SyntaxFix

Programs & Examples On #Html parsing

HTML parsing is the process of consuming a serialization of an HTML document and producing a representation that you can work with programmatically — e.g., in order to extract data from it. The HTML specification defines a standard algorithm for parsing HTML, which is implemented in all major browsers.

Options for HTML scraping?

I've had some success with HtmlUnit, in Java. It's a simple framework for writing unit tests on web UI's, but equally useful for HTML scraping.

HTML Text with tags to formatted text in an Excel cell

Nice! Very slick.

I was disappointed that Excel doesn't let us paste to a merged cell and also pastes results containing a break into successive rows below the "target" cell though, as that meant it simply doesn't work for me. I tried a few tweaks (unmerge/remerge, etc.) but then Excel dropped anything below a break, so that was a dead end.

Ultimately, I came up with a routine that'll handle simple tags and not use the "native" Unicode converter that is causing the issue with merged fields. Hope others find this useful:

Public Sub AddHTMLFormattedText(rngA As Range, strHTML As String, Optional blnShowBadHTMLWarning As Boolean = False)
    ' Adds converts text formatted with basic HTML tags to formatted text in an Excel cell
    ' NOTE: Font Sizes not handled perfectly per HTML standard, but I find this method more useful!

    Dim strActualText As String, intSrcPos As Integer, intDestPos As Integer, intDestSrcEquiv() As Integer
    Dim varyTags As Variant, varTag As Variant, varEndTag As Variant, blnTagMatch As Boolean
    Dim intCtr As Integer
    Dim intStartPos As Integer, intEndPos As Integer, intActualStartPos As Integer, intActualEndPos As Integer
    Dim intFontSizeStartPos As Integer, intFontSizeEndPos As Integer, intFontSize As Integer

    varyTags = Array("<b>", "</b>", "<i>", "</i>", "<u>", "</u>", "<sub>", "</sub>", "<sup>", "</sup>")

    ' Remove unhandled/unneeded tags, convert <br> and <p> tags to line feeds
    strHTML = Trim(strHTML)
    strHTML = Replace(strHTML, "<html>", "")
    strHTML = Replace(strHTML, "</html>", "")
    strHTML = Replace(strHTML, "<p>", "")
    While LCase(Right$(strHTML, 4)) = "</p>" Or LCase(Right$(strHTML, 4)) = "<br>"
        strHTML = Left$(strHTML, Len(strHTML) - 4)
        strHTML = Trim(strHTML)
    Wend
    strHTML = Replace(strHTML, "<br>", vbLf)
    strHTML = Replace(strHTML, "</p>", vbLf)

    strHTML = Trim(strHTML)

    ReDim intDestSrcEquiv(1 To Len(strHTML))
    strActualText = ""
    intSrcPos = 1
    intDestPos = 1
    Do While intSrcPos <= Len(strHTML)
        blnTagMatch = False
        For Each varTag In varyTags
            If LCase(Mid$(strHTML, intSrcPos, Len(varTag))) = varTag Then
                blnTagMatch = True
                intSrcPos = intSrcPos + Len(varTag)
                If intSrcPos > Len(strHTML) Then Exit Do
                Exit For
            End If
        Next
        If blnTagMatch = False Then
            varTag = "<font size"
            If LCase(Mid$(strHTML, intSrcPos, Len(varTag))) = varTag Then
                blnTagMatch = True
                intEndPos = InStr(intSrcPos, strHTML, ">")
                intSrcPos = intEndPos + 1
                If intSrcPos > Len(strHTML) Then Exit Do
            Else
                varTag = "</font>"
                If LCase(Mid$(strHTML, intSrcPos, Len(varTag))) = varTag Then
                    blnTagMatch = True
                    intSrcPos = intSrcPos + Len(varTag)
                    If intSrcPos > Len(strHTML) Then Exit Do
                End If
            End If
        End If
        If blnTagMatch = False Then
            strActualText = strActualText & Mid$(strHTML, intSrcPos, 1)
            intDestSrcEquiv(intSrcPos) = intDestPos
            intDestPos = intDestPos + 1
            intSrcPos = intSrcPos + 1
        End If
    Loop

    ' Clear any bold/underline/italic/superscript/subscript formatting from cell
    rngA.Font.Bold = False
    rngA.Font.Underline = False
    rngA.Font.Italic = False
    rngA.Font.Subscript = False
    rngA.Font.Superscript = False

    rngA.Value = strActualText

    ' Now start applying Formats!"
    ' Start with Font Size first
    intSrcPos = 1
    intDestPos = 1
    Do While intSrcPos <= Len(strHTML)
        varTag = "<font size"
        If LCase(Mid$(strHTML, intSrcPos, Len(varTag))) = varTag Then
            intFontSizeStartPos = InStr(intSrcPos, strHTML, """") + 1
            intFontSizeEndPos = InStr(intFontSizeStartPos, strHTML, """") - 1
            If intFontSizeEndPos - intFontSizeStartPos <= 3 And intFontSizeEndPos - intFontSizeStartPos > 0 Then
                Debug.Print Mid$(strHTML, intFontSizeStartPos, intFontSizeEndPos - intFontSizeStartPos + 1)
                If Mid$(strHTML, intFontSizeStartPos, 1) = "+" Then
                    intFontSizeStartPos = intFontSizeStartPos + 1
                    intFontSize = 11 + 2 * Mid$(strHTML, intFontSizeStartPos, intFontSizeEndPos - intFontSizeStartPos + 1)
                ElseIf Mid$(strHTML, intFontSizeStartPos, 1) = "-" Then
                    intFontSizeStartPos = intFontSizeStartPos + 1
                    intFontSize = 11 - 2 * Mid$(strHTML, intFontSizeStartPos, intFontSizeEndPos - intFontSizeStartPos + 1)
                Else
                    intFontSize = Mid$(strHTML, intFontSizeStartPos, intFontSizeEndPos - intFontSizeStartPos + 1)
                End If
            Else
                ' Error!
                GoTo HTML_Err
            End If
            intEndPos = InStr(intSrcPos, strHTML, ">")
            intSrcPos = intEndPos + 1
            intStartPos = intSrcPos
            If intSrcPos > Len(strHTML) Then Exit Do
            While intDestSrcEquiv(intStartPos) = 0 And intStartPos < Len(strHTML)
                intStartPos = intStartPos + 1
            Wend
            If intStartPos >= Len(strHTML) Then GoTo HTML_Err ' HTML is bad!
            varEndTag = "</font>"
            intEndPos = InStr(intSrcPos, LCase(strHTML), varEndTag)
            If intEndPos = 0 Then GoTo HTML_Err ' HTML is bad!
            While intDestSrcEquiv(intEndPos) = 0 And intEndPos > intSrcPos
                intEndPos = intEndPos - 1
            Wend
            If intEndPos > intSrcPos Then
                intActualStartPos = intDestSrcEquiv(intStartPos)
                intActualEndPos = intDestSrcEquiv(intEndPos)
                rngA.Characters(intActualStartPos, intActualEndPos - intActualStartPos + 1) _
                    .Font.Size = intFontSize
            End If
        End If
        intSrcPos = intSrcPos + 1
    Loop

    'Now do remaining tags
    intSrcPos = 1
    intDestPos = 1
    Do While intSrcPos <= Len(strHTML)
        If intDestSrcEquiv(intSrcPos) = 0 Then
            ' This must be a Tag!
            For intCtr = 0 To UBound(varyTags) Step 2
                varTag = varyTags(intCtr)
                intStartPos = intSrcPos + Len(varTag)
                While intDestSrcEquiv(intStartPos) = 0 And intStartPos < Len(strHTML)
                    intStartPos = intStartPos + 1
                Wend
                If intStartPos >= Len(strHTML) Then GoTo HTML_Err ' HTML is bad!
                If LCase(Mid$(strHTML, intSrcPos, Len(varTag))) = varTag Then
                    varEndTag = varyTags(intCtr + 1)
                    intEndPos = InStr(intSrcPos, LCase(strHTML), varEndTag)
                    If intEndPos = 0 Then GoTo HTML_Err ' HTML is bad!
                    While intDestSrcEquiv(intEndPos) = 0 And intEndPos > intSrcPos
                        intEndPos = intEndPos - 1
                    Wend
                    If intEndPos > intSrcPos Then
                        intActualStartPos = intDestSrcEquiv(intStartPos)
                        intActualEndPos = intDestSrcEquiv(intEndPos)
                        With rngA.Characters(intActualStartPos, intActualEndPos - intActualStartPos + 1).Font
                            If varTag = "<b>" Then
                                .Bold = True
                            ElseIf varTag = "<i>" Then
                                .Italic = True
                            ElseIf varTag = "<u>" Then
                                .Underline = True
                            ElseIf varTag = "<sup>" Then
                                .Superscript = True
                            ElseIf varTag = "<sub>" Then
                                .Subscript = True
                            End If
                        End With
                    End If
                    intSrcPos = intSrcPos + Len(varTag) - 1
                    Exit For
                End If
            Next
        End If
        intSrcPos = intSrcPos + 1
        intDestPos = intDestPos + 1
    Loop
Exit_Sub:
    Exit Sub
HTML_Err:
    ' There was an error with the Tags. Show warning if requested.
    If blnShowBadHTMLWarning Then
        MsgBox "There was an error with the Tags in the HTML file. Could not apply formatting."
    End If
End Sub

Note this doesn't care about tag nesting, instead only requiring a close tag for every open tag, and assuming the close tag nearest the opening tag applies to the opening tag. Properly nested tags will work fine, while improperly nested tags will not be rejected and may or may not work.

Parse an HTML string with JS

The fastest way to parse HTML in Chrome and Firefox is Range#createContextualFragment:

var range = document.createRange();
range.selectNode(document.body); // required in Safari
var fragment = range.createContextualFragment('<h1>html...</h1>');
var firstNode = fragment.firstChild;

I would recommend to create a helper function which uses createContextualFragment if available and falls back to innerHTML otherwise.

Benchmark: http://jsperf.com/domparser-vs-createelement-innerhtml/3

How to extract img src, title and alt from html using php?

EDIT : now that I know better

Using regexp to solve this kind of problem is a bad idea and will likely lead in unmaintainable and unreliable code. Better use an HTML parser.

Solution With regexp

In that case it's better to split the process into two parts :

  • get all the img tag
  • extract their metadata

I will assume your doc is not xHTML strict so you can't use an XML parser. E.G. with this web page source code :

/* preg_match_all match the regexp in all the $html string and output everything as 
an array in $result. "i" option is used to make it case insensitive */

preg_match_all('/<img[^>]+>/i',$html, $result); 

print_r($result);
Array
(
    [0] => Array
        (
            [0] => <img src="/Content/Img/stackoverflow-logo-250.png" width="250" height="70" alt="logo link to homepage" />
            [1] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />
            [2] => <img class="vote-down" src="/content/img/vote-arrow-down.png" alt="vote down" title="This was not helpful (click again to undo)" />
            [3] => <img src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG" height=32 width=32 alt="gravatar image" />
            [4] => <img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />

[...]
        )

)

Then we get all the img tag attributes with a loop :

$img = array();
foreach( $result as $img_tag)
{
    preg_match_all('/(alt|title|src)=("[^"]*")/i',$img_tag, $img[$img_tag]);
}

print_r($img);

Array
(
    [<img src="/Content/Img/stackoverflow-logo-250.png" width="250" height="70" alt="logo link to homepage" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/Content/Img/stackoverflow-logo-250.png"
                    [1] => alt="logo link to homepage"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                )

            [2] => Array
                (
                    [0] => "/Content/Img/stackoverflow-logo-250.png"
                    [1] => "logo link to homepage"
                )

        )

    [<img class="vote-up" src="/content/img/vote-arrow-up.png" alt="vote up" title="This was helpful (click again to undo)" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/content/img/vote-arrow-up.png"
                    [1] => alt="vote up"
                    [2] => title="This was helpful (click again to undo)"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                    [2] => title
                )

            [2] => Array
                (
                    [0] => "/content/img/vote-arrow-up.png"
                    [1] => "vote up"
                    [2] => "This was helpful (click again to undo)"
                )

        )

    [<img class="vote-down" src="/content/img/vote-arrow-down.png" alt="vote down" title="This was not helpful (click again to undo)" />] => Array
        (
            [0] => Array
                (
                    [0] => src="/content/img/vote-arrow-down.png"
                    [1] => alt="vote down"
                    [2] => title="This was not helpful (click again to undo)"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                    [2] => title
                )

            [2] => Array
                (
                    [0] => "/content/img/vote-arrow-down.png"
                    [1] => "vote down"
                    [2] => "This was not helpful (click again to undo)"
                )

        )

    [<img src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG" height=32 width=32 alt="gravatar image" />] => Array
        (
            [0] => Array
                (
                    [0] => src="http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG"
                    [1] => alt="gravatar image"
                )

            [1] => Array
                (
                    [0] => src
                    [1] => alt
                )

            [2] => Array
                (
                    [0] => "http://www.gravatar.com/avatar/df299babc56f0a79678e567e87a09c31?s=32&d=identicon&r=PG"
                    [1] => "gravatar image"
                )

        )

   [..]
        )

)

Regexps are CPU intensive so you may want to cache this page. If you have no cache system, you can tweak your own by using ob_start and loading / saving from a text file.

How does this stuff work ?

First, we use preg_ match_ all, a function that gets every string matching the pattern and ouput it in it's third parameter.

The regexps :

<img[^>]+>

We apply it on all html web pages. It can be read as every string that starts with "<img", contains non ">" char and ends with a >.

(alt|title|src)=("[^"]*")

We apply it successively on each img tag. It can be read as every string starting with "alt", "title" or "src", then a "=", then a ' " ', a bunch of stuff that are not ' " ' and ends with a ' " '. Isolate the sub-strings between ().

Finally, every time you want to deal with regexps, it handy to have good tools to quickly test them. Check this online regexp tester.

EDIT : answer to the first comment.

It's true that I did not think about the (hopefully few) people using single quotes.

Well, if you use only ', just replace all the " by '.

If you mix both. First you should slap yourself :-), then try to use ("|') instead or " and [^ø] to replace [^"].

Regex select all text between tags

In Python, setting the DOTALL flag will capture everything, including newlines.

If the DOTALL flag has been specified, this matches any character including a newline. docs.python.org

#example.py using Python 3.7.4  
import re

str="""Everything is awesome! <pre>Hello,
World!
    </pre>
"""

# Normally (.*) will not capture newlines, but here re.DOTATLL is set 
pattern = re.compile(r"<pre>(.*)</pre>",re.DOTALL)
matches = pattern.search(str)

print(matches.group(1))

python example.py

Hello,
World!

Capturing text between all opening and closing tags in a document

To capture text between all opening and closing tags in a document, finditer is useful. In the example below, three opening and closing <pre> tags are present in the string.

#example2.py using Python 3.7.4
import re

# str contains three <pre>...</pre> tags
str = """In two different ex-
periments, the authors had subjects chat and solve the <pre>Desert Survival Problem</pre> with a
humorous or non-humorous computer. In both experiments the computer made pre-
programmed comments, but in study 1 subjects were led to believe they were interact-
ing with another person. In the <pre>humor conditions</pre> subjects received a number of funny
comments, for instance: “The mirror is probably too small to be used as a signaling
device to alert rescue teams to your location. Rank it lower. (On the other hand, it
offers <pre>endless opportunity for self-reflection</pre>)”."""

# Normally (.*) will not capture newlines, but here re.DOTATLL is set
# The question mark in (.*?) indicates non greedy matching.
pattern = re.compile(r"<pre>(.*?)</pre>",re.DOTALL)

matches = pattern.finditer(str)


for i,match in enumerate(matches):
    print(f"tag {i}: ",match.group(1))

python example2.py

tag 0:  Desert Survival Problem
tag 1:  humor conditions
tag 2:  endless opportunity for self-reflection

How to strip HTML tags from string in JavaScript?

Using the browser's parser is the probably the best bet in current browsers. The following will work, with the following caveats:

  • Your HTML is valid within a <div> element. HTML contained within <body> or <html> or <head> tags is not valid within a <div> and may therefore not be parsed correctly.
  • textContent (the DOM standard property) and innerText (non-standard) properties are not identical. For example, textContent will include text within a <script> element while innerText will not (in most browsers). This only affects IE <=8, which is the only major browser not to support textContent.
  • The HTML does not contain <script> elements.
  • The HTML is not null
  • The HTML comes from a trusted source. Using this with arbitrary HTML allows arbitrary untrusted JavaScript to be executed. This example is from a comment by Mike Samuel on the duplicate question: <img onerror='alert(\"could run arbitrary JS here\")' src=bogus>

Code:

var html = "<p>Some HTML</p>";
var div = document.createElement("div");
div.innerHTML = html;
var text = div.textContent || div.innerText || "";

PHP: HTML: send HTML select option attribute in POST

You can use jquery function.

<form name='add'>
   <input type='text' name='stud_name' id="stud_name" value=""/>
   Age: <select name='age' id="age">
   <option value='1' stud_name='sre'>23</option>
   <option value='2' stud_name='sam'>24</option>
   <option value='5' stud_name='john'>25</option>
   </select>
   <input type='submit' name='submit'/>
</form>

jquery code :

<script type="text/javascript" src="jquery.js"></script>

<script>
    $(function() {
          $("#age").change(function(){
          var option = $('option:selected', this).attr('stud_name');
          $('#stud_name').val(option);
       });
    });
</script>

Parsing HTML using Python

Compared to the other parser libraries lxml is extremely fast:

And with cssselect it’s quite easy to use for scraping HTML pages too:

from lxml.html import parse
doc = parse('http://www.google.com').getroot()
for div in doc.cssselect('a'):
    print '%s: %s' % (div.text_content(), div.get('href'))

lxml.html Documentation

How do I parse a HTML page with Node.js

November 2020 Update

I searched for the top NodeJS html parser libraries.

