How to pass a JSON array as a parameter in URL

let qs = event.queryStringParameters;
const query = Object.keys(qs).map(key => key + '=' + qs[key]).join('&');

nginx error:"location" directive is not allowed here in /etc/nginx/nginx.conf:76

The server directive has to be in the http directive. It should not be outside of it.

Incase if you need detailed information, refer this.

How can I pass variable to ansible playbook in the command line?

For some reason none of the above Answers worked for me. As I need to pass several extra vars to my playbook in Ansbile 2.2.0, this is how I got it working (note the -e option before each var):

ansible-playbook site.yaml -i hostinv -e firstvar=false -e second_var=value2

How can I require at least one checkbox be checked before a form can be submitted?

For php, when you use checkboxes for multiple values, the name always ends with []. We can use this to make the solution a bit more generic. And, since I put my error message in a data-message-value-missing attribute, I use:

$form.on('change', 'input[type=checkbox][name$="[]"]', e => {
    const $inputs = $('input[type=checkbox][name="' + e.target.name + '"]');
    const $targetInp = $inputs.filter('[data-message-value-missing]');
    if($inputs.filter(':checked').length) {
        $targetInp.removeAttr('required');
        $form.find('label.error').html('');
    } else {
        $targetInp.attr('required', 'required');
    }
});

To make this work, set the data-message-value-missing and the required on only one (the last) input:

<ul>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 1"><label>Box 1</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 2"><label>Box 2</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 3"><label>Box 3</label></li>
   <li><input name="BoxSelect[]" type="checkbox" value="Box 4" required data-message-value-missing="Select at least one"><label>Box 4</label></li>
</ul>

I excluded the code to handle the checkValidity(), etc. Seems beyond the scope of this question...

Bootstrap Modal immediately disappearing

In my case, I had only a single bootstrap.js, jquery.js file included but still getting such type of error, and my code for button was something like this:

<script type="text/javascript">
$(document).ready(function(){
   $("#bttn_<?php echo $rnt['id'];?>").click(function(){
      $("#myModal_<?php echo $rnt['id'];?>").modal('show');
   });
});
</script>

I simple added e.preventDefault(); to it and it worked like charm.

So, my new code was like below:

<script type="text/javascript">
$(document).ready(function(){
  e.preventDefault();
  $("#bttn_<?php echo $rnt['id'];?>").click(function(){
     $("#myModal_<?php echo $rnt['id'];?>").modal('show');
  });
});
</script>

What is the difference between field, variable, attribute, and property in Java POJOs?

From here: http://docs.oracle.com/javase/tutorial/information/glossary.html


  • field

    • A data member of a class. Unless specified otherwise, a field is not static.

  • property

    • Characteristics of an object that users can set, such as the color of a window.

  • attribute

    • Not listed in the above glossary

  • variable

    • An item of data named by an identifier. Each variable has a type, such as int or Object, and a scope. See also class variable, instance variable, local variable.

How to format an inline code in Confluence?

In Confluence 5.4.2 you can add surround your inline code with <code></code> tags in the source editor thusly:

Confluence will show <code>this inline code</code> in a fixed font. 

This can be useful where there are many fragments to modify since the double-brace feature only works when adding text interactively in the Confluence editor.

Multiple models in a view

Use a view model that contains multiple view models:

   namespace MyProject.Web.ViewModels
   {
      public class UserViewModel
      {
          public UserDto User { get; set; }
          public ProductDto Product { get; set; }
          public AddressDto Address { get; set; }
      }
   }

In your view:

  @model MyProject.Web.ViewModels.UserViewModel

  @Html.LabelFor(model => model.User.UserName)
  @Html.LabelFor(model => model.Product.ProductName)
  @Html.LabelFor(model => model.Address.StreetName)

Can't connect to local MySQL server through socket '/var/mysql/mysql.sock' (38)

I got this error when I set cron job for my file. I changed the permissions of file to 777 but it still not worked for me. Finally I got the solution. May be it will be helpful for others.

Try with this command:

mysql -h 127.0.0.1 -P 3306 -u root -p

Remember that -h means host, -P means port and -p means password.

C++ pointer to objects

First I need to say that your code,

MyClass *myclass;
myclass->DoSomething();

will cause an undefined behavior. Because the pointer "myclass" isn't pointing to any "MyClass" type objects.

Here I have three suggestions for you:-

option 1:- You can simply declare and use a MyClass type object on the stack as below.