Because my use cases didn't require a library with many features, I could focus on stability and performance.

By stability I mean that I want the library to be used long enough by the community in order to find bugs and that it will be still maintained and that open issues will be closed.

Its hard to understand the future of an open source library, but I did a small summary based on the top 10 libraries in openbase.

I divided into 2 groups according to the last commit (and on each group the order is according to Github starts):

Last commit is in the last 6 months:

jsdom - Last commit: 3 Months, Open issues: 331, Github stars: 14.9K.

htmlparser2 - Last commit: 8 days, Open issues: 2, Github stars: 2.7K.

parse5 - Last commit: 2 Months, Open issues: 21, Github stars: 2.5K.

swagger-parser - Last commit: 2 Months, Open issues: 48, Github stars: 663.

html-parse-stringify - Last commit: 4 Months, Open issues: 3, Github stars: 215.

node-html-parser - Last commit: 7 days, Open issues: 15, Github stars: 205.

Last commit is 6 months and above:

cheerio - Last commit: 1 year, Open issues: 174, Github stars: 22.9K.

koa-bodyparser - Last commit: 6 months, Open issues: 9, Github stars: 1.1K.

sax-js - Last commit: 3 Years, Open issues: 65, Github stars: 941.

draftjs-to-html - Last commit: 1 Year, Open issues: 27, Github stars: 233.

I picked Node-html-parser because it seems quiet fast and very active at this moment.

(*) Openbase adds much more information regarding each library like the number of contributors (with +3 commits), weekly downloads, Monthly commits, Version etc'.

(**) The table above is a snapshot according to the specific time and date - I would check the reference again and as a first step check the level of recent activity and then dive into the smaller details.

How to extract string following a pattern with grep, regex or perl

Since you need to match content without including it in the result (must match name=" but it's not part of the desired result) some form of zero-width matching or group capturing is required. This can be done easily with the following tools:

Perl

With Perl you could use the n option to loop line by line and print the content of a capturing group if it matches:

perl -ne 'print "$1\n" if /name="(.*?)"/' filename

GNU grep

If you have an improved version of grep, such as GNU grep, you may have the -P option available. This option will enable Perl-like regex, allowing you to use \K which is a shorthand lookbehind. It will reset the match position, so anything before it is zero-width.

grep -Po 'name="\K.*?(?=")' filename

The o option makes grep print only the matched text, instead of the whole line.

Vim - Text Editor

Another way is to use a text editor directly. With Vim, one of the various ways of accomplishing this would be to delete lines without name= and then extract the content from the resulting lines:

:v/.*name="\v([^"]+).*/d|%s//\1

Standard grep

If you don't have access to these tools, for some reason, something similar could be achieved with standard grep. However, without the look around it will require some cleanup later:

grep -o 'name="[^"]*"' filename

A note about saving results

In all of the commands above the results will be sent to stdout. It's important to remember that you can always save them by piping it to a file by appending:

> result

to the end of the command.

How can I use the python HTMLParser library to extract data from a specific div tag?

This works perfectly:

print (soup.find('the tag').text)

Which HTML Parser is the best?

Self plug: I have just released a new Java HTML parser: jsoup. I mention it here because I think it will do what you are after.

Its party trick is a CSS selector syntax to find elements, e.g.:

String html = "<html><head><title>First parse</title></head>"
  + "<body><p>Parsed HTML into a doc.</p></body></html>";
Document doc = Jsoup.parse(html);
Elements links = doc.select("a");
Element head = doc.select("head").first();

See the Selector javadoc for more info.

This is a new project, so any ideas for improvement are very welcome!

Read a HTML file into a string variable in memory

You can do it the simple way:

string pathToHTMLFile = @"C:\temp\someFile.html";
string htmlString = File.ReadAllText(pathToHTMLFile);

Or you could stream it in with FileStream/StreamReader:

using (FileStream fs = File.Open(pathToHTMLFile, FileMode.Open, FileAccess.ReadWrite))
{
    using (StreamReader sr = new StreamReader(fs))
    {
        htmlString = sr.ReadToEnd();
    }
}

This latter method allows you to open the file while still permitting others to perform Read/Write operations on the file. I can't imagine an HTML file being very big, but it has the added benefit of streaming the file instead of capturing it as one large chunk like the first method.

How do you parse and process HTML/XML in PHP?

Yes you can use simple_html_dom for the purpose. However I have worked quite a lot with the simple_html_dom, particularly for web scraping and have found it to be too vulnerable. It does the basic job but I won't recommend it anyways.

I have never used curl for the purpose but what I have learned is that curl can do the job much more efficiently and is much more solid.

Kindly check out this link:scraping-websites-with-curl

HTML Agility pack - parsing tables

In my case, there is a single table which happens to be a device list from a router. If you wish to read the table using TR/TH/TD (row, header, data) instead of a matrix as mentioned above, you can do something like the following:

    List<TableRow> deviceTable = (from table in document.DocumentNode.SelectNodes(XPathQueries.SELECT_TABLE)
                                       from row in table?.SelectNodes(HtmlBody.TR)
                                       let rows = row.SelectSingleNode(HtmlBody.TR)
                                       where row.FirstChild.OriginalName != null && row.FirstChild.OriginalName.Equals(HtmlBody.T_HEADER)
                                       select new TableRow
                                       {
                                           Header = row.SelectSingleNode(HtmlBody.T_HEADER)?.InnerText,
                                           Data = row.SelectSingleNode(HtmlBody.T_DATA)?.InnerText}).ToList();
                                       }

TableRow is just a simple object with Header and Data as properties. The approach takes care of null-ness and this case:

_x000D_
_x000D_ 
<tr>_x000D_
    <td width="28%">&nbsp;</td>_x000D_
</tr>
_x000D_
_x000D_
_x000D_

which is row without a header. The HtmlBody object with the constants hanging off of it are probably readily deduced but I apologize for it even still. I came from the world where if you have " in your code, it should either be constant or localizable.

Converting a sentence string to a string array of words in Java

You can just split your string like that using this regular expression

String l = "sofia, malgré tout aimait : la laitue et le choux !" <br/>
l.split("[[ ]*|[,]*|[\\.]*|[:]*|[/]*|[!]*|[?]*|[+]*]+");

How do I limit the number of results returned from grep?

Another option is just using head:

grep ...parameters... yourfile | head

This won't require searching the entire file - it will stop when the first ten matching lines are found. Another advantage with this approach is that will return no more than 10 lines even if you are using grep with the -o option.

For example if the file contains the following lines:

112233
223344
123123

Then this is the difference in the output:

$ grep -o '1.' yourfile | head -n2
11
12

$ grep -m2 -o '1.'
11
12
12

Using head returns only 2 results as desired, whereas -m2 returns 3.

Charts for Android

SciChart for Android is a relative newcomer, but brings extremely fast high performance real-time charting to the Android platform.

SciChart is a commercial control but available under royalty free distribution / per developer licensing. There is also free licensing available for educational use with some conditions.

Some useful links can be found below:

enter image description here

Disclosure: I am the tech lead on the SciChart project!

Java: how to convert HashMap<String, Object> to array

If you are using Java 8+ and need a 2 dimensional Array, perhaps for TestNG data providers, you can try:

map.entrySet()
    .stream()
    .map(e -> new Object[]{e.getKey(), e.getValue()})
    .toArray(Object[][]::new);

If your Objects are Strings and you need a String[][], try:

map.entrySet()
    .stream()
    .map(e -> new String[]{e.getKey(), e.getValue().toString()})
    .toArray(String[][]::new);

Facebook Open Graph not clearing cache

The OG thumbnail does not seem to refresh even if passing the fbrefresh variable. To update this without waiting for automated clearing you'll need to change the filename of the thumbnail associated meta tag value and refresh.

How can I make directory writable?

  • chmod +w <directory> or chmod a+w <directory> - Write permission for user, group and others

  • chmod u+w <directory> - Write permission for user

  • chmod g+w <directory> - Write permission for group

  • chmod o+w <directory> - Write permission for others

What is the Swift equivalent to Objective-C's "@synchronized"?

Figure I'll post my Swift 5 implementation, built off of the prior answers. Thanks guys! I found it helpful to have one that returns a value too, so I have two methods.

Here is a simple class to make first:

import Foundation
class Sync {
public class func synced(_ lock: Any, closure: () -> ()) {
        objc_sync_enter(lock)
        defer { objc_sync_exit(lock) }
        closure()
    }
    public class func syncedReturn(_ lock: Any, closure: () -> (Any?)) -> Any? {
        objc_sync_enter(lock)
        defer { objc_sync_exit(lock) }
        return closure()
    }
}

Then use it like so if needing a return value: 

return Sync.syncedReturn(self, closure: {
    // some code here
    return "hello world"
})

Or:

Sync.synced(self, closure: {
    // do some work synchronously
})

Restrict varchar() column to specific values?

When you are editing a table
Right Click -> Check Constraints -> Add -> Type something like Frequency IN ('Daily', 'Weekly', 'Monthly', 'Yearly') in expression field and a good constraint name in (Name) field.
You are done.

Daemon Threads Explanation

Let's say you're making some kind of dashboard widget. As part of this, you want it to display the unread message count in your email box. So you make a little thread that will:

  1. Connect to the mail server and ask how many unread messages you have.
  2. Signal the GUI with the updated count.
  3. Sleep for a little while.

When your widget starts up, it would create this thread, designate it a daemon, and start it. Because it's a daemon, you don't have to think about it; when your widget exits, the thread will stop automatically.

ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean

Similar to the solution of making sure org.springframework.boot:spring-boot-starter-tomcat was installed, I was missing org.eclipse.jetty:jetty-server from my build.gradle

org.springframework.boot:spring-boot-starter-web needs a server be it Tomcat, Jetty or something else - it will compile but not run without one.

HTTP Status 500 - org.apache.jasper.JasperException: java.lang.NullPointerException

NullPointerException with JSP can also happen if:

A getter returns a non-public inner class.

This code will fail if you remove Getters's access modifier or make it private or protected.

JAVA:

package com.myPackage;
public class MyClass{ 
    //: Must be public or you will get:
    //: org.apache.jasper.JasperException: 
    //: java.lang.NullPointerException
    public class Getters{
        public String 
        myProperty(){ return(my_property); }
    };;

    //: JSP EL can only access functions:
    private Getters _get;
    public  Getters  get(){ return _get; }

    private String 
    my_property;

    public MyClass(String my_property){
        super();
        this.my_property    = my_property;
        _get = new Getters();
    };;
};;

JSP

<%@ taglib uri   ="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ page import="com.myPackage.MyClass" %>
<%
    MyClass inst = new MyClass("[PROP_VALUE]");
    pageContext.setAttribute("my_inst", inst ); 
%><html lang="en"><body>
    ${ my_inst.get().myProperty() }
</body></html>

What is the order of precedence for CSS?

Also important to note is that when you have two styles on an HTML element with equal precedence, the browser will give precedence to the styles that were written to the DOM last ... so if in the DOM:

<html>
<head>
<style>.container-ext { width: 100%; }</style>
<style>.container { width: 50px; }</style>
</head>
<body>
<div class="container container-ext">Hello World</div>
</body>

...the width of the div will be 50px

How do I get logs from all pods of a Kubernetes replication controller?

I use this simple script to get a log from the pods of a deployment:

#!/usr/bin/env bash

DEPLOYMENT=$1

for p in $(kubectl get pods | grep ^${DEPLOYMENT}- | cut -f 1 -d ' '); do 
    echo --------------------------- 
    echo $p 
    echo --------------------------- 
    kubectl logs $p
done

Gist of the script

Usage: log_deployment.sh "deployment-name".

Script will then show log of all pods that start with that "deployment-name".

Fatal error: Uncaught Error: Call to undefined function mysql_connect()

mysql_* functions have been removed in PHP 7.

You now have two alternatives: MySQLi and PDO.

The following is a before (-) and after (+) comparison of a migration to the MySQLi alternative, taken straight out of working code:

-if (!$dbLink = mysql_connect($dbHost, $dbUser, $dbPass))
+if (!$dbLink = mysqli_connect($dbHost, $dbUser, $dbPass))

-if (!mysql_select_db($dbName, $dbLink))
+if (!mysqli_select_db($dbLink, $dbName))

-if (!$result = mysql_query($query, $dbLink)) {
+if (!$result = mysqli_query($dbLink, $query)) {

-if (mysql_num_rows($result) > 0) {
+if (mysqli_num_rows($result) > 0) {

-while ($row = mysql_fetch_array( $result, MYSQL_ASSOC )) {
+while ($row = mysqli_fetch_array( $result, MYSQLI_ASSOC )) {

-mysql_close($dbLink);
+mysqli_close($dbLink);

How are echo and print different in PHP?

They are:

  • print only takes one parameter, while echo can have multiple parameters.
  • print returns a value (1), so can be used as an expression.
  • echo is slightly faster.

Sorting dictionary keys in python

 
my_list = sorted(dict.items(), key=lambda x: x[1])

Get Substring between two characters using javascript

If you want to extract all substrings from a string, that occur between two delimiters (different or same), you can use this function. It returns an array with all substrings found:

function get_substrings_between(str, startDelimiter, endDelimiter) 
{
    var contents = [];
    var startDelimiterLength = startDelimiter.length;
    var endDelimiterLength = endDelimiter.length;
    var startFrom = contentStart = contentEnd = 0;
    
    while(false !== (contentStart = strpos(str, startDelimiter, startFrom))) 
    {
        contentStart += startDelimiterLength;
        contentEnd = strpos(str, endDelimiter, contentStart);
        if(false === contentEnd) 
        {
            break;
        }
        contents.push( str.substr(contentStart, contentEnd - contentStart) );
        startFrom = contentEnd + endDelimiterLength;
    }

    return contents;
}

// https://stackoverflow.com/a/3978237/1066234
function strpos(haystack, needle, offset) 
{
    var i = (haystack+'').indexOf(needle, (offset || 0));
    return i === -1 ? false : i;
}

// Example usage
var string = "We want to extract all infos (essential ones) from within the brackets (this should be fun).";
var extracted = get_substrings_between(string, '(', ')');
console.log(extracted); 
// output: (2) ["essential ones", "this should be fun"]

Orginally from PHP by raina77ow, ported to Javascript.

Classes vs. Functions

I'm going to break from the herd on this one and provide an alternate point of view:

Never create classes.

Reliance on classes has a significant tendency to cause coders to create bloated and slow code. Classes getting passed around (since they're objects) take a lot more computational power than calling a function and passing a string or two. Proper naming conventions on functions can do pretty much everything creating a class can do, and with only a fraction of the overhead and better code readability.

That doesn't mean you shouldn't learn to understand classes though. If you're coding with others, people will use them all the time and you'll need to know how to juggle those classes. Writing your code to rely on functions means the code will be smaller, faster, and more readable. I've seen huge sites written using only functions that were snappy and quick, and I've seen tiny sites that had minimal functionality that relied heavily on classes and broke constantly. (When you have classes extending classes that contain classes as part of their classes, you know you've lost all semblance of easy maintainability.)

When it comes down to it, all data you're going to want to pass can easily be handled by the existing datatypes.

Classes were created as a mental crutch and provide no actual extra functionality, and the overly-complicated code they have a tendency to create defeats the point of that crutch in the long run.

How to start working with GTest and CMake

The solution involved putting the gtest source directory as a subdirectory of your project. I've included the working CMakeLists.txt below if it is helpful to anyone. 

cmake_minimum_required(VERSION 2.6)
project(basic_test)

################################
# GTest
################################
ADD_SUBDIRECTORY (gtest-1.6.0)
enable_testing()
include_directories(${gtest_SOURCE_DIR}/include ${gtest_SOURCE_DIR})

################################
# Unit Tests
################################
# Add test cpp file
add_executable( runUnitTests testgtest.cpp )
# Link test executable against gtest & gtest_main
target_link_libraries(runUnitTests gtest gtest_main)
add_test( runUnitTests runUnitTests )

Python JSON serialize a Decimal object

From the JSON Standard Document, as linked in json.org:

JSON is agnostic about the semantics of numbers. In any programming language, there can be a variety of number types of various capacities and complements, fixed or floating, binary or decimal. That can make interchange between different programming languages difficult. JSON instead offers only the representation of numbers that humans use: a sequence of digits. All programming languages know how to make sense of digit sequences even if they disagree on internal representations. That is enough to allow interchange.

So it's actually accurate to represent Decimals as numbers (rather than strings) in JSON. Bellow lies a possible solution to the problem.

Define a custom JSON encoder:

import json


class CustomJsonEncoder(json.JSONEncoder):

    def default(self, obj):
        if isinstance(obj, Decimal):
            return float(obj)
        return super(CustomJsonEncoder, self).default(obj)

Then use it when serializing your data:

json.dumps(data, cls=CustomJsonEncoder)

As noted from comments on the other answers, older versions of python might mess up the representation when converting to float, but that's not the case anymore.

To get the decimal back in Python:

Decimal(str(value))

This solution is hinted in Python 3.0 documentation on decimals:

To create a Decimal from a float, first convert it to a string.

DateTimePicker time picker in 24 hour but displaying in 12hr?

I know it's been quite some time since the question was asked. However, if it helps anyone this worked for me.

 $(function() {
    $('.datetimepicker').datetimepicker({
        format: 'MM-DD-YYYY HH:mm '
    });
});

Why am I getting "Thread was being aborted" in ASP.NET?

For a web service hosted in ASP.NET, the configuration property is executionTimeout:

<configuration> <system.web>

<httpRuntime executionTimeout="360" />

</system.web>

</configuration>

Set this and the thread abort exception will go away :)

executing a function in sql plus

One option would be:

SET SERVEROUTPUT ON

EXEC DBMS_OUTPUT.PUT_LINE(your_fn_name(your_fn_arguments));

Can HTTP POST be limitless?

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

n-grams in python, four, five, six grams?

If you want a pure iterator solution for large strings with constant memory usage:

from typing import Iterable  
import itertools

def ngrams_iter(input: str, ngram_size: int, token_regex=r"[^\s]+") -> Iterable[str]:
    input_iters = [ 
        map(lambda m: m.group(0), re.finditer(token_regex, input)) 
        for n in range(ngram_size) 
    ]
    # Skip first words
    for n in range(1, ngram_size): list(map(next, input_iters[n:]))  

    output_iter = itertools.starmap( 
        lambda *args: " ".join(args),  
        zip(*input_iters) 
    ) 
    return output_iter

Test:

input = "If you want a pure iterator solution for large strings with constant memory usage"
list(ngrams_iter(input, 5))

Output:

['If you want a pure',
 'you want a pure iterator',
 'want a pure iterator solution',
 'a pure iterator solution for',
 'pure iterator solution for large',
 'iterator solution for large strings',
 'solution for large strings with',
 'for large strings with constant',
 'large strings with constant memory',
 'strings with constant memory usage']

How to start nginx via different port(other than 80)

You will need to change the configure port of either Apache or Nginx. After you do this you will need to restart the reconfigured servers, using the 'service' command you used.

Apache

Edit

sudo subl /etc/apache2/ports.conf

and change the 80 on the following line to something different :

Listen 80

If you just change the port or add more ports here, you will likely also have to change the VirtualHost statement in

sudo subl /etc/apache2/sites-enabled/000-default.conf

and change the 80 on the following line to something different :

<VirtualHost *:80>

then restart by :

sudo service apache2 restart

Nginx

Edit 

/etc/nginx/sites-enabled/default

and change the 80 on the following line :

listen 80;

then restart by :

sudo service nginx restart

Failed to serialize the response in Web API with Json

When it comes to returning data back to the consumer from Web Api (or any other web service for that matter), I highly recommend not passing back entities that come from a database. It is much more reliable and maintainable to use Models in which you have control of what the data looks like and not the database. That way you don't have to mess around with the formatters so much in the WebApiConfig. You can just create a UserModel that has child Models as properties and get rid of the reference loops in the return objects. That makes the serializer much happier.

Also, it isn't necessary to remove formatters or supported media types typically if you are just specifying the "Accepts" header in the request. Playing around with that stuff can sometimes make things more confusing.

Example:

public class UserModel {
    public string Name {get;set;}
    public string Age {get;set;}
    // Other properties here that do not reference another UserModel class.
}

Convert unix time stamp to date in java

You can use SimlpeDateFormat to format your date like this:

long unixSeconds = 1372339860;
// convert seconds to milliseconds
Date date = new java.util.Date(unixSeconds*1000L); 
// the format of your date
SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss z"); 
// give a timezone reference for formatting (see comment at the bottom)
sdf.setTimeZone(java.util.TimeZone.getTimeZone("GMT-4")); 
String formattedDate = sdf.format(date);
System.out.println(formattedDate);

The pattern that SimpleDateFormat takes if very flexible, you can check in the javadocs all the variations you can use to produce different formatting based on the patterns you write given a specific Date. http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html

  • Because a Date provides a getTime() method that returns the milliseconds since EPOC, it is required that you give to SimpleDateFormat a timezone to format the date properly acording to your timezone, otherwise it will use the default timezone of the JVM (which if well configured will anyways be right)

How do you get the current project directory from C# code when creating a custom MSBuild task?

If you want ot know what is the directory where your solution is located, you need to do this:

 var parent = Directory.GetParent(Directory.GetCurrentDirectory()).Parent;
            if (parent != null)
            {
                var directoryInfo = parent.Parent;
                string startDirectory = null;
                if (directoryInfo != null)
                {
                    startDirectory = directoryInfo.FullName;
                }
                if (startDirectory != null)
                { /*Do whatever you want "startDirectory" variable*/}
            }

If you let only with GetCurrrentDirectory() method, you get the build folder no matter if you are debugging or releasing. I hope this help! If you forget about validations it would be like this:

var startDirectory = Directory.GetParent(Directory.GetCurrentDirectory()).Parent.Parent.FullName;

Using comma as list separator with AngularJS

_x000D_
_x000D_ 
.list-comma::before {_x000D_
  content: ',';_x000D_
}_x000D_
.list-comma:first-child::before {_x000D_
  content: '';_x000D_
}
_x000D_ 
<span class="list-comma" ng-repeat="destination in destinations">_x000D_
                            {{destination.name}}_x000D_
                        </span>
_x000D_
_x000D_
_x000D_

Where to place the 'assets' folder in Android Studio?

In Android Studio 4.1.1

Right Click on your module (app for example) -> New -> Folder -> Assets Folder

enter image description here

How do I execute a string containing Python code in Python?

eval and exec are the correct solution, and they can be used in a safer manner.

As discussed in Python's reference manual and clearly explained in this tutorial, the eval and exec functions take two extra parameters that allow a user to specify what global and local functions and variables are available.

For example:

public_variable = 10

private_variable = 2

def public_function():
    return "public information"

def private_function():
    return "super sensitive information"

# make a list of safe functions
safe_list = ['public_variable', 'public_function']
safe_dict = dict([ (k, locals().get(k, None)) for k in safe_list ])
# add any needed builtins back in
safe_dict['len'] = len

>>> eval("public_variable+2", {"__builtins__" : None }, safe_dict)
12

>>> eval("private_variable+2", {"__builtins__" : None }, safe_dict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'private_variable' is not defined

>>> exec("print \"'%s' has %i characters\" % (public_function(), len(public_function()))", {"__builtins__" : None}, safe_dict)
'public information' has 18 characters

>>> exec("print \"'%s' has %i characters\" % (private_function(), len(private_function()))", {"__builtins__" : None}, safe_dict)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'private_function' is not defined

In essence you are defining the namespace in which the code will be executed.

How to write data to a text file without overwriting the current data

You have to open as new StreamWriter(filename, true) so that it appends to the file instead of overwriting.

Detect browser or tab closing

Try to use it:

window.onbeforeunload = function (event) {
    var message = 'Important: Please click on \'Save\' button to leave this page.';
    if (typeof event == 'undefined') {
        event = window.event;
    }
    if (event) {
        event.returnValue = message;
    }
    return message;
};

$(function () {
    $("a").not('#lnkLogOut').click(function () {
        window.onbeforeunload = null;
    });
    $(".btn").click(function () {
        window.onbeforeunload = null;
});
});

Datagridview full row selection but get single cell value

I know, I'm a little late for the answer. But I would like to contribute.

DataGridView.SelectedRows[0].Cells[0].Value

This code is simple as piece of cake

How do I link object files in C? Fails with "Undefined symbols for architecture x86_64"

Add foo1.c , foo2.c , foo3.c and makefile in one folder the type make in bash

if you do not want to use the makefile, you can run the command

gcc -c foo1.c foo2.c foo3.c

then

gcc -o output foo1.o foo2.o foo3.o

foo1.c

#include <stdio.h>
#include <string.h>

void funk1();

void funk1() {
    printf ("\nfunk1\n");
}


int main(void) {

    char *arg2;
    size_t nbytes = 100;

    while ( 1 ) {

        printf ("\nargv2 = %s\n" , arg2);
        printf ("\n:> ");
        getline (&arg2 , &nbytes , stdin);
        if( strcmp (arg2 , "1\n") == 0 ) {
            funk1 ();
        } else if( strcmp (arg2 , "2\n") == 0 ) {
            funk2 ();
        } else if( strcmp (arg2 , "3\n") == 0 ) {
            funk3 ();
        } else if( strcmp (arg2 , "4\n") == 0 ) {
            funk4 ();
        } else {
            funk5 ();
        }
    }
}

foo2.c

#include <stdio.h>
void funk2(){
    printf("\nfunk2\n");
}
void funk3(){
    printf("\nfunk3\n");
}

foo3.c

#include <stdio.h>

void funk4(){
    printf("\nfunk4\n");
}
void funk5(){
    printf("\nfunk5\n");
}

makefile

outputTest: foo1.o foo2.o foo3.o
    gcc -o output foo1.o foo2.o foo3.o
    make removeO

outputTest.o: foo1.c foo2.c foo3.c
    gcc -c foo1.c foo2.c foo3.c

clean:
    rm -f *.o output

removeO:
    rm -f *.o

How to return a string value from a Bash function

Bash, since version 4.3, feb 2014(?), has explicit support for reference variables or name references (namerefs), beyond "eval", with the same beneficial performance and indirection effect, and which may be clearer in your scripts and also harder to "forget to 'eval' and have to fix this error":

declare [-aAfFgilnrtux] [-p] [name[=value] ...]
typeset [-aAfFgilnrtux] [-p] [name[=value] ...]
  Declare variables and/or give them attributes
  ...
  -n Give each name the nameref attribute, making it a name reference
     to another variable.  That other variable is defined by the value
     of name.  All references and assignments to name, except for·
     changing the -n attribute itself, are performed on the variable
     referenced by name's value.  The -n attribute cannot be applied to
     array variables.
...
When used in a function, declare and typeset make each name local,
as with the local command, unless the -g option is supplied...

and also:

PARAMETERS

A variable can be assigned the nameref attribute using the -n option to the declare or local builtin commands (see the descriptions of declare and local below) to create a nameref, or a reference to another variable. This allows variables to be manipulated indirectly. Whenever the nameref variable is· referenced or assigned to, the operation is actually performed on the variable specified by the nameref variable's value. A nameref is commonly used within shell functions to refer to a variable whose name is passed as an argument to· the function. For instance, if a variable name is passed to a shell function as its first argument, running

      declare -n ref=$1

inside the function creates a nameref variable ref whose value is the variable name passed as the first argument. References and assignments to ref are treated as references and assignments to the variable whose name was passed as· $1. If the control variable in a for loop has the nameref attribute, the list of words can be a list of shell variables, and a name reference will be· established for each word in the list, in turn, when the loop is executed. Array variables cannot be given the -n attribute. However, nameref variables can reference array variables and subscripted array variables. Namerefs can be· unset using the -n option to the unset builtin. Otherwise, if unset is executed with the name of a nameref variable as an argument, the variable referenced by· the nameref variable will be unset.

For example (EDIT 2: (thank you Ron) namespaced (prefixed) the function-internal variable name, to minimize external variable clashes, which should finally answer properly, the issue raised in the comments by Karsten):

# $1 : string; your variable to contain the return value
function return_a_string () {
    declare -n ret=$1
    local MYLIB_return_a_string_message="The date is "
    MYLIB_return_a_string_message+=$(date)
    ret=$MYLIB_return_a_string_message
}

and testing this example:

$ return_a_string result; echo $result
The date is 20160817

Note that the bash "declare" builtin, when used in a function, makes the declared variable "local" by default, and "-n" can also be used with "local".

I prefer to distinguish "important declare" variables from "boring local" variables, so using "declare" and "local" in this way acts as documentation.

EDIT 1 - (Response to comment below by Karsten) - I cannot add comments below any more, but Karsten's comment got me thinking, so I did the following test which WORKS FINE, AFAICT - Karsten if you read this, please provide an exact set of test steps from the command line, showing the problem you assume exists, because these following steps work just fine:

$ return_a_string ret; echo $ret
The date is 20170104

(I ran this just now, after pasting the above function into a bash term - as you can see, the result works just fine.)

How can one display images side by side in a GitHub README.md?

This will display the three images side by side if the images are not too wide.

<p float="left">
  <img src="/img1.png" width="100" />
  <img src="/img2.png" width="100" /> 
  <img src="/img3.png" width="100" />
</p>

apc vs eaccelerator vs xcache

Even both eacceleator and xcache perform quite well during moderate loads, APC maintains its stability under serious request intensity. If we're talking about a few hundred requests/sec here, you'll not feel the difference. But if you're trying to respond more, definetely stick with APC. Especially if your application has overly dynamic characteristics which will likely cause locking issues under such loads. http://www.ipsure.com/blog/2011/eaccelerator-as-zend-extension-high-load-averages-issue/ may help.

TypeScript error TS1005: ';' expected (II)

On Windows you can have in your PATH 

PATH = ...;C:\Program Files (x86)\Microsoft SDKs\TypeScript\1.0\; ...

remove it from PATH env, then 

npm install -g typescript@latest

it worked for me to solve the

"TypeScript error TS1005: ';' expected"

See also how to update TypeScript to latest version with npm?

Select All as default value for Multivalue parameter

Using dataset with default values is one way, but you must use query for Available values and for Default Values, if values are hard coded in Available values tab, then you must define default values as expressions. Pictures should explain everything

Create Parameter (if not automaticly created)

Create Parameter

Define values - wrong way example

Define values - wrong way

Define values - correct way example

Define values - correct way

Set default values - you must define all default values reflecting available values to make "Select All" by default, if you won't define all only those defined will be selected by default.

Set default values

The Result

The result

One picture for Data type: Int

One picture for Data type Int

function to return a string in java

In Java, a String is a reference to heap-allocated storage. Returning "ans" only returns the reference so there is no need for stack-allocated storage. In fact, there is no way in Java to allocate objects in stack storage.

I would change to this, though. You don't need "ans" at all.

return String.format("%d:%d", mins, secs);

Hibernate Error executing DDL via JDBC Statement

spring.jpa.hibernate.ddl-auto = update

change update to create, and run it

after run safely again change create to update so again all tables will not create and you can use your previous data

Can HTML be embedded inside PHP "if" statement?

 
<?php if ($my_name == 'aboutme') { ?>
    HTML_GOES_HERE
<?php } ?>

Flutter: Setting the height of the AppBar

You can use the toolbarHeight property of Appbar, it does exactly what you want.

What's the use of ob_start() in php?

I use this so I can break out of PHP with a lot of HTML but not render it. It saves me from storing it as a string which disables IDE color-coding.

<?php
ob_start();
?>
<div>
    <span>text</span>
    <a href="#">link</a>
</div>
<?php
$content = ob_get_clean();
?>

Instead of:

<?php
$content = '<div>
    <span>text</span>
    <a href="#">link</a>
</div>';
?>

How to add anchor tags dynamically to a div in Javascript?

 
<script type="text/javascript" language="javascript">
function createDiv()
{
  var divTag = document.createElement("div");            
  divTag.innerHTML = "Div tag created using Javascript DOM dynamically";        
  document.body.appendChild(divTag);
}
</script>

Fastest way to zero out a 2d array in C?

Well, the fastest way to do it is to not do it at all.

Sounds odd I know, here's some pseudocode:

int array [][];
bool array_is_empty;


void ClearArray ()
{
   array_is_empty = true;
}

int ReadValue (int x, int y)
{
   return array_is_empty ? 0 : array [x][y];
}

void SetValue (int x, int y, int value)
{
   if (array_is_empty)
   {
      memset (array, 0, number of byte the array uses);
      array_is_empty = false;
   }
   array [x][y] = value;
}

Actually, it's still clearing the array, but only when something is being written to the array. This isn't a big advantage here. However, if the 2D array was implemented using, say, a quad tree (not a dynamic one mind), or a collection of rows of data, then you can localise the effect of the boolean flag, but you'd need more flags. In the quad tree just set the empty flag for the root node, in the array of rows just set the flag for each row.

Which leads to the question "why do you want to repeatedly zero a large 2d array"? What is the array used for? Is there a way to change the code so that the array doesn't need zeroing?

For example, if you had:

clear array
for each set of data
  for each element in data set
    array += element

that is, use it for an accumulation buffer, then changing it like this would improve the performance no end:

 for set 0 and set 1
   for each element in each set
     array = element1 + element2

 for remaining data sets
   for each element in data set
     array += element

This doesn't require the array to be cleared but still works. And that will be far faster than clearing the array. Like I said, the fastest way is to not do it in the first place.

Automatically creating directories with file output

The os.makedirs function does this. Try the following:

import os
import errno

filename = "/foo/bar/baz.txt"
if not os.path.exists(os.path.dirname(filename)):
    try:
        os.makedirs(os.path.dirname(filename))
    except OSError as exc: # Guard against race condition
        if exc.errno != errno.EEXIST:
            raise

with open(filename, "w") as f:
    f.write("FOOBAR")

The reason to add the try-except block is to handle the case when the directory was created between the os.path.exists and the os.makedirs calls, so that to protect us from race conditions.

In Python 3.2+, there is a more elegant way that avoids the race condition above:

import os

filename = "/foo/bar/baz.txt"
os.makedirs(os.path.dirname(filename), exist_ok=True)
with open(filename, "w") as f:
    f.write("FOOBAR")

intelliJ IDEA 13 error: please select Android SDK

File -> Invalidate Caches / Restart did the trick for me (which is always a good first try)

Selecting multiple columns in a Pandas dataframe

You can also use df.pop():

>>> df = pd.DataFrame([('falcon', 'bird',    389.0),
...                    ('parrot', 'bird',     24.0),
...                    ('lion',   'mammal',   80.5),
...                    ('monkey', 'mammal', np.nan)],
...                   columns=('name', 'class', 'max_speed'))
>>> df
     name   class  max_speed
0  falcon    bird      389.0
1  parrot    bird       24.0
2    lion  mammal       80.5
3  monkey  mammal

>>> df.pop('class')
0      bird
1      bird
2    mammal
3    mammal
Name: class, dtype: object

>>> df
     name  max_speed
0  falcon      389.0
1  parrot       24.0
2    lion       80.5
3  monkey        NaN

Please use df.pop(c).

Bold black cursor in Eclipse deletes code, and I don't know how to get rid of it

It sounds like you hit the "Insert" key .. in most applications this results in a fat (solid rectangle) cursor being displayed, as your screenshot suggests. This indicates that you are in overwrite mode rather than the default insert mode.

Just hit the "insert" key on your keyboard once more... it's usually near the 'delete' (not backspace), scroll lock and 'Print Screen' (often above the cursor keys in a full size keyboard.) This will switch back to insert mode and turn your cursor into a vertical line rather than a rectangle.