MyClass myclass; //allocates memory for the object "myclass", on the stack.
myclass.DoSomething();

option 2:- By using the new operator.

MyClass *myclass = new MyClass();

Three things will hapen here.

i) Allocates memory for the "MyClass" type object on the heap.

ii) Allocates memory for the "MyClass" type pointer "myclass" on the stack.

iii) pointer "myclass" points to the memory address of "MyClass" type object on the heap

Now you can use the pointer to access member functions of the object after dereferencing the pointer by "->"

myclass->DoSomething();

But you should free the memory allocated to "MyClass" type object on the heap, before returning from the scope unless you want it to exists. Otherwise it will cause a memory leak!

delete myclass; // free the memory pointed by the pointer "myclass"

option 3:- you can also do as below.

MyClass myclass; // allocates memory for the "MyClass" type object on the stack.
MyClass *myclassPtr; // allocates memory for the "MyClass" type pointer on the stack.
myclassPtr = &myclass; // "myclassPtr" pointer points to the momory address of myclass object.

Now, pointer and object both are on the stack. Now you can't return this pointer to the outside of the current scope because both allocated memory of the pointer and the object will be freed while stepping outside the scope.

So as a summary, option 1 and 3 will allocate an object on the stack while only the option 2 will do it on the heap.

phpmailer - The following SMTP Error: Data not accepted

If you are using the Office 365 SMTP gateway then "SMTP Error: data not accepted." is the response you will get if the mailbox is full (even if you are just sending from it).

Try deleting some messages out of the mailbox.

Autoresize View When SubViews are Added

Yes, it is because you are using auto layout. Setting the view frame and resizing mask will not work.

You should read Working with Auto Layout Programmatically and Visual Format Language.

You will need to get the current constraints, add the text field, adjust the contraints for the text field, then add the correct constraints on the text field.

Manually install Gradle and use it in Android Studio

Assuming this is a windows system and we are using gradle-2.1-all [Applicable to any gradle version, just change the version as we need]

All the gradles can be found in http://services.gradle.org/distributions/


Check the <Your Project>\gradle\wrapper\gradle-wrapper.properties Make sure the distributionUrl is

distributionUrl=http\://services.gradle.org/distributions/gradle-2.1-all.zip

This is enough as it will automatically download the gradle.

After doing the above stuff, if you have downloaded the zip, paste the gradle-2.1-all.zip in

C:\Users\<username>\.gradle\wrapper\dists\gradle-2.1-all\<some_hash_key>\

It will save the extra downloading time.

In php, is 0 treated as empty?

I was recently caught with my pants down on this one as well. The issue we often deal with is unset variables - say a form element that may or may not have been there, but for many elements, 0 (or the string '0' which would come through the post more accurately, but still would be evaluated as "falsey") is a legitimate value say on a dropdown list.

using empty() first and then strlen() is your best best if you need this as well, as:

if(!empty($var) && strlen($var)){
    echo '"$var" is present and has a non-falsey value!';
}

Can I run multiple programs in a Docker container?

They can be in separate containers, and indeed, if the application was also intended to run in a larger environment, they probably would be.

A multi-container system would require some more orchestration to be able to bring up all the required dependencies, though in Docker v0.6.5+, there is a new facility to help with that built into Docker itself - Linking. With a multi-machine solution, its still something that has to be arranged from outside the Docker environment however.

With two different containers, the two parts still communicate over TCP/IP, but unless the ports have been locked down specifically (not recommended, as you'd be unable to run more than one copy), you would have to pass the new port that the database has been exposed as to the application, so that it could communicate with Mongo. This is again, something that Linking can help with.

For a simpler, small installation, where all the dependencies are going in the same container, having both the database and Python runtime started by the program that is initially called as the ENTRYPOINT is also possible. This can be as simple as a shell script, or some other process controller - Supervisord is quite popular, and a number of examples exist in the public Dockerfiles.

Undoing a git rebase

Charles's answer works, but you may want to do this:

git rebase --abort

to clean up after the reset.

Otherwise, you may get the message “Interactive rebase already started”.