How to make IPython notebook matplotlib plot inline

I did the anaconda install but matplotlib is not plotting

It starts plotting when i did this

import matplotlib
import numpy as np
import matplotlib.pyplot as plt
%matplotlib inline

How to get the part of a file after the first line that matches a regular expression?

sed is a much better tool for the job: sed -n '/re/,$p' file

where re is regexp.

Another option is grep's --after-context flag. You need to pass in a number to end at, using wc on the file should give the right value to stop at. Combine this with -n and your match expression.

PHP cURL vs file_get_contents

In addition to this, due to some recent website hacks we had to secure our sites more. In doing so, we discovered that file_get_contents failed to work, where curl still would work.

Not 100%, but I believe that this php.ini setting may have been blocking the file_get_contents request.

; Disable allow_url_fopen for security reasons
allow_url_fopen = 0

Either way, our code now works with curl.

What does HTTP/1.1 302 mean exactly?

From RFC 2616 (the Hypertext Transfer Protocol Specification):

10.3.3 302 Found

   The requested resource resides temporarily under a different URI.
   Since the redirection might be altered on occasion, the client SHOULD
   continue to use the Request-URI for future requests.  This response
   is only cacheable if indicated by a Cache-Control or Expires header
   field.

   The temporary URI SHOULD be given by the Location field in the
   response. Unless the request method was HEAD, the entity of the
   response SHOULD contain a short hypertext note with a hyperlink to
   the new URI(s).

Source:

http://www.ietf.org/rfc/rfc2616.txt

CSS Styling for a Button: Using <input type="button> instead of <button>

In your .button CSS, try display:inline-block. See this JSFiddle

JUnit 5: How to assert an exception is thrown?

Actually I think there is a error in the documentation for this particular example. The method that is intended is expectThrows

public static void assertThrows(
public static <T extends Throwable> T expectThrows(

Can we have functions inside functions in C++?

You can't have local functions in C++. However, C++11 has lambdas. Lambdas are basically variables that work like functions.

A lambda has the type std::function (actually that's not quite true, but in most cases you can suppose it is). To use this type, you need to #include <functional>. std::function is a template, taking as template argument the return type and the argument types, with the syntax std::function<ReturnType(ArgumentTypes)>. For example, std::function<int(std::string, float)> is a lambda returning an int and taking two arguments, one std::string and one float. The most common one is std::function<void()>, which returns nothing and takes no arguments.

Once a lambda is declared, it is called just like a normal function, using the syntax lambda(arguments).

To define a lambda, use the syntax [captures](arguments){code} (there are other ways of doing it, but I won't mention them here). arguments is what arguments the lambda takes, and code is the code that should be run when the lambda is called. Usually you put [=] or [&] as captures. [=] means that you capture all variables in the scope in which the value is defined by value, which means that they will keep the value that they had when the lambda was declared. [&] means that you capture all variables in the scope by reference, which means that they will always have their current value, but if they are erased from memory the program will crash. Here are some examples:

#include <functional>
#include <iostream>

int main(){
    int x = 1;

    std::function<void()> lambda1 = [=](){
        std::cout << x << std::endl;
    };
    std::function<void()> lambda2 = [&](){
        std::cout << x << std::endl;
    };

    x = 2;
    lambda1();    //Prints 1 since that was the value of x when it was captured and x was captured by value with [=]
    lambda2();    //Prints 2 since that's the current value of x and x was captured by reference with [&]

    std::function<void()> lambda3 = [](){}, lambda4 = [](){};    //I prefer to initialize these since calling an uninitialized lambda is undefined behavior.
                                                                 //[](){} is the empty lambda.

    {
        int y = 3;    //y will be deleted from the memory at the end of this scope
        lambda3 = [=](){
            std::cout << y << endl;
        };
        lambda4 = [&](){
            std::cout << y << endl;
        };
    }

    lambda3();    //Prints 3, since that's the value y had when it was captured

    lambda4();    //Causes the program to crash, since y was captured by reference and y doesn't exist anymore.
                  //This is a bit like if you had a pointer to y which now points nowhere because y has been deleted from the memory.
                  //This is why you should be careful when capturing by reference.

    return 0;
}

You can also capture specific variables by specifying their names. Just specifying their name will capture them by value, specifying their name with a & before will capture them by reference. For example, [=, &foo] will capture all variables by value except foo which will be captured by reference, and [&, foo] will capture all variables by reference except foo which will be captured by value. You can also capture only specific variables, for example [&foo] will capture foo by reference and will capture no other variables. You can also capture no variables at all by using []. If you try to use a variable in a lambda that you didn't capture, it won't compile. Here is an example:

#include <functional>

int main(){
    int x = 4, y = 5;

    std::function<void(int)> myLambda = [y](int z){
        int xSquare = x * x;    //Compiler error because x wasn't captured
        int ySquare = y * y;    //OK because y was captured
        int zSquare = z * z;    //OK because z is an argument of the lambda
    };

    return 0;
}

You can't change the value of a variable that was captured by value inside a lambda (variables captured by value have a const type inside the lambda). To do so, you need to capture the variable by reference. Here is an exampmle:

#include <functional>

int main(){
    int x = 3, y = 5;
    std::function<void()> myLambda = [x, &y](){
        x = 2;    //Compiler error because x is captured by value and so it's of type const int inside the lambda
        y = 2;    //OK because y is captured by reference
    };
    x = 2;    //This is of course OK because we're not inside the lambda
    return 0;
}

Also, calling uninitialized lambdas is undefined behavior and will usually cause the program to crash. For example, never do this:

std::function<void()> lambda;
lambda();    //Undefined behavior because lambda is uninitialized

Examples

Here is the code for what you wanted to do in your question using lambdas:

#include <functional>    //Don't forget this, otherwise you won't be able to use the std::function type

int main(){
    std::function<void()> a = [](){
        // code
    }
    a();
    return 0;
}

Here is a more advanced example of a lambda:

#include <functional>    //For std::function
#include <iostream>      //For std::cout

int main(){
    int x = 4;
    std::function<float(int)> divideByX = [x](int y){
        return (float)y / (float)x;    //x is a captured variable, y is an argument
    }
    std::cout << divideByX(3) << std::endl;    //Prints 0.75
    return 0;
}

jQuery get the name of a select option

In your codethis refers to the select element not to the selected option

to refer the selected option you can do this -

$(this).find('option:selected').attr("name");

Required attribute on multiple checkboxes with the same name?

Here is improvement for icova's answer. It also groups inputs by name.

$(function(){
  var allRequiredCheckboxes = $(':checkbox[required]');
  var checkboxNames = [];

  for (var i = 0; i < allRequiredCheckboxes.length; ++i){
    var name = allRequiredCheckboxes[i].name;
    checkboxNames.push(name);
  }

  checkboxNames = checkboxNames.reduce(function(p, c) {
    if (p.indexOf(c) < 0) p.push(c);
    return p;
  }, []);

  for (var i in checkboxNames){
    !function(){
      var name = checkboxNames[i];
      var checkboxes = $('input[name="' + name + '"]');
      checkboxes.change(function(){
        if(checkboxes.is(':checked')) {
          checkboxes.removeAttr('required');
        } else {
          checkboxes.attr('required', 'required');
        }
      });
    }();
  }

});

How to access PHP variables in JavaScript or jQuery rather than <?php echo $variable ?>

I ran into a similar issue when building a custom pagination for a site I am working on.

The global variable I created in functions.php was defined and set to 0. I could output this value in my javascript no problem using the method @Karsten outlined above. The issue was with updating the global variable that I initially set to 0 inside the PHP file.

Here is my workaround (hacky? I know!) but after struggling for an hour on a tight deadline the following works:

Inside archive-episodes.php:

<script>
    // We define the variable and update it in a php
    // function defined in functions.php
    var totalPageCount; 
</script>

Inside functions.php

<?php
    $totalPageCount = WP_Query->max_num_pages; // In my testing scenario this number is 8.
    echo '<script>totalPageCount = $totalPageCount;</script>';
?>

To keep it simple, I was outputting the totalPageCount variable in an $ajax.success callback via alert.

$.ajax({
        url: ajaxurl,
        type: 'POST',
        data: {"action": "infinite_scroll", "page_no": pageNumber, "posts_per_page": numResults},
        beforeSend: function() {
            $(".ajaxLoading").show();
        },
        success: function(data) {
                            //alert("DONE LOADING EPISODES");
            $(".ajaxLoading").hide();

            var $container = $("#episode-container");

            if(firstRun) {
                $container.prepend(data);
                initMasonry($container);
                ieMasonryFix();
                initSearch();
            } else {
                var $newItems = $(data);
                $container.append( $newItems ).isotope( 'appended', $newItems );
            }
            firstRun = false;

            addHoverState();                            
            smartResize();

            alert(totalEpiPageCount); // THIS OUTPUTS THE CORRECT PAGE TOTAL
        }

Be it as it may, I hope this helps others! If anyone has a "less-hacky" version or best-practise example I'm all ears.

How to process images of a video, frame by frame, in video streaming using OpenCV and Python

According to the latest updates for OpenCV 3.0 and higher, you need to change the Property Identifiers as follows in the code by Mehran:

cv2.cv.CV_CAP_PROP_POS_FRAMES

to 

cv2.CAP_PROP_POS_FRAMES

and same applies to cv2.CAP_PROP_POS_FRAME_COUNT.

Hope it helps.

Passing Multiple route params in Angular2

OK realized a mistake .. it has to be /:id/:id2

Anyway didn't find this in any tutorial or other StackOverflow question.

@RouteConfig([{path: '/component/:id/:id2',name: 'MyCompB', component:MyCompB}])
export class MyCompA {
    onClick(){
        this._router.navigate( ['MyCompB', {id: "someId", id2: "another ID"}]);
    }
}

Is there a difference between PhoneGap and Cordova commands?

This first choice might be a confusing one but it’s really very simple. PhoneGap is a product owned by Adobe which currently includes additional build services, and it may or may not eventually offer additional services and/or charge payments for use in the future. Cordova is owned and maintained by Apache, and will always be maintained as an open source project. Currently they both have a very similar API. I would recommend going with Cordova, unless you require the additional PhoneGap build services.

Is it possible to change the speed of HTML's <marquee> tag?

_x000D_
_x000D_ 
<marquee behavior=scroll direction="left" scrollamount="5">Your message here</marquee>
_x000D_
_x000D_
_x000D_

scrollamount controls the speed of text: higher the value higher is the scrolling speed

MySQL Daemon Failed to Start - centos 6

I had the same issue happening. When I checked the error.log I found that my disk was full.

Use:

df -h

on the command line. it will tell you how much space you have left. mine was full. found my error.log file was 4.77GB. I downloaded it and then deleted it. Then I used service mysqld start and it worked.

AppStore - App status is ready for sale, but not in app store

You may also need to provide your contact info, bank info, and tax info in this page so it will allow your last release on App Store:

https://itunesconnect.apple.com/WebObjects/iTunesConnect.woa/wo/6.0

Where can I find error log files?

You can use "lsof" to find open logfiles on your system. lsof just gives you a list of all open files.

Use grep for "log" ... use grep again for "php" (if the filename contains the strings "log" and "php" like in "php_error_log" and you are root user you will find the files without knowing the configuration).

        root@lnx-work:~# lsof |grep log
        ... snip
        gmain     12148 12274       user   13r      REG              252,1    32768     661814 /home/user/.local/share/gvfs-metadata/home-11ab0393.log
        gmain     12148 12274       user   21r      REG              252,1    32768     662622 /home/user/.local/share/gvfs-metadata/root-56222fe2.log
        gvfs-udis 12246             user  mem       REG              252,1    55384     790567 /lib/x86_64-linux-gnu/libsystemd-login.so.0.7.1
==> apache 12333             user  mem       REG              252,1    55384     790367 /var/log/http/php_error_log**
        ... snip 


        root@lnx-work:~# lsof |grep log |grep php 
        **apache 12333             user  mem       REG              252,1    55384     790367 /var/log/http/php_error_log**
        ... snip

Also see this article on finding open logfiles: Find open logfiles on a linux system

How to set session timeout in web.config

Use this in web.config:

<sessionState 

  timeout="20" 
/>

Git asks for username every time I push

This occurs when one downloads using HTTPS rather than the SSH,easiet way which I implemented was I pushed everything as I made a few changes once wherein it asked for the username and password, then I removed the directory from my machine and git clone SSH address. It was solved.

Just clone it using SSH rather than HTTP and it won't ask for username or password.

Also having two-factor authentication creates the problem even when you download using SSH so disabling it solves the issue.

How to disable <br> tags inside <div> by css?

 
<p style="color:black">Shop our collection of beautiful women's <br> <span> wedding ring in classic &amp; modern design.</span></p>

Remove <br> effect using CSS.

<style> p br{ display:none; } </style>

how to convert java string to Date object

You basically effectively converted your date in a string format to a date object. If you print it out at that point, you will get the standard date formatting output. In order to format it after that, you then need to convert it back to a date object with a specified format (already specified previously)

String startDateString = "06/27/2007";
DateFormat df = new SimpleDateFormat("MM/dd/yyyy"); 
Date startDate;
try {
    startDate = df.parse(startDateString);
    String newDateString = df.format(startDate);
    System.out.println(newDateString);
} catch (ParseException e) {
    e.printStackTrace();
}

jQuery document.createElement equivalent?

What about this, for example when you want to add a <option> element inside a <select>

$('<option/>')
  .val(optionVal)
  .text('some option')
  .appendTo('#mySelect')

You can obviously apply to any element

$('<div/>')
  .css('border-color', red)
  .text('some text')
  .appendTo('#parentDiv')

How to obtain the number of CPUs/cores in Linux from the command line?

Not my web page, but this command from http://www.ixbrian.com/blog/?p=64&cm_mc_uid=89402252817914508279022&cm_mc_sid_50200000=1450827902 works nicely for me on centos. It will show actual cpus even when hyperthreading is enabled.

cat /proc/cpuinfo | egrep "core id|physical id" | tr -d "\n" | sed s/physical/\\nphysical/g | grep -v ^$ | sort | uniq | wc -l

Why do we usually use || over |? What is the difference?

| does not do short-circuit evaluation in boolean expressions. || will stop evaluating if the first operand is true, but | won't.

In addition, | can be used to perform the bitwise-OR operation on byte/short/int/long values. || cannot.

Force browser to refresh css, javascript, etc

I have decided that since browsers do not check for new versions of css and js files, I rename my css and js directories whenever I make a change. I use css1 to css9 and js1 to js9 as the directory names. When I get to 9, I next start over at 1. It is a pain, but it works perfectly every time. It is ridiculous to have to tell users to type .

Delimiters in MySQL

When you create a stored routine that has a BEGIN...END block, statements within the block are terminated by semicolon (;). But the CREATE PROCEDURE statement also needs a terminator. So it becomes ambiguous whether the semicolon within the body of the routine terminates CREATE PROCEDURE, or terminates one of the statements within the body of the procedure.

The way to resolve the ambiguity is to declare a distinct string (which must not occur within the body of the procedure) that the MySQL client recognizes as the true terminator for the CREATE PROCEDURE statement.

CSS scrollbar style cross browser

Webkit's support for scrollbars is quite sophisticated. This CSS gives a very minimal scrollbar, with a light grey track and a darker thumb:

::-webkit-scrollbar
{
  width: 12px;  /* for vertical scrollbars */
  height: 12px; /* for horizontal scrollbars */
}

::-webkit-scrollbar-track
{
  background: rgba(0, 0, 0, 0.1);
}

::-webkit-scrollbar-thumb
{
  background: rgba(0, 0, 0, 0.5);
}

This answer is a fantastic source of additional information.

How to implement a FSM - Finite State Machine in Java

Consider the easy, lightweight Java library EasyFlow. From their docs:

With EasyFlow you can:

  • implement complex logic but keep your code simple and clean
  • handle asynchronous calls with ease and elegance
  • avoid concurrency by using event-driven programming approach
  • avoid StackOverflow error by avoiding recursion
  • simplify design, programming and testing of complex java applications

How to use mouseover and mouseout in Angular 6

Adding to what was already said.

if you want to *ngFor an element , and hide \ show elements in it, on hover, like you added in the comments, you should re-think the whole concept.

a more appropriate way to do it, does not involve angular at all. I would go with pure CSS instead, using its native :hover property.

something like:

App.Component.css

div span.only-show-on-hover {
    visibility: hidden;
}
div:hover span.only-show-on-hover  {
    visibility: visible;
}

App.Component.html

  <div *ngFor="let i of [1,2,3,4]" > hover me please.
    <span class="only-show-on-hover">you only see me when hovering</span>
  </div>

added a demo: https://stackblitz.com/edit/hello-angular-6-hvgx7n?file=src%2Fapp%2Fapp.component.html

Split a python list into other "sublists" i.e smaller lists

 
chunks = [data[100*i:100*(i+1)] for i in range(len(data)/100 + 1)]

This is equivalent to the accepted answer. For example, shortening to batches of 10 for readability:

data = range(35)
print [data[x:x+10] for x in xrange(0, len(data), 10)]
print [data[10*i:10*(i+1)] for i in range(len(data)/10 + 1)]

Outputs:

[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30, 31, 32, 33, 34]]
[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [10, 11, 12, 13, 14, 15, 16, 17, 18, 19], [20, 21, 22, 23, 24, 25, 26, 27, 28, 29], [30, 31, 32, 33, 34]]

Faster way to zero memory than with memset?

memset is generally designed to be very very fast general-purpose setting/zeroing code. It handles all cases with different sizes and alignments, which affect the kinds of instructions you can use to do your work. Depending on what system you're on (and what vendor your stdlib comes from), the underlying implementation might be in assembler specific to that architecture to take advantage of whatever its native properties are. It might also have internal special cases to handle the case of zeroing (versus setting some other value).

That said, if you have very specific, very performance critical memory zeroing to do, it's certainly possible that you could beat a specific memset implementation by doing it yourself. memset and its friends in the standard library are always fun targets for one-upmanship programming. :)

How to Display Selected Item in Bootstrap Button Dropdown Title

Further modified based on answer from @Kyle as $.text() returns exact string, so the caret tag is printed literally, than as a markup, just in case someone would like to keep the caret intact in dropdown.

$(".dropdown-menu li").click(function(){
  $(this).parents(".btn-group").find('.btn').html(
  $(this).text()+" <span class=\"caret\"></span>"
  );
});

How to $watch multiple variable change in angular

 
$scope.$watch('age + name', function () {
  //called when name or age changed
});

No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here

after I add the property:

<prop key="hibernate.current_session_context_class">thread</prop> I get the exception like:

org.hibernate.HibernateException: createQuery is not valid without active transaction
org.hibernate.HibernateException: save is not valid without active transaction.

so I think setting that property is not a good solution.

finally I solve "No Hibernate Session bound to thread" problem :

1.<!-- <prop key="hibernate.current_session_context_class">thread</prop> -->
2.add <tx:annotation-driven /> to servlet-context.xml or dispatcher-servlet.xml
3.add @Transactional after @Service and @Repository

Get string between two strings in a string

If you are looking for a 1 line solution, this is it:

s.Substring(s.IndexOf("eT") + "eT".Length).Split("97".ToCharArray()).First()

The whole 1 line solution, with System.Linq:

using System;
using System.Linq;

class OneLiner
{
    static void Main()
    {
        string s = "TextHereTisImortant973End"; //Between "eT" and "97"
        Console.WriteLine(s.Substring(s.IndexOf("eT") + "eT".Length)
                           .Split("97".ToCharArray()).First());
    }
}

JPA Query selecting only specific columns without using Criteria Query?

Yes, like in plain sql you could specify what kind of properties you want to select:

SELECT i.firstProperty, i.secondProperty FROM ObjectName i WHERE i.id=10

Executing this query will return a list of Object[], where each array contains the selected properties of one object.

Another way is to wrap the selected properties in a custom object and execute it in a TypedQuery:

String query = "SELECT NEW CustomObject(i.firstProperty, i.secondProperty) FROM ObjectName i WHERE i.id=10";
TypedQuery<CustomObject> typedQuery = em.createQuery(query , CustomObject.class);
List<CustomObject> results = typedQuery.getResultList();

Examples can be found in this article.

UPDATE 29.03.2018:

@Krish:

@PatrickLeitermann for me its giving "Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: Unable to locate class ***" exception . how to solve this ?

I guess you’re using JPA in the context of a Spring application, don't you? Some other people had exactly the same problem and their solution was adding the fully qualified name (e. g. com.example.CustomObject) after the SELECT NEW keywords.

Maybe the internal implementation of the Spring data framework only recognizes classes annotated with @Entity or registered in a specific orm file by their simple name, which causes using this workaround.

Replace all non Alpha Numeric characters, New Lines, and multiple White Space with one Space

Jonny 5 beat me to it. I was going to suggest using the \W+ without the \s as in text.replace(/\W+/g, " "). This covers white space as well.

What is the difference between HTTP 1.1 and HTTP 2.0?

HTTP/2 supports queries multiplexing, headers compression, priority and more intelligent packet streaming management. This results in reduced latency and accelerates content download on modern web pages.

More details here.

Java time-based map/cache with expiring keys

This is a sample implementation that i did for the same requirement and concurrency works well. Might be useful for someone.

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 
 * @author Vivekananthan M
 *
 * @param <K>
 * @param <V>
 */
public class WeakConcurrentHashMap<K, V> extends ConcurrentHashMap<K, V> {

    private static final long serialVersionUID = 1L;

    private Map<K, Long> timeMap = new ConcurrentHashMap<K, Long>();
    private long expiryInMillis = 1000;
    private static final SimpleDateFormat sdf = new SimpleDateFormat("hh:mm:ss:SSS");

    public WeakConcurrentHashMap() {
        initialize();
    }

    public WeakConcurrentHashMap(long expiryInMillis) {
        this.expiryInMillis = expiryInMillis;
        initialize();
    }

    void initialize() {
        new CleanerThread().start();
    }

    @Override
    public V put(K key, V value) {
        Date date = new Date();
        timeMap.put(key, date.getTime());
        System.out.println("Inserting : " + sdf.format(date) + " : " + key + " : " + value);
        V returnVal = super.put(key, value);
        return returnVal;
    }

    @Override
    public void putAll(Map<? extends K, ? extends V> m) {
        for (K key : m.keySet()) {
            put(key, m.get(key));
        }
    }

    @Override
    public V putIfAbsent(K key, V value) {
        if (!containsKey(key))
            return put(key, value);
        else
            return get(key);
    }

    class CleanerThread extends Thread {
        @Override
        public void run() {
            System.out.println("Initiating Cleaner Thread..");
            while (true) {
                cleanMap();
                try {
                    Thread.sleep(expiryInMillis / 2);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        private void cleanMap() {
            long currentTime = new Date().getTime();
            for (K key : timeMap.keySet()) {
                if (currentTime > (timeMap.get(key) + expiryInMillis)) {
                    V value = remove(key);
                    timeMap.remove(key);
                    System.out.println("Removing : " + sdf.format(new Date()) + " : " + key + " : " + value);
                }
            }
        }
    }
}


Git Repo Link (With Listener Implementation)

https://github.com/vivekjustthink/WeakConcurrentHashMap

Cheers!!

Escaping regex string

Use the re.escape() function for this:

4.2.3 re Module Contents

escape(string)

Return string with all non-alphanumerics backslashed; this is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it.

A simplistic example, search any occurence of the provided string optionally followed by 's', and return the match object.

def simplistic_plural(word, text):
    word_or_plural = re.escape(word) + 's?'
    return re.match(word_or_plural, text)

Sending and Parsing JSON Objects in Android

GSON is easiest to use and the way to go if the data have a definite structure.

Download gson.

Add it to the referenced libraries.

package com.tut.JSON;

import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class SimpleJson extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        String jString = "{\"username\": \"tom\", \"message\": \"roger that\"}  ";


        GsonBuilder gsonb = new GsonBuilder();
        Gson gson = gsonb.create();
        Post pst;

        try {
            pst = gson.fromJson(jString,  Post.class);

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
}

Code for Post class

package com.tut.JSON;

public class Post {

    String message;
    String time;
    String username;
    Bitmap icon;
}

Converting HTML files to PDF

Did you try WKHTMLTOPDF?

It's a simple shell utility, an open source implementation of WebKit. Both are free.

We've set a small tutorial here

EDIT( 2017 ):

If it was to build something today, I wouldn't go that route anymore.
But would use http://pdfkit.org/ instead.
Probably stripping it of all its nodejs dependencies, to run in the browser.

Using unset vs. setting a variable to empty

So, by unset'ting the array index 2, you essentially remove that element in the array and decrement the array size (?).

I made my own test..

foo=(5 6 8)
echo ${#foo[*]}
unset foo
echo ${#foo[*]}

Which results in..

3
0

So just to clarify that unset'ting the entire array will in fact remove it entirely.

Python: How to convert datetime format?

 
>>> import datetime
>>> d = datetime.datetime.strptime('2011-06-09', '%Y-%m-%d')
>>> d.strftime('%b %d,%Y')
'Jun 09,2011'

In pre-2.5 Python, you can replace datetime.strptime with time.strptime, like so (untested): datetime.datetime(*(time.strptime('2011-06-09', '%Y-%m-%d')[0:6]))

How to get exit code when using Python subprocess communicate method?

This worked for me. It also prints the output returned by the child process

child = subprocess.Popen(serial_script_cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
    retValRunJobsSerialScript = 0
    for line in child.stdout.readlines():
        child.wait()
        print line           
    retValRunJobsSerialScript= child.returncode

Why is Spring's ApplicationContext.getBean considered bad?

Others have pointed to the general problem (and are valid answers), but I'll just offer one additional comment: it's not that you should NEVER do it, but rather that do it as little as possible.

Usually this means that it is done exactly once: during bootstrapping. And then it's just to access the "root" bean, through which other dependencies can be resolved. This can be reusable code, like base servlet (if developing web apps).

Why do 64-bit DLLs go to System32 and 32-bit DLLs to SysWoW64 on 64-bit Windows?

Other folks have already done a good job of explaining this ridiculus conundrum ... and I think Chris Hoffman did an even better job here: https://www.howtogeek.com/326509/whats-the-difference-between-the-system32-and-syswow64-folders-in-windows/

My two thoughts:

  1. We all make stupid short-sighted mistakes in life. When Microsoft named their (at the time) Win32 DLL directory "System32", it made sense at the time ... they just didn't take into consideration what would happen if/when a 64-bit (or 128-bit) version of their OS got developed later - and the massive backward compatibility issue such a directory name would cause. Hindsight is always 20-20, so I can't really blame them (too much) for such a mistake. ...HOWEVER... When Microsoft did later develop their 64-bit operating system, even with the benefit of hindsight, why oh why would they make not only the exact same short-sighted mistake AGAIN but make it even worse by PURPOSEFULLY giving it such a misleading name?!? Shame on them!!! Why not AT LEAST actually name the directory "SysWin32OnWin64" to avoid confusion?!? And what happens when they eventually produce a 128-bit OS ... then where are they going to put their 32-bit, 64-bit, and 128-bit DLLs?!?

  2. All of this logic still seems completely flawed to me. On 32-bit versions of Windows, System32 contains 32-bit DLLs; on 64-bit versions of Windows, System32 contains 64-bit DLLs ... so that developers wouldn't have to make code changes, correct? The problem with this logic is that those developers are either now making 64-bit apps needing 64-bit DLLs or they're making 32-bit apps needing 32-bit DLLs ... either way, aren't they still screwed? I mean, if they're still making a 32-bit app, for it to now run on a 64-bit Windows, they'll now need to make a code change to find/reference the same ol' 32-bit DLL they used before (now located in SysWOW64). Or, if they're working on a 64-bit app, they're going to need to re-write their old app for the new OS anyway ... so a recompile/rebuild was going to be needed anyway!!!

Microsoft just hurts me sometimes.

Java: method to get position of a match in a String?

I have some big code but working nicely....

   class strDemo
   { 
       public static void main(String args[])
       {
       String s1=new String("The Ghost of The Arabean Sea");
           String s2=new String ("The");
           String s6=new String ("ehT");
           StringBuffer s3;
           StringBuffer s4=new StringBuffer(s1);
           StringBuffer s5=new StringBuffer(s2);
           char c1[]=new char[30];
           char c2[]=new char[5];
           char c3[]=new char[5];
           s1.getChars(0,28,c1,0);
           s2.getChars(0,3,c2,0);
           s6.getChars(0,3,c3,0); s3=s4.reverse();      
           int pf=0,pl=0;
           char c5[]=new char[30];
           s3.getChars(0,28,c5,0);
           for(int i=0;i<(s1.length()-s2.length());i++)
           {
               int j=0;
               if(pf<=1)
               {
                  while (c1[i+j]==c2[j] && j<=s2.length())
                  {           
                    j++;
                    System.out.println(s2.length()+" "+j);
                    if(j>=s2.length())
                    {
                       System.out.println("first match of(The) :->"+i);

                     }
                     pf=pf+1;         
                  }   
             }                
       }       
         for(int i=0;i<(s3.length()-s6.length()+1);i++)
        {
            int j=0;
            if(pl<=1)
            {
             while (c5[i+j]==c3[j] && j<=s6.length())
             {
                 j++;
                 System.out.println(s6.length()+" "+j);
                 if(j>=s6.length())
                 {
                         System.out.println((s3.length()-i-3));
                         pl=pl+1;

                 }   
                }                 
              }  
           }  
         }
       }

Write lines of text to a file in R

In newer versions of R, writeLines will preserve returns and spaces in your text, so you don't need to include \n at the end of lines and you can write one big chunk of text to a file. This will work with the example,

txt <- "Hello
World"
fileConn<-file("output.txt")
writeLines(txt, fileConn)
close(fileConn)

But you could also use this setup to simply include text with structure (linebreaks or indents)

txt <- "Hello
   world
 I can 
   indent text!"
fileConn<-file("output.txt")
writeLines(txt, fileConn)
close(fileConn)

Checking if output of a command contains a certain string in a shell script

Test the return value of grep:

./somecommand | grep 'string' &> /dev/null
if [ $? == 0 ]; then
   echo "matched"
fi

which is done idiomatically like so:

if ./somecommand | grep -q 'string'; then
   echo "matched"
fi

and also:

./somecommand | grep -q 'string' && echo 'matched'

jQuery $.ajax(), pass success data into separate function

Works fine for me:

<script src="/jquery.js"></script>
<script>
var callback = function(data, textStatus, xhr)
{
    alert(data + "\t" + textStatus);
}

var test = function(str, cb) {
    var data = 'Input values';
    $.ajax({
        type: 'post',
        url: 'http://www.mydomain.com/ajaxscript',
        data: data,
        success: cb
    });
}
test('Hello, world', callback);
</script>

Modify SVG fill color when being served as Background-Image

I needed something similar and wanted to stick with CSS. Here are LESS and SCSS mixins as well as plain CSS that can help you with this. Unfortunately, it's browser support is a bit lax. See below for details on browser support.

LESS mixin:

.element-color(@color) {
  background-image: url('data:image/svg+xml;utf8,<svg ...><g stroke="@{color}" ... /></g></svg>');
}

LESS usage:

.element-color(#fff);

SCSS mixin:

@mixin element-color($color) {
  background-image: url('data:image/svg+xml;utf8,<svg ...><g stroke="#{$color}" ... /></g></svg>');
}

SCSS usage:

@include element-color(#fff);

CSS:

// color: red
background-image: url('data:image/svg+xml;utf8,<svg ...><g stroke="red" ... /></g></svg>');

Here is more info on embedding the full SVG code into your CSS file. It also mentioned browser compatibility which is a bit too small for this to be a viable option.

Placing a textview on top of imageview in android

Try this:

<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/rel_layout"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<ImageView
    android:id="@+id/ImageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src=//source of image />

<TextView
    android:id="@+id/ImageViewText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@id/ImageView"
    android:layout_alignTop="@id/ImageView"
    android:layout_alignRight="@id/ImageView"
    android:layout_alignBottom="@id/ImageView"
    android:text=//u r text here
    android:gravity="center"
    />

Hope this could help you.

How to call one shell script from another shell script?

 
pathToShell="/home/praveen/"   
chmod a+x $pathToShell"myShell.sh"
sh $pathToShell"myShell.sh"

How to Call VBA Function from Excel Cells?

The issue you have encountered is that UDFs cannot modify the Excel environment, they can only return a value to the calling cell.

There are several alternatives

  1. For the sample given you don't actually need VBA. This formula will work
    ='C:\Users\UserName\Desktop\[TestSample.xlsx]Sheet1'!$B$2

  2. Use a rather messy work around: See this answer

  3. You can use ExecuteExcel4Macro or OLEDB

Configure Flask dev server to be visible across the network

I had the same problem, I use PyCharm as an editor and when I created the project, PyCharm created a Flask Server. What I did was create a server with Python in the following way;

Config Python Server PyCharm basically what I did was create a new server but flask if not python

I hope it helps you

How to disable a ts rule for a specific line?

@ts-expect-error

TS 3.9 introduces a new magic comment. @ts-expect-error will:

  • have same functionality as @ts-ignore
  • trigger an error, if actually no compiler error has been suppressed (= indicates useless flag)
if (false) {
  // @ts-expect-error: Let's ignore a single compiler error like this unreachable code 
  console.log("hello"); // compiles
}

// If @ts-expect-error didn't suppress anything at all, we now get a nice warning 
let flag = true;
// ...
if (flag) {
  // @ts-expect-error
  // ^~~~~~~~~~~~~~~^ error: "Unused '@ts-expect-error' directive.(2578)"
  console.log("hello"); 
}

Alternatives

@ts-ignore and @ts-expect-error can be used for all sorts of compiler errors. For type issues (like in OP), I recommend one of the following alternatives due to narrower error suppression scope:

? Use any type

// type assertion for single expression
delete ($ as any).summernote.options.keyMap.pc.TAB;

// new variable assignment for multiple usages
const $$: any = $
delete $$.summernote.options.keyMap.pc.TAB;
delete $$.summernote.options.keyMap.mac.TAB;

? Augment JQueryStatic interface

// ./global.d.ts
interface JQueryStatic {
  summernote: any;
}

// ./main.ts
delete $.summernote.options.keyMap.pc.TAB; // works

In other cases, shorthand module declarations or module augmentations for modules with no/extendable types are handy utilities. A viable strategy is also to keep not migrated code in .js and use --allowJs with checkJs: false.

How to find the sum of an array of numbers

Recommended (reduce with default value)

Array.prototype.reduce can be used to iterate through the array, adding the current element value to the sum of the previous element values.

_x000D_
_x000D_ 
console.log(_x000D_
  [1, 2, 3, 4].reduce((a, b) => a + b, 0)_x000D_
)_x000D_
console.log(_x000D_
  [].reduce((a, b) => a + b, 0)_x000D_
)
_x000D_
_x000D_
_x000D_

Without default value

You get a TypeError

_x000D_
_x000D_ 
console.log(_x000D_
  [].reduce((a, b) => a + b)_x000D_
)
_x000D_
_x000D_
_x000D_

Prior to ES6's arrow functions

_x000D_
_x000D_ 
console.log(_x000D_
  [1,2,3].reduce(function(acc, val) { return acc + val; }, 0)_x000D_
)_x000D_
_x000D_
console.log(_x000D_
  [].reduce(function(acc, val) { return acc + val; }, 0)_x000D_
)
_x000D_
_x000D_
_x000D_

Non-number inputs

If non-numbers are possible inputs, you may want to handle that?