Creating a very simple linked list

Based on what @jjnguy said, and fixing the bug in his PrintAllNodes(), here's the full Console App example:

public class Node
{
    public Node next;
    public Object data;
}

public class LinkedList
{
    private Node head;

    public void printAllNodes()
    {
        Node current = head;
        while (current != null)
        {
            Console.WriteLine(current.data);
            current = current.next;
        }
    }

    public void AddFirst(Object data)
    {
        Node toAdd = new Node();

        toAdd.data = data;
        toAdd.next = head;

        head = toAdd;
    }

    public void AddLast(Object data)
    {
        if (head == null)
        {
            head = new Node();

            head.data = data;
            head.next = null;
        }
        else
        {
            Node toAdd = new Node();
            toAdd.data = data;

            Node current = head;
            while (current.next != null)
            {
                current = current.next;
            }

            current.next = toAdd;
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Add First:");
        LinkedList myList1 = new LinkedList();

        myList1.AddFirst("Hello");
        myList1.AddFirst("Magical");
        myList1.AddFirst("World");
        myList1.printAllNodes();

        Console.WriteLine();

        Console.WriteLine("Add Last:");
        LinkedList myList2 = new LinkedList();

        myList2.AddLast("Hello");
        myList2.AddLast("Magical");
        myList2.AddLast("World");
        myList2.printAllNodes();

        Console.ReadLine();
    }
}

Why do people say that Ruby is slow?

Why is Ruby considered slow?

Because if you run typical benchmarks between Ruby and other languages, Ruby loses.

I do not find Ruby to be slow but then again, I'm just using it to make simple CRUD apps and company blogs. What sort of projects would I need to be doing before I find Ruby becoming slow? Or is this slowness just something that affects all programming languages?

Ruby probably wouldn't serve you well in writing a real-time digital signal processing application, or any kind of real-time control system. Ruby (with today's VMs) would probably choke on a resource-constrained computer such as smartphones.

Remember that a lot of the processing on your web applications is actually done by software developed in C. e.g. Apache, Thin, Nginx, SQLite, MySQL, PostgreSQL, many parsing libraries, RMagick, TCP/IP, etc are C programs used by Ruby. Ruby provides the glue and the business logic.

What are your options as a Ruby programmer if you want to deal with this "slowness"?

Switch to a faster language. But that carries a cost. It is a cost that may be worth it. But for most web applications, language choice is not a relevant factor because there is just not enough traffic justify using a faster language that costs much more to develop for.

Which version of Ruby would best suit an application like Stack Overflow where speed is critical and traffic is intense?

Other folks have answered this - JRuby, IronRuby, REE will make the Ruby part of your application run faster on platforms that can afford the VMs. And since it is often not Ruby that causes slowness, but your computer system architecture and application architecture, you can do stuff like database replication, multiple application servers, loadbalancing with reverse proxies, HTTP caching, memcache, Ajax, client-side caching, etc. None of this stuff is Ruby.

Finally, I can't find much news on Ruby 2.0 - I take it we're a good few years away from that then?

Most folks are waiting for Ruby 1.9.1. I myself am waiting for Rails 3.1 on Ruby 1.9.1 on JRuby.

Finally, please remember that a lot of developers choose Ruby because it makes programming a more joyful experience compared to other languages, and because Ruby with Rails enables skilled web developers to develop applications very quickly.

Watermark / hint text / placeholder TextBox

you can use GetFocus() and LostFocus() events to do this

here is the example:

    private void txtData1_GetFocus(object sender, RoutedEventArgs e)
    {
        if (txtData1.Text == "TextBox1abc")
        {
            txtData1.Text = string.Empty;
        }
    }

    private void txtData1_LostFocus(object sender, RoutedEventArgs e)
    {
        if (txtData1.Text == string.Empty)
        {
            txtData1.Text = "TextBox1abc";
        }
    }

In Objective-C, how do I test the object type?

When you want to differ between a superClass and the inheritedClass you can use:

if([myTestClass class] == [myInheritedClass class]){
   NSLog(@"I'm the inheritedClass);
} 
if([myTestClass class] == [mySuperClass class]){
   NSLog(@"I'm the superClass);
} 

Using - (BOOL)isKindOfClass:(Class)aClass in this case would result in TRUE both times because the inheritedClass is also a kind of the superClass.

HTTP error 403 in Python 3 Web Scraping

You can try in two ways. The detail is in this link.

1) Via pip

pip install --upgrade certifi

2) If it doesn't work, try to run a Cerificates.command that comes bundled with Python 3.* for Mac:(Go to your python installation location and double click the file)

open /Applications/Python\ 3.*/Install\ Certificates.command

What is the difference between find(), findOrFail(), first(), firstOrFail(), get(), list(), toArray()

  1. find($id) takes an id and returns a single model. If no matching model exist, it returns null.

  2. findOrFail($id) takes an id and returns a single model. If no matching model exist, it throws an error1.