_x000D_
_x000D_ 
console.log(_x000D_
  ["hi", 1, 2, "frog"].reduce((a, b) => a + b)_x000D_
)_x000D_
_x000D_
let numOr0 = n => isNaN(n) ? 0 : n_x000D_
_x000D_
console.log(_x000D_
  ["hi", 1, 2, "frog"].reduce((a, b) => _x000D_
    numOr0(a) + numOr0(b))_x000D_
)
_x000D_
_x000D_
_x000D_

Non-recommended dangerous eval use

We can use eval to execute a string representation of JavaScript code. Using the Array.prototype.join function to convert the array to a string, we change [1,2,3] into "1+2+3", which evaluates to 6.

_x000D_
_x000D_ 
console.log(_x000D_
  eval([1,2,3].join('+'))_x000D_
)_x000D_
_x000D_
//This way is dangerous if the array is built_x000D_
// from user input as it may be exploited eg: _x000D_
_x000D_
eval([1,"2;alert('Malicious code!')"].join('+'))
_x000D_
_x000D_
_x000D_

Of course displaying an alert isn't the worst thing that could happen. The only reason I have included this is as an answer Ortund's question as I do not think it was clarified.

How to style an asp.net menu with CSS

There are well achieved third-party tools, but i usually use superfish http://www.conceptdevelopment.net/Fun/Superfish/ it's cool, free and easy ;)

Getting around the Max String size in a vba function?

This works and shows more than 255 characters in the message box.

Sub TestStrLength()
    Dim s As String
    Dim i As Integer

    s = ""
    For i = 1 To 500
        s = s & "1234567890"
    Next i

    MsgBox s
End Sub

The message box truncates the string to 1023 characters, but the string itself can be very large.

I would also recommend that instead of using fixed variables names with numbers (e.g. Var1, Var2, Var3, ... Var255) that you use an array. This is much shorter declaration and easier to use - loops.

Here's an example:

Sub StrArray()
Dim var(256) As Integer
Dim i As Integer
Dim s As String

For i = 1 To 256
    var(i) = i
Next i

s = "Tims_pet_Robot"
For i = 1 To 256
    s = s & " """ & var(i) & """"
Next i

    SecondSub (s)
End Sub

Sub SecondSub(s As String)
    MsgBox "String length = " & Len(s)
End Sub

Updated this to show that a string can be longer than 255 characters and used in a subroutine/function as a parameter that way. This shows that the string length is 1443 characters. The actual limit in VBA is 2GB per string.

Perhaps there is instead a problem with the API that you are using and that has a limit to the string (such as a fixed length string). The issue is not with VBA itself.

Ok, I see the problem is specifically with the Application.OnTime method itself. It is behaving like Excel functions in that they only accept strings that are up to 255 characters in length. VBA procedures and functions though do not have this limit as I have shown. Perhaps then this limit is imposed for any built-in Excel object method.

Update:
changed ...longer than 256 characters... to ...longer than 255 characters...

What is Dispatcher Servlet in Spring?

We can say like DispatcherServlet taking care of everything in Spring MVC.

At web container start up:

  1. DispatcherServlet will be loaded and initialized by calling init() method
  2. init() of DispatcherServlet will try to identify the Spring Configuration Document with naming conventions like "servlet_name-servlet.xml" then all beans can be identified.

Example:

public class DispatcherServlet extends HttpServlet {

    ApplicationContext ctx = null;

    public void init(ServletConfig cfg){
        // 1. try to get the spring configuration document with default naming conventions
        String xml = "servlet_name" + "-servlet.xml";

        //if it was found then creates the ApplicationContext object
        ctx = new XmlWebApplicationContext(xml);
    }
    ...
}

So, in generally DispatcherServlet capture request URI and hand over to HandlerMapping. HandlerMapping search mapping bean with method of controller, where controller returning logical name(view). Then this logical name is send to DispatcherServlet by HandlerMapping. Then DispatcherServlet tell ViewResolver to give full location of view by appending prefix and suffix, then DispatcherServlet give view to the client.

How to grep with a list of words

You need to use the option -f:

$ grep -f A B

The option -F does a fixed string search where as -f is for specifying a file of patterns. You may want both if the file only contains fixed strings and not regexps.

$ grep -Ff A B

You may also want the -w option for matching whole words only:

$ grep -wFf A B

Read man grep for a description of all the possible arguments and what they do.

How to move from one fragment to another fragment on click of an ImageView in Android?

When you are inside an activity and need to go to a fragment use below

getFragmentManager().beginTransaction().replace(R.id.*TO_BE_REPLACED_LAYOUT_ID*, new tasks()).commit();

But when you are inside a fragment and need to go to a fragment then just add a getActivity(). before, so it would become

getActivity().getFragmentManager().beginTransaction().replace(R.id.*TO_BE_REPLACED_LAYOUT_ID*, new tasks()).commit();

as simple as that.

The *TO_BE_REPLACED_LAYOUT_ID* can be the entire page of activity or a part of it, just make sure to put an id to the layout to be replaced. It is general practice to put the replaceable layout in a FrameLayout .

How can I convert spaces to tabs in Vim or Linux?

Linux: with unexpand (and expand)

Here is a very good solution: https://stackoverflow.com/a/11094620/1115187, mostly because it uses *nix-utilities:

  1. unexpand — spaces -> tabs
  2. expand — tabs -> spaces

Linux: custom script

My original answer

Bash snippet for replacing 4-spaces indentation (there are two {4} in script) with tabs in all .py files in the ./app folder (recursively):

find ./app -iname '*.py' -type f \
    -exec awk -i inplace \
    '{ match($0, /^(( {4})*)(.*?)$/, arr); gsub(/ {4}/, "\t", arr[1]) }; { print arr[1] arr[3] }' {} \;

It doesn't modify 4-spaces in the middle or at the end.

Was tested under Ubuntu 16.0x and Linux Mint 18

How do I change the ID of a HTML element with JavaScript?

That seems to work for me:

<html>
<head><style>
#monkey {color:blue}
#ape {color:purple}
</style></head>
<body>
<span id="monkey" onclick="changeid()">
fruit
</span>
<script>
function changeid ()
{
var e = document.getElementById("monkey");
e.id = "ape";
}
</script>
</body>
</html>

The expected behaviour is to change the colour of the word "fruit".

Perhaps your document was not fully loaded when you called the routine?

Even though JRE 8 is installed on my MAC -" No Java Runtime present,requesting to install " gets displayed in terminal

If you came across the error when tried to generate a jks file (keystore), so try adding 

/Applications/Android\ Studio.app/Contents/jre/jdk/Contents/Home/bin/keytool

before running the command, like so:

/Applications/Android\ Studio.app/Contents/jre/jdk/Contents/Home/bin/keytool -genkey -v -keystore ~/key.jks -keyalg RSA -keysize 2048 -validity 10000 -alias key

Django CharField vs TextField

For eg.,. 2 fields are added in a model like below..

description = models.TextField(blank=True, null=True)
title = models.CharField(max_length=64, blank=True, null=True)

Below are the mysql queries executed when migrations are applied.

for TextField(description) the field is defined as a longtext

ALTER TABLE `sometable_sometable` ADD COLUMN `description` longtext NULL;

The maximum length of TextField of MySQL is 4GB according to string-type-overview.

for CharField(title) the max_length(required) is defined as varchar(64)

ALTER TABLE `sometable_sometable` ADD COLUMN `title` varchar(64) NULL;
ALTER TABLE `sometable_sometable` ALTER COLUMN `title` DROP DEFAULT;

Drawing a dot on HTML5 canvas

If you are planning to draw a lot of pixel, it's a lot more efficient to use the image data of the canvas to do pixel drawing.

var canvas = document.getElementById("myCanvas");
var canvasWidth = canvas.width;
var canvasHeight = canvas.height;
var ctx = canvas.getContext("2d");
var canvasData = ctx.getImageData(0, 0, canvasWidth, canvasHeight);

// That's how you define the value of a pixel //
function drawPixel (x, y, r, g, b, a) {
    var index = (x + y * canvasWidth) * 4;

    canvasData.data[index + 0] = r;
    canvasData.data[index + 1] = g;
    canvasData.data[index + 2] = b;
    canvasData.data[index + 3] = a;
}

// That's how you update the canvas, so that your //
// modification are taken in consideration //
function updateCanvas() {
    ctx.putImageData(canvasData, 0, 0);
}

Then, you can use it in this way :

drawPixel(1, 1, 255, 0, 0, 255);
drawPixel(1, 2, 255, 0, 0, 255);
drawPixel(1, 3, 255, 0, 0, 255);
updateCanvas();

For more information, you can take a look at this Mozilla blog post : http://hacks.mozilla.org/2009/06/pushing-pixels-with-canvas/

How to set shadows in React Native for android?

I have implemented CardView for react-native with elevation, that support android(All version) and iOS. Let me know is it help you or not. https://github.com/Kishanjvaghela/react-native-cardview

import CardView from 'react-native-cardview'
<CardView
          cardElevation={2}
          cardMaxElevation={2}
          cornerRadius={5}>
          <Text>
              Elevation 0
          </Text>
</CardView>

enter image description here

How do I set path while saving a cookie value in JavaScript?

For access cookie in whole app (use path=/):

function createCookie(name,value,days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime()+(days*24*60*60*1000));
        var expires = "; expires="+date.toGMTString();
    }
    else var expires = "";
    document.cookie = name+"="+value+expires+"; path=/"; 
}

Note:

If you set path=/,
Now the cookie is available for whole application/domain. If you not specify the path then current cookie is save just for the current page you can't access it on another page(s).

For more info read- http://www.quirksmode.org/js/cookies.html (Domain and path part)

If you use cookies in jquery by plugin jquery-cookie:

$.cookie('name', 'value', { expires: 7, path: '/' });
//or
$.cookie('name', 'value', { path: '/' });

Reverse / invert a dictionary mapping

This handles non-unique values and retains much of the look of the unique case. 

inv_map = {v:[k for k in my_map if my_map[k] == v] for v in my_map.itervalues()}

For Python 3.x, replace itervalues with values.

How to properly highlight selected item on RecyclerView?

Make selector:

 <?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@color/Green_10" android:state_activated="true" />
    <item android:drawable="@color/Transparent" />
</selector>

Set it as background at your list item layout

   <?xml version="1.0" encoding="utf-8"?>
    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:background="@drawable/selector_attentions_list_item"
        android:layout_width="match_parent"
        android:layout_height="64dp">

In your adapter add OnClickListener to the view (onBind method)

 @Suppress("UNCHECKED_CAST")
    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        fun bindItems(item: T) {
            initItemView(itemView, item)
            itemView.tag = item
            if (isClickable) {
                itemView.setOnClickListener(onClickListener)
            }
        }
    }

In the onClick event activate the view:

 fun onItemClicked(view: View){
        view.isActivated = true
    }

How to select date without time in SQL

If you want to return a date type as just a date use

CONVERT(date, SYSDATETIME())

or 

SELECT CONVERT(date,SYSDATETIME())

or

DECLARE @DateOnly Datetime
SET @DateOnly=CONVERT(date,SYSDATETIME())

Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve
  1. Try "File"->"Invalidate Caches / Restart ..."
  2. Try to clean up your .gradle and .idea directory under your project root directory.

  3. Try to add Google Maven repository and sync project

    buildscript {
    repositories {
        jcenter()
        google()
        maven {
           url "https://maven.google.com"
        }
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
    }
}

allprojects {
    repositories {
        google()
        jcenter()
        maven {
           url "https://maven.google.com"
        }
    }
}

  4. If you are using Android Gradle Plugin 3.1.3, you should be sure that your gradle wrapper version is 4.4. Under the root directory of your project, find gradle-wrapper.properties and modify it as below.

    distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip

How to set text size in a button in html

Without using inline CSS you could set the text size of all your buttons using:

input[type="submit"], input[type="button"] {
  font-size: 14px;
}

How to read HDF5 files in Python

To read the content of .hdf5 file as an array, you can do something as follow

> import numpy as np 
> myarray = np.fromfile('file.hdf5', dtype=float)
> print(myarray)

python pandas dataframe columns convert to dict key and value

If lakes is your DataFrame, you can do something like

area_dict = dict(zip(lakes.area, lakes.count))

How can I set the 'backend' in matplotlib in Python?

For new comers,

matplotlib.pyplot.switch_backend(newbackend)

Formatting doubles for output in C#

Take a look at this MSDN reference. In the notes it states that the numbers are rounded to the number of decimal places requested.

If instead you use "{0:R}" it will produce what's referred to as a "round-trip" value, take a look at this MSDN reference for more info, here's my code and the output:

double d = 10 * 0.69;
Console.WriteLine("  {0:R}", d);
Console.WriteLine("+ {0:F20}", 6.9 - d);
Console.WriteLine("= {0:F20}", 6.9);

output

  6.8999999999999995
+ 0.00000000000000088818
= 6.90000000000000000000

How do I append a node to an existing XML file in java

You can parse the existing XML file into DOM and append new elements to the DOM. Very similar to what you did with creating brand new XML. I am assuming you do not have to worry about duplicate server. If you do have to worry about that, you will have to go through the elements in the DOM to check for duplicates.

DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();

/* parse existing file to DOM */
Document document = documentBuilder.parse(new File("exisgint/xml/file"));

Element root = document.getDocumentElement();

for (Server newServer : Collection<Server> bunchOfNewServers){
  Element server = Document.createElement("server");
  /* create and setup the server node...*/

 root.appendChild(server);
}

/* use whatever method to output DOM to XML (for example, using transformer like you did).*/

Understanding passport serialize deserialize

For anyone using Koa and koa-passport:

Know that the key for the user set in the serializeUser method (often a unique id for that user) will be stored in:

this.session.passport.user

When you set in done(null, user) in deserializeUser where 'user' is some user object from your database:

this.req.user OR this.passport.user

for some reason this.user Koa context never gets set when you call done(null, user) in your deserializeUser method.

So you can write your own middleware after the call to app.use(passport.session()) to put it in this.user like so:

app.use(function * setUserInContext (next) {
  this.user = this.req.user
  yield next
})

If you're unclear on how serializeUser and deserializeUser work, just hit me up on twitter. @yvanscher

LINQ to SQL - Left Outer Join with multiple join conditions

I know it's "a bit late" but just in case if anybody needs to do this in LINQ Method syntax (which is why I found this post initially), this would be how to do that:

var results = context.Periods
    .GroupJoin(
        context.Facts,
        period => period.id,
        fk => fk.periodid,
        (period, fact) => fact.Where(f => f.otherid == 17)
                              .Select(fact.Value)
                              .DefaultIfEmpty()
    )
    .Where(period.companyid==100)
    .SelectMany(fact=>fact).ToList();

How to automatically add user account AND password with a Bash script?

From IBM (https://www.ibm.com/support/knowledgecenter/ssw_aix_61/com.ibm.aix.cmds1/chpasswd.htm):

Create a text file, say text.txt and populate it with user:password pairs as follows:

user1:password1
user2:password2
...
usern:passwordn

Save the text.txt file, and run

cat text.txt | chpassword

That's it. The solution is (a) scalable and (b) does not involve printing passwords on the command line.

Occurrences of substring in a string

The answer given as correct is no good for counting things like line returns and is far too verbose. Later answers are better but all can be achieved simply with

str.split(findStr).length

It does not drop trailing matches using the example in the question.

npm install doesn't create node_modules directory

See @Cesco's answer: npm init is really all you need

I was having the same issue - running npm install somePackage was not generating a node_modules dir.

I created a package.json file at the root, which contained a simple JSON obj:

{
    "name": "please-work"
}

On the next npm install the node_modules directory appeared.

How can I change my default database in SQL Server without using MS SQL Server Management Studio?

To do it the GUI way, you need to go edit your login. One of its properties is the default database used for that login. You can find the list of logins under the Logins node under the Security node. Then select your login and right-click and pick Properties. Change the default database and your life will be better!

Note that someone with sysadmin privs needs to be able to login to do this or to run the query from the previous post.

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

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

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

Try instead with:

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

What is the best way to initialize a JavaScript Date to midnight?

In case you already have d3.js as a dependency in your project, or don't mind bringing it in, d3-time (d3.js library is modular as of v4.0.0) has got Intervals.

They might prove useful when setting dates to "default" values, e.g. midnight, 0.00 seconds, the first of the month, etc. 

var d = new Date(); // Wed Aug 02 2017 15:01:07 GMT+0200 (CEST)
d3.timeHour(d) // Wed Aug 02 2017 00:00:00 GMT+0200 (CEST)
d3.timeMonth(d) // Tue Aug 01 2017 00:00:00 GMT+0200 (CEST)

Create a batch file to run an .exe with an additional parameter

in batch file abc.bat

cd c:\user\ben_dchost\documents\
executible.exe -flag1 -flag2 -flag3

I am assuming that your executible.exe is present in c:\user\ben_dchost\documents\ I am also assuming that the parameters it takes are -flag1 -flag2 -flag3

Edited:

For the command you say you want to execute, do:

cd C:\Users\Ben\Desktop\BGInfo\
bginfo.exe dc_bginfo.bgi
pause

Hope this helps

How to navigate through textfields (Next / Done Buttons)

I am surprised by how many answers here fail to understand one simple concept: navigating through controls in your app is not something the views themselves should do. It's the controller's job to decide which control to make the next first responder.

Also most answers only applied to navigating forward, but users may also want to go backwards.

So here's what I've come up with. Your form should be managed by a view controller, and view controllers are part of the responder chain. So you're perfectly free to implement the following methods:

#pragma mark - Key Commands

- (NSArray *)keyCommands
{
    static NSArray *commands;

    static dispatch_once_t once;
    dispatch_once(&once, ^{
        UIKeyCommand *const forward = [UIKeyCommand keyCommandWithInput:@"\t" modifierFlags:0 action:@selector(tabForward:)];
        UIKeyCommand *const backward = [UIKeyCommand keyCommandWithInput:@"\t" modifierFlags:UIKeyModifierShift action:@selector(tabBackward:)];

        commands = @[forward, backward];
    });

    return commands;
}

- (void)tabForward:(UIKeyCommand *)command
{
    NSArray *const controls = self.controls;
    UIResponder *firstResponder = nil;

    for (UIResponder *const responder in controls) {
        if (firstResponder != nil && responder.canBecomeFirstResponder) {
            [responder becomeFirstResponder]; return;
        }
        else if (responder.isFirstResponder) {
            firstResponder = responder;
        }
    }

    [controls.firstObject becomeFirstResponder];
}

- (void)tabBackward:(UIKeyCommand *)command
{
    NSArray *const controls = self.controls;
    UIResponder *firstResponder = nil;

    for (UIResponder *const responder in controls.reverseObjectEnumerator) {
        if (firstResponder != nil && responder.canBecomeFirstResponder) {
            [responder becomeFirstResponder]; return;
        }
        else if (responder.isFirstResponder) {
            firstResponder = responder;
        }
    }

    [controls.lastObject becomeFirstResponder];
}

Additional logic for scrolling offscreen responders visible beforehand may apply.

Another advantage of this approach is that you don't need to subclass all kinds of controls you may want to display (like UITextFields) but can instead manage the logic at controller level, where, let's be honest, is the right place to do so.

What does "select count(1) from table_name" on any database tables mean?

 
SELECT COUNT(1) from <table name>

should do the exact same thing as 

SELECT COUNT(*)  from <table name>

There may have been or still be some reasons why it would perform better than SELECT COUNT(*)on some database, but I would consider that a bug in the DB.

SELECT COUNT(col_name) from <table name>

however has a different meaning, as it counts only the rows with a non-null value for the given column.

python 3.x ImportError: No module named 'cStringIO'

From Python 3.0 changelog;

The StringIO and cStringIO modules are gone. Instead, import the io module and use io.StringIO or io.BytesIO for text and data respectively.

From the Python 3 email documentation it can be seen that io.StringIO should be used instead:

from io import StringIO
from email.generator import Generator
fp = StringIO()
g = Generator(fp, mangle_from_=True, maxheaderlen=60)
g.flatten(msg)
text = fp.getvalue()

Reference: https://docs.python.org/3/library/io.html

How do I use arrays in C++?

Programmers often confuse multidimensional arrays with arrays of pointers.

Multidimensional arrays

Most programmers are familiar with named multidimensional arrays, but many are unaware of the fact that multidimensional array can also be created anonymously. Multidimensional arrays are often referred to as "arrays of arrays" or "true multidimensional arrays".

Named multidimensional arrays

When using named multidimensional arrays, all dimensions must be known at compile time:

int H = read_int();
int W = read_int();

int connect_four[6][7];   // okay

int connect_four[H][7];   // ISO C++ forbids variable length array
int connect_four[6][W];   // ISO C++ forbids variable length array
int connect_four[H][W];   // ISO C++ forbids variable length array

This is how a named multidimensional array looks like in memory:

              +---+---+---+---+---+---+---+
connect_four: |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+
              |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+
              |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+
              |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+
              |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+
              |   |   |   |   |   |   |   |
              +---+---+---+---+---+---+---+

Note that 2D grids such as the above are merely helpful visualizations. From the point of view of C++, memory is a "flat" sequence of bytes. The elements of a multidimensional array are stored in row-major order. That is, connect_four[0][6] and connect_four[1][0] are neighbors in memory. In fact, connect_four[0][7] and connect_four[1][0] denote the same element! This means that you can take multi-dimensional arrays and treat them as large, one-dimensional arrays:

int* p = &connect_four[0][0];
int* q = p + 42;
some_int_sequence_algorithm(p, q);

Anonymous multidimensional arrays

With anonymous multidimensional arrays, all dimensions except the first must be known at compile time:

int (*p)[7] = new int[6][7];   // okay
int (*p)[7] = new int[H][7];   // okay

int (*p)[W] = new int[6][W];   // ISO C++ forbids variable length array
int (*p)[W] = new int[H][W];   // ISO C++ forbids variable length array

This is how an anonymous multidimensional array looks like in memory:

              +---+---+---+---+---+---+---+
        +---> |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |     |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |     |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |     |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |     |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |     |   |   |   |   |   |   |   |
        |     +---+---+---+---+---+---+---+
        |
      +-|-+
   p: | | |
      +---+

Note that the array itself is still allocated as a single block in memory.

Arrays of pointers

You can overcome the restriction of fixed width by introducing another level of indirection.

Named arrays of pointers

Here is a named array of five pointers which are initialized with anonymous arrays of different lengths:

int* triangle[5];
for (int i = 0; i < 5; ++i)
{
    triangle[i] = new int[5 - i];
}

// ...

for (int i = 0; i < 5; ++i)
{
    delete[] triangle[i];
}

And here is how it looks like in memory:

          +---+---+---+---+---+
          |   |   |   |   |   |
          +---+---+---+---+---+
            ^
            | +---+---+---+---+
            | |   |   |   |   |
            | +---+---+---+---+
            |   ^
            |   | +---+---+---+
            |   | |   |   |   |
            |   | +---+---+---+
            |   |   ^
            |   |   | +---+---+
            |   |   | |   |   |
            |   |   | +---+---+
            |   |   |   ^
            |   |   |   | +---+
            |   |   |   | |   |
            |   |   |   | +---+
            |   |   |   |   ^
            |   |   |   |   |
            |   |   |   |   |
          +-|-+-|-+-|-+-|-+-|-+
triangle: | | | | | | | | | | |
          +---+---+---+---+---+

Since each line is allocated individually now, viewing 2D arrays as 1D arrays does not work anymore.

Anonymous arrays of pointers

Here is an anonymous array of 5 (or any other number of) pointers which are initialized with anonymous arrays of different lengths:

int n = calculate_five();   // or any other number
int** p = new int*[n];
for (int i = 0; i < n; ++i)
{
    p[i] = new int[n - i];
}

// ...

for (int i = 0; i < n; ++i)
{
    delete[] p[i];
}
delete[] p;   // note the extra delete[] !

And here is how it looks like in memory:

          +---+---+---+---+---+
          |   |   |   |   |   |
          +---+---+---+---+---+
            ^
            | +---+---+---+---+
            | |   |   |   |   |
            | +---+---+---+---+
            |   ^
            |   | +---+---+---+
            |   | |   |   |   |
            |   | +---+---+---+
            |   |   ^
            |   |   | +---+---+
            |   |   | |   |   |
            |   |   | +---+---+
            |   |   |   ^
            |   |   |   | +---+
            |   |   |   | |   |
            |   |   |   | +---+
            |   |   |   |   ^
            |   |   |   |   |
            |   |   |   |   |
          +-|-+-|-+-|-+-|-+-|-+
          | | | | | | | | | | |
          +---+---+---+---+---+
            ^
            |
            |
          +-|-+
       p: | | |
          +---+

Conversions

Array-to-pointer decay naturally extends to arrays of arrays and arrays of pointers:

int array_of_arrays[6][7];
int (*pointer_to_array)[7] = array_of_arrays;

int* array_of_pointers[6];
int** pointer_to_pointer = array_of_pointers;

However, there is no implicit conversion from T[h][w] to T**. If such an implicit conversion did exist, the result would be a pointer to the first element of an array of h pointers to T (each pointing to the first element of a line in the original 2D array), but that pointer array does not exist anywhere in memory yet. If you want such a conversion, you must create and fill the required pointer array manually:

int connect_four[6][7];

int** p = new int*[6];
for (int i = 0; i < 6; ++i)
{
    p[i] = connect_four[i];
}

// ...

delete[] p;

Note that this generates a view of the original multidimensional array. If you need a copy instead, you must create extra arrays and copy the data yourself:

int connect_four[6][7];

int** p = new int*[6];
for (int i = 0; i < 6; ++i)
{
    p[i] = new int[7];
    std::copy(connect_four[i], connect_four[i + 1], p[i]);
}

// ...

for (int i = 0; i < 6; ++i)
{
    delete[] p[i];
}
delete[] p;

How do I clear the std::queue efficiently?

Using a unique_ptr might be OK.
You then reset it to obtain an empty queue and release the memory of the first queue. As to the complexity? I'm not sure - but guess it's O(1).

Possible code:

typedef queue<int> quint;

unique_ptr<quint> p(new quint);

// ...

p.reset(new quint);  // the old queue has been destroyed and you start afresh with an empty queue

Hide all warnings in ipython

The accepted answer does not work in Jupyter (at least when using some libraries).

The Javascript solutions here only hide warnings that are already showing but not warnings that would be shown in the future.

To hide/unhide warnings in Jupyter and JupyterLab I wrote the following script that essentially toggles css to hide/unhide warnings.

%%javascript
(function(on) {
const e=$( "<a>Setup failed</a>" );
const ns="js_jupyter_suppress_warnings";
var cssrules=$("#"+ns);
if(!cssrules.length) cssrules = $("<style id='"+ns+"' type='text/css'>div.output_stderr { } </style>").appendTo("head");
e.click(function() {
    var s='Showing';  
    cssrules.empty()
    if(on) {
        s='Hiding';
        cssrules.append("div.output_stderr, div[data-mime-type*='.stderr'] { display:none; }");
    }
    e.text(s+' warnings (click to toggle)');
    on=!on;
}).click();
$(element).append(e);
})(true);

How to Get JSON Array Within JSON Object?

 
  Gson gson = new Gson();
                Type listType = new TypeToken<List<Data>>() {}.getType();
                List<Data>     cartProductList = gson.fromJson(response.body().get("data"), listType);
                Toast.makeText(getContext(), ""+cartProductList.get(0).getCity(), Toast.LENGTH_SHORT).show();

How to get current time and date in Android

Try This

String mytime = (DateFormat.format("dd-MM-yyyy hh:mm:ss", new java.util.Date()).toString());

How to send email attachments?

Here's another:

import smtplib
from os.path import basename
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.utils import COMMASPACE, formatdate


def send_mail(send_from, send_to, subject, text, files=None,
              server="127.0.0.1"):
    assert isinstance(send_to, list)

    msg = MIMEMultipart()
    msg['From'] = send_from
    msg['To'] = COMMASPACE.join(send_to)
    msg['Date'] = formatdate(localtime=True)
    msg['Subject'] = subject

    msg.attach(MIMEText(text))

    for f in files or []:
        with open(f, "rb") as fil:
            part = MIMEApplication(
                fil.read(),
                Name=basename(f)
            )
        # After the file is closed
        part['Content-Disposition'] = 'attachment; filename="%s"' % basename(f)
        msg.attach(part)


    smtp = smtplib.SMTP(server)
    smtp.sendmail(send_from, send_to, msg.as_string())
    smtp.close()

It's much the same as the first example... But it should be easier to drop in.

Loading custom configuration files

the articles posted by Ricky are very good, but unfortunately they don't answer your question.

To solve your problem you should try this piece of code:

ExeConfigurationFileMap configMap = new ExeConfigurationFileMap();
configMap.ExeConfigFilename = @"d:\test\justAConfigFile.config.whateverYouLikeExtension";
Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configMap, ConfigurationUserLevel.None);

If need to access a value within the config you can use the index operator:

config.AppSettings.Settings["test"].Value;

Understanding inplace=True

The inplace parameter:

df.dropna(axis='index', how='all', inplace=True)

in Pandas and in general means:

1. Pandas creates a copy of the original data

2. ... does some computation on it

3. ... assigns the results to the original data.

4. ... deletes the copy.

As you can read in the rest of my answer's further below, we still can have good reason to use this parameter i.e. the inplace operations, but we should avoid it if we can, as it generate more issues, as:

1. Your code will be harder to debug (Actually SettingwithCopyWarning stands for warning you to this possible problem)

2. Conflict with method chaining


So there is even case when we should use it yet?

Definitely yes. If we use pandas or any tool for handeling huge dataset, we can easily face the situation, where some big data can consume our entire memory. To avoid this unwanted effect we can use some technics like method chaining:

(
    wine.rename(columns={"color_intensity": "ci"})
    .assign(color_filter=lambda x: np.where((x.hue > 1) & (x.ci > 7), 1, 0))
    .query("alcohol > 14 and color_filter == 1")
    .sort_values("alcohol", ascending=False)
    .reset_index(drop=True)
    .loc[:, ["alcohol", "ci", "hue"]]
)

which make our code more compact (though harder to interpret and debug too) and consumes less memory as the chained methods works with the other method's returned values, thus resulting in only one copy of the input data. We can see clearly, that we will have 2 x original data memory consumption after this operations.

Or we can use inplace parameter (though harder to interpret and debug too) our memory consumption will be 2 x original data, but our memory consumption after this operation remains 1 x original data, which if somebody whenever worked with huge datasets exactly knows can be a big benefit.


Final conclusion:

Avoid using inplace parameter unless you don't work with huge data and be aware of its possible issues in case of still using of it.

How can I get the height and width of an uiimage?

 
UIImage *img = [UIImage imageNamed:@"logo.png"];

CGFloat width = img.size.width;
CGFloat height = img.size.height;

When is it appropriate to use C# partial classes?

If you have a sufficiently large class that doesn't lend itself to effective refactoring, separating it into multiple files helps keep things organized.

For instance, if you have a database for a site containing a discussion forum and a products system, and you don't want to create two different providers classes (NOT the same thing as a proxy class, just to be clear), you can create a single partial class in different files, like

MyProvider.cs - core logic

MyProvider.Forum.cs - methods pertaining specifically to the forum

MyProvider.Product.cs - methods for products

It's just another way to keep things organized.

Also, as others have said, it's about the only way to add methods to a generated class without running the risk of having your additions destroyed the next time the class is regenerated. This comes in handy with template-generated (T4) code, ORMs, etc.

How to declare an array of strings in C++?

You can directly declare an array of strings like string s[100];. Then if you want to access specific elements, you can get it directly like s[2][90]. For iteration purposes, take the size of string using the s[i].size() function.

Start thread with member function

Some users have already given their answer and explained it very well.

I would like to add few more things related to thread.

  1. How to work with functor and thread. Please refer to below example.

  2. The thread will make its own copy of the object while passing the object.

    #include<thread>
#include<Windows.h>
#include<iostream>

using namespace std;

class CB
{

public:
    CB()
    {
        cout << "this=" << this << endl;
    }
    void operator()();
};

void CB::operator()()
{
    cout << "this=" << this << endl;
    for (int i = 0; i < 5; i++)
    {
        cout << "CB()=" << i << endl;
        Sleep(1000);
    }
}

void main()
{
    CB obj;     // please note the address of obj.

    thread t(obj); // here obj will be passed by value 
                   //i.e. thread will make it own local copy of it.
                    // we can confirm it by matching the address of
                    //object printed in the constructor
                    // and address of the obj printed in the function

    t.join();
}

Another way of achieving the same thing is like:

void main()
{
    thread t((CB()));

    t.join();
}

But if you want to pass the object by reference then use the below syntax:

void main()
{
    CB obj;
    //thread t(obj);
    thread t(std::ref(obj));
    t.join();
}

Find object in list that has attribute equal to some value (that meets any condition)

You could also implement rich comparison via __eq__ method for your Test class and use in operator. Not sure if this is the best stand-alone way, but in case if you need to compare Test instances based on value somewhere else, this could be useful.

class Test:
    def __init__(self, value):
        self.value = value

    def __eq__(self, other):
        """To implement 'in' operator"""
        # Comparing with int (assuming "value" is int)
        if isinstance(other, int):
            return self.value == other
        # Comparing with another Test object
        elif isinstance(other, Test):
            return self.value == other.value

import random

value = 5

test_list = [Test(random.randint(0,100)) for x in range(1000)]

if value in test_list:
    print "i found it"

Dynamically Fill Jenkins Choice Parameter With Git Branches In a Specified Repo

expanding on @malenkiy_scot's answer. I created a new jenkins job to build up the file that is used by Extended Choice Plugin.

you can do the following (I did it as execute shell steps in jenkins, but you could do it in a script):

git ls-remote [email protected]:my/repo.git |grep refs/heads/* >tmp.txt
sed -e 's/.*refs\/heads\///' tmp.txt > tmp2.txt
tr '\n' ',' < tmp2.txt > tmp3.txt
sed '1i\branches=' tmp3.txt > tmp4.txt
tr -d '\n'  < tmp4.txt > branches.txt

I then use the Artifact deployer plugin to push that file to a shared location, which is in a web url, then just use 'http://localhost/branches.txt' in the Extended Choice plugin as the url. works like a charm.

ERROR! MySQL manager or server PID file could not be found! QNAP

Note: If you just want to stop MySQL server, this might be helpful. In my case, it kept on restarting as soon as I killed the process using PID. Also brew stop command didn't work as I installed without using homebrew. Then I went to mac system preferences and we have MySQL installed there. Just open it and stop the MySQL server and you're done. Here in the screenshot, you can find MySQL in bottom of system preferences.enter image description here

Cannot connect to Database server (mysql workbench)

Did you try to determine if this is a problem with Workbench or a general connection problem? Try this:

  1. Open a terminal
  2. Type mysql -u root -p -h 127.0.0.1 -P 3306
  3. If you can connect successfully you will see a mysql prompt after you type your password (type quit and Enter there to exit).

Report back how this worked.

How to convert Windows end of line in Unix end of line (CR/LF to LF)

Actually, vim does allow what you're looking for. Enter vim, and type the following commands: 

:args **/*.java
:argdo set ff=unix | update | next

The first of these commands sets the argument list to every file matching **/*.java, which is all Java files, recursively. The second of these commands does the following to each file in the argument list, in turn:

  • Sets the line-endings to Unix style (you already know this)
  • Writes the file out iff it's been changed
  • Proceeds to the next file

Is it possible to import modules from all files in a directory, using a wildcard?

If you are using webpack. This imports files automatically and exports as api namespace.