  3. first() returns the first record found in the database. If no matching model exist, it returns null.

  4. firstOrFail() returns the first record found in the database. If no matching model exist, it throws an error1.

  5. get() returns a collection of models matching the query.

  6. pluck($column) returns a collection of just the values in the given column. In previous versions of Laravel this method was called lists.

  7. toArray() converts the model/collection into a simple PHP array.


Note: a collection is a beefed up array. It functions similarly to an array, but has a lot of added functionality, as you can see in the docs.

Unfortunately, PHP doesn't let you use a collection object everywhere you can use an array. For example, using a collection in a foreach loop is ok, put passing it to array_map is not. Similarly, if you type-hint an argument as array, PHP won't let you pass it a collection. Starting in PHP 7.1, there is the iterable typehint, which can be used to accept both arrays and collections.

If you ever want to get a plain array from a collection, call its all() method.


1 The error thrown by the findOrFail and firstOrFail methods is a ModelNotFoundException. If you don't catch this exception yourself, Laravel will respond with a 404, which is what you want most of the time.

How to write a switch statement in Ruby

You can use regular expressions, such as finding a type of string:

case foo
when /^(true|false)$/
   puts "Given string is boolean"
when /^[0-9]+$/ 
   puts "Given string is integer"
when /^[0-9\.]+$/
   puts "Given string is float"
else
   puts "Given string is probably string"
end

Ruby's case will use the equality operand === for this (thanks @JimDeville). Additional information is available at "Ruby Operators". This also can be done using @mmdemirbas example (without parameter), only this approach is cleaner for these types of cases.

Importing a CSV file into a sqlite3 database table using Python

I've found that it can be necessary to break up the transfer of data from the csv to the database in chunks as to not run out of memory. This can be done like this:

import csv
import sqlite3
from operator import itemgetter

# Establish connection
conn = sqlite3.connect("mydb.db")

# Create the table 
conn.execute(
    """
    CREATE TABLE persons(
        person_id INTEGER,
        last_name TEXT, 
        first_name TEXT, 
        address TEXT
    )
    """
)

# These are the columns from the csv that we want
cols = ["person_id", "last_name", "first_name", "address"]

# If the csv file is huge, we instead add the data in chunks
chunksize = 10000

# Parse csv file and populate db in chunks
with conn, open("persons.csv") as f:
    reader = csv.DictReader(f)

    chunk = []
    for i, row in reader: 

        if i % chunksize == 0 and i > 0:
            conn.executemany(
                """
                INSERT INTO persons
                    VALUES(?, ?, ?, ?)
                """, chunk
            )
            chunk = []

        items = itemgetter(*cols)(row)
        chunk.append(items)

Ajax - 500 Internal Server Error

This may be an incorrect parameter to your SOAP call; look at the format of the parameter(s) in the 'data:' json section - this is the payload you are passing over - parameter and data wrapped in JSON format.

Google Chrome's debugging toolbar has some good tools to verify parameters and look at error messages - for example, start with the Console tab and click on the URL which errors or click on the network tab. You will want to view the message's headers, response etc...

How to get an object's methods?

Get the Method Names:

var getMethodNames = function (obj) {
    return (Object.getOwnPropertyNames(obj).filter(function (key) {
        return obj[key] && (typeof obj[key] === "function");
    }));
};

Or, Get the Methods:

var getMethods     = function (obj) {
    return (Object.getOwnPropertyNames(obj).filter(function (key) {
        return obj[key] && (typeof obj[key] === "function");
    })).map(function (key) {
        return obj[key];
    });
};

Controller 'ngModel', required by directive '...', can't be found

You can also remove the line

  require: 'ngModel',

if you don't need ngModel in this directive. Removing ngModel will allow you to make a directive without thatngModel error.

How do you set autocommit in an SQL Server session?

I wanted a more permanent and quicker way. Because I tend to forget to add extra lines before writing my actual Update/Insert queries.

I did it by checking SET IMPLICIT_TRANSACTIONS check-box from Options. To navigate to Options Select Tools>Options>Query Execution>SQL Server>ANSI in your Microsoft SQL Server Management Studio.

Just make sure to execute commit or rollback after you are done executing your queries. Otherwise, the table you would have run the query will be locked for others.

How can I add an item to a IEnumerable<T> collection?

To add second message you need to -

IEnumerable<T> items = new T[]{new T("msg")};
items = items.Concat(new[] {new T("msg2")})