So no need to update on every file addition. 

import camelCase from "lodash-es";
const requireModule = require.context("./", false, /\.js$/); // 
const api = {};

requireModule.keys().forEach(fileName => {
  if (fileName === "./index.js") return;
  const moduleName = camelCase(fileName.replace(/(\.\/|\.js)/g, ""));
  api[moduleName] = {
    ...requireModule(fileName).default
  };
});

export default api;

For Typescript users;

import { camelCase } from "lodash-es"
const requireModule = require.context("./folderName", false, /\.ts$/)

interface LooseObject {
  [key: string]: any
}

const api: LooseObject = {}

requireModule.keys().forEach(fileName => {
  if (fileName === "./index.ts") return
  const moduleName = camelCase(fileName.replace(/(\.\/|\.ts)/g, ""))
  api[moduleName] = {
    ...requireModule(fileName).default,
  }
})

export default api

How to save an image locally using Python whose URL address I already know?

Use a simple python wget module to download the link. Usage below:

import wget
wget.download('http://www.digimouth.com/news/media/2011/09/google-logo.jpg')

How to put img inline with text

Images have display: inline by default.
You might want to put the image inside the paragraph.
<p><img /></p>

How can I create a dropdown menu from a List in Tkinter?

To create a "drop down menu" you can use OptionMenu in tkinter

Example of a basic OptionMenu:

from Tkinter import *

master = Tk()

variable = StringVar(master)
variable.set("one") # default value

w = OptionMenu(master, variable, "one", "two", "three")
w.pack()

mainloop()

More information (including the script above) can be found here.

Creating an OptionMenu of the months from a list would be as simple as:

from tkinter import *

OPTIONS = [
"Jan",
"Feb",
"Mar"
] #etc

master = Tk()

variable = StringVar(master)
variable.set(OPTIONS[0]) # default value

w = OptionMenu(master, variable, *OPTIONS)
w.pack()

mainloop()

In order to retrieve the value the user has selected you can simply use a .get() on the variable that we assigned to the widget, in the below case this is variable:

from tkinter import *

OPTIONS = [
"Jan",
"Feb",
"Mar"
] #etc

master = Tk()

variable = StringVar(master)
variable.set(OPTIONS[0]) # default value

w = OptionMenu(master, variable, *OPTIONS)
w.pack()

def ok():
    print ("value is:" + variable.get())

button = Button(master, text="OK", command=ok)
button.pack()

mainloop()

I would highly recommend reading through this site for further basic tkinter information as the above examples are modified from that site.

What's the best way to dedupe a table?

Deduping is rarely simple. That's because the records to be dedupped often have slightly different values is some of the fields. Therefore choose which record to keep can be problematic. Further, dups are often people records and it is hard to identify if the two John Smith's are two people or one person who is duplicated. So spend a lot (50% or more of the whole project) of your time defining what constitutes a dup and how to handle the differences and child records.

How do you know which is the correct value? Further dedupping requires that you handle all child records not orphaning any. What happens when you find that by changing the id on the child record you are suddenly violating one of the unique indexes or constraints - this will happen eventually and your process needs to handle it. If you have chosen foolishly to apply all your constraints only thorough the application, you may not even know the constraints are violated. When you have 10,000 records to dedup, you aren't going to go through the application to dedup one at a time. If the constraint isn't in the database, lots of luck in maintaining data integrity when you dedup.

A further complication is that dups don't always match exactly on the name or address. For instance a salesrep named Joan Martin may be a dup of a sales rep names Joan Martin-Jones especially if they have the same address and email. OR you could have John or Johnny in the name. Or the same street address except one record abbreveiated ST. and one spelled out Street. In SQL server you can use SSIS and fuzzy grouping to also identify near matches. These are often the most common dups as the fact that weren't exact matches is why they got put in as dups in the first place.

For some types of dedupping, you may need a user interface, so that the person doing the dedupping can choose which of two values to use for a particular field. This is especially true if the person who is being dedupped is in two or more roles. It could be that the data for a particular role is usually better than the data for another role. Or it could be that only the users will know for sure which is the correct value or they may need to contact people to find out if they are genuinely dups or simply two people with the same name.

Question mark characters displaying within text, why is this?

I got here looking for a solution for JavaScript displayed in the browser and although not directly related with a database...

In my case I copied and pasted some text I found on the internet into a JavaScript file and saved it with Windows Notepad.

When the page that uses that JavaScript file output the strings there were question marks (like the ones shown in the question) instead of the special characters like accented letters, etc.

I opened the file using Notepad++. Right after opening the file I saw that the character encoding was set as ANSI as you can see (mouse cursor on footer) in the following screenshot:

enter image description here

To solve the issue, click the Encoding menu in Notepad++ and select Encode in UTF-8. You should be good to go. :)

Password masking console application

Here is my simple version. Every time you hit a key, delete all from console and draw as many '*' as the length of password string is.

int chr = 0;
string pass = "";
const int ENTER = 13;
const int BS = 8;

do
{
   chr = Console.ReadKey().KeyChar;
   Console.Clear(); //imediately clear the char you printed

   //if the char is not 'return' or 'backspace' add it to pass string
   if (chr != ENTER && chr != BS) pass += (char)chr;

   //if you hit backspace remove last char from pass string
   if (chr == BS) pass = pass.Remove(pass.Length-1, 1);

   for (int i = 0; i < pass.Length; i++)
   {
      Console.Write('*');
   }
} 
 while (chr != ENTER);

Console.Write("\n");
Console.Write(pass);

Console.Read(); //just to see the pass

How to use a jQuery plugin inside Vue

You need to use either the globals loader or expose loader to ensure that webpack includes the jQuery lib in your source code output and so that it doesn't throw errors when your use $ in your components.

// example with expose loader:
npm i --save-dev expose-loader

// somewhere, import (require) this jquery, but pipe it through the expose loader
require('expose?$!expose?jQuery!jquery')

If you prefer, you can import (require) it directly within your webpack config as a point of entry, so I understand, but I don't have an example of this to hand

Alternatively, you can use the globals loader like this: https://www.npmjs.com/package/globals-loader

How to call a Python function from Node.js

Easiest way I know of is to use "child_process" package which comes packaged with node.

Then you can do something like:

const spawn = require("child_process").spawn;
const pythonProcess = spawn('python',["path/to/script.py", arg1, arg2, ...]);

Then all you have to do is make sure that you import sys in your python script, and then you can access arg1 using sys.argv[1], arg2 using sys.argv[2], and so on.

To send data back to node just do the following in the python script:

print(dataToSendBack)
sys.stdout.flush()

And then node can listen for data using:

pythonProcess.stdout.on('data', (data) => {
    // Do something with the data returned from python script
});

Since this allows multiple arguments to be passed to a script using spawn, you can restructure a python script so that one of the arguments decides which function to call, and the other argument gets passed to that function, etc.

Hope this was clear. Let me know if something needs clarification.

How do I create a MongoDB dump of my database?

This command will make a dump of given database in json and bson format.

mongodump -d <database name> -o <target directory>

How to add form validation pattern in Angular 2?

Since version 2.0.0-beta.8 (2016-03-02), Angular now includes a Validators.pattern regex validator.

See the CHANGELOG

How do you make a HTTP request with C++?

Note that this does not require libcurl, Windows.h, or WinSock! No compilation of libraries, no project configuration, etc. I have this code working in Visual Studio 2017 c++ on Windows 10:

#pragma comment(lib, "urlmon.lib")

#include <urlmon.h>
#include <sstream>

using namespace std;

...

IStream* stream;
//Also works with https URL's - unsure about the extent of SSL support though.
HRESULT result = URLOpenBlockingStream(0, "http://google.com", &stream, 0, 0);
if (result != 0)
{
    return 1;
}
char buffer[100];
unsigned long bytesRead;
stringstream ss;
stream->Read(buffer, 100, &bytesRead);
while (bytesRead > 0U)
{
    ss.write(buffer, (long long)bytesRead);
    stream->Read(buffer, 100, &bytesRead);
}
stream.Release();
string resultString = ss.str();

I just figured out how to do this, as I wanted a simple API access script, libraries like libcurl were causing me all kinds of problems (even when I followed the directions...), and WinSock is just too low-level and complicated.

I'm not quite sure about all of the IStream reading code (particularly the while condition - feel free to correct/improve), but hey, it works, hassle free! (It makes sense to me that, since I used a blocking (synchronous) call, this is fine, that bytesRead would always be > 0U until the stream (ISequentialStream?) is finished being read, but who knows.)

See also: URL Monikers and Asynchronous Pluggable Protocol Reference

"webxml attribute is required" error in Maven

Make sure to run mvn install before you compile your war.

Pandas DataFrame to List of Lists

Maybe something changed but this gave back a list of ndarrays which did what I needed.

list(df.values)

Httpd returning 503 Service Unavailable with mod_proxy for Tomcat 8

On CentOS Linux release 7.5.1804, we were able to make this work by editing /etc/selinux/config and changing the setting of SELINUX like so:

SELINUX=disabled

Excel VBA - read cell value from code

I think you need this ..

Dim n as Integer   

For n = 5 to 17
  msgbox cells(n,3) '--> sched waste
  msgbox cells(n,4) '--> type of treatm
  msgbox format(cells(n,5),"dd/MM/yyyy") '--> Lic exp
  msgbox cells(n,6) '--> email col
Next

Spring MVC - Why not able to use @RequestBody and @RequestParam together

It's too late to answer this question, but it could help for new readers, It seems version issues. I ran all these tests with spring 4.1.4 and found that the order of @RequestBody and @RequestParam doesn't matter.

  1. same as your result
  2. same as your result
  3. gave body= "name=abc", and name = "abc"
  4. Same as 3.
  5. body ="name=abc", name = "xyz,abc"
  6. same as 5.

Log exception with traceback

Uncaught exception messages go to STDERR, so instead of implementing your logging in Python itself you could send STDERR to a file using whatever shell you're using to run your Python script. In a Bash script, you can do this with output redirection, as described in the BASH guide.

Examples

Append errors to file, other output to the terminal:

./test.py 2>> mylog.log

Overwrite file with interleaved STDOUT and STDERR output:

./test.py &> mylog.log

How to set a default entity property value with Hibernate

i'am working with hibernate 5 and postgres, and this worked form me. 

@Column(name = "ACCOUNT_TYPE", ***nullable***=false, columnDefinition="varchar2 default 'END_USER'")
@Enumerated(EnumType.STRING)
private AccountType accountType;

g++ ld: symbol(s) not found for architecture x86_64

I had a similar warning/error/failure when I was simply trying to make an executable from two different object files (main.o and add.o). I was using the command:

gcc -o exec main.o add.o

But my program is a C++ program. Using the g++ compiler solved my issue:

g++ -o exec main.o add.o

I was always under the impression that gcc could figure these things out on its own. Apparently not. I hope this helps someone else searching for this error.

What is the command to exit a Console application in C#?

You can use Environment.Exit(0); and Application.Exit

Environment.Exit(0) is cleaner.

Get a particular cell value from HTML table using JavaScript

To get the text from this cell- 

<table>
    <tr id="somerow">
        <td>some text</td>            
    </tr>
</table>

You can use this - 

var Row = document.getElementById("somerow");
var Cells = Row.getElementsByTagName("td");
alert(Cells[0].innerText);

How to use Git for Unity3D source control?

You can use Github for Unity, a Unity Extension that brings the git workflow into the UI of Unity.

Github for Unity just released version 1.0 of the extension.

PHP: How to remove all non printable characters in a string?

you can use character classes

/[[:cntrl:]]+/

Dump all tables in CSV format using 'mysqldump'

This worked well for me:

mysqldump <DBNAME> --fields-terminated-by ',' \
--fields-enclosed-by '"' --fields-escaped-by '\' \
--no-create-info --tab /var/lib/mysql-files/

Or if you want to only dump a specific table:

mysqldump <DBNAME> <TABLENAME> --fields-terminated-by ',' \
--fields-enclosed-by '"' --fields-escaped-by '\' \
--no-create-info --tab /var/lib/mysql-files/

I'm dumping to /var/lib/mysql-files/ to avoid this error:

mysqldump: Got error: 1290: The MySQL server is running with the --secure-file-priv option so it cannot execute this statement when executing 'SELECT INTO OUTFILE'

How do I set up HttpContent for my HttpClient PostAsync second parameter?

To add to Preston's answer, here's the complete list of the HttpContent derived classes available in the standard library:

Credit: https://pfelix.wordpress.com/2012/01/16/the-new-system-net-http-classes-message-content/

Credit: https://pfelix.wordpress.com/2012/01/16/the-new-system-net-http-classes-message-content/

There's also a supposed ObjectContent but I was unable to find it in ASP.NET Core.

Of course, you could skip the whole HttpContent thing all together with Microsoft.AspNet.WebApi.Client extensions (you'll have to do an import to get it to work in ASP.NET Core for now: https://github.com/aspnet/Home/issues/1558) and then you can do things like:

var response = await client.PostAsJsonAsync("AddNewArticle", new Article
{
    Title = "New Article Title",
    Body = "New Article Body"
});

Align Div at bottom on main Div

I guess you'll need absolute position

.vertical_banner {position:relative;}
#bottom_link{position:absolute; bottom:0;}

Getting Git to work with a proxy server - fails with "Request timed out"

This worked for me, in windows XP behind a corporate firewall.

I didnt have to install any local proxy or any other software besides git v1.771 from http://code.google.com/p/msysgit/downloads/list?can=3

$ git config --global http.proxy http://proxyuser:[email protected]:8080
$ git config --system http.sslcainfo /bin/curl-ca-bundle.crt
$ git remote add origin https://mygithubuser:[email protected]/repoUser/repoName.git
$ git push origin master

proxyuser= the proxy user I was assigned by our IT dept, in my case it is the same windows user I use to log in to my PC, the Active Directory user

proxypwd= the password of my proxy user

proxy.server.com:8080 = the proxy name and port, I got it from Control Panel, Internet Options, Connections, Lan Settings button, Advanced button inside the Proxy Server section, use the servername and port on the first (http) row.

mygithubuser = the user I use to log in to github.com

mygithubpwd = the password for my github.com user

repoUser = the user owner of the repo

repoName = the name of the repo

How can I decrease the size of Ratingbar?

Check my answer here. Best way to achieve it. 

 <style name="MyRatingBar" parent="@android:style/Widget.RatingBar">
   <item name="android:minHeight">15dp</item>
   <item name="android:maxHeight">15dp</item>
   <item name="colorControlNormal">@color/white</item>
   <item name="colorControlActivated">@color/home_add</item>
</style>

and use like 

<RatingBar
    style="?android:attr/ratingBarStyleIndicator"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:isIndicator="false"
      android:max="5"
      android:rating="3"
      android:scaleX=".8"
      android:scaleY=".8"
      android:theme="@style/MyRatingBar" />

Rounding a variable to two decimal places C#

Make sure you provide a number, typically a double is used. Math.Round can take 1-3 arguments, the first argument is the variable you wish to round, the second is the number of decimal places and the third is the type of rounding.

double pay = 200 + bonus;
double pay = Math.Round(pay);
// Rounds to nearest even number, rounding 0.5 will round "down" to zero because zero is even
double pay = Math.Round(pay, 2, MidpointRounding.ToEven);
// Rounds up to nearest number
double pay = Math.Round(pay, 2, MidpointRounding.AwayFromZero);

Evaluate if list is empty JSTL

empty is an operator:

The empty operator is a prefix operation that can be used to determine whether a value is null or empty.

<c:if test="${empty myObject.featuresList}">

What does Java option -Xmx stand for?

 
C:\java -X

    -Xmixed           mixed mode execution (default)
    -Xint             interpreted mode execution only
    -Xbootclasspath:<directories and zip/jar files separated by ;>
                      set search path for bootstrap classes and resources
    -Xbootclasspath/a:<directories and zip/jar files separated by ;>
                      append to end of bootstrap class path
    -Xbootclasspath/p:<directories and zip/jar files separated by ;>
                      prepend in front of bootstrap class path
    -Xnoclassgc       disable class garbage collection
    -Xincgc           enable incremental garbage collection
    -Xloggc:<file>    log GC status to a file with time stamps
    -Xbatch           disable background compilation
    -Xms<size>        set initial Java heap size
    -Xmx<size>        set maximum Java heap size
    -Xss<size>        set java thread stack size
    -Xprof            output cpu profiling data
    -Xfuture          enable strictest checks, anticipating future default
    -Xrs              reduce use of OS signals by Java/VM (see documentation)
    -Xcheck:jni       perform additional checks for JNI functions
    -Xshare:off       do not attempt to use shared class data
    -Xshare:auto      use shared class data if possible (default)
    -Xshare:on        require using shared class data, otherwise fail.

The -X options are non-standard and subject to change without notice.

how to set imageview src?

Each image has a resource-number, which is an integer. Pass this number to "setImageResource" and you should be ok.

Check this link for further information:
http://developer.android.com/guide/topics/resources/accessing-resources.html

e.g.:

imageView.setImageResource(R.drawable.myimage);

"Automatic" vs "Automatic (Delayed start)"

In short, services set to Automatic will start during the boot process, while services set to start as Delayed will start shortly after boot.

Starting your service Delayed improves the boot performance of your server and has security benefits which are outlined in the article Adriano linked to in the comments.

Update: "shortly after boot" is actually 2 minutes after the last "automatic" service has started, by default. This can be configured by a registry key, according to Windows Internals and other sources (3,4).

The registry keys of interest (At least in some versions of windows) are:

  • HKLM\SYSTEM\CurrentControlSet\services\<service name>\DelayedAutostart will have the value 1 if delayed, 0 if not.
  • HKLM\SYSTEM\CurrentControlSet\services\AutoStartDelay or HKLM\SYSTEM\CurrentControlSet\Control\AutoStartDelay (on Windows 10): decimal number of seconds to wait, may need to create this one. Applies globally to all Delayed services.

What is Python used for?

Python is a dynamic, strongly typed, object oriented, multipurpose programming language, designed to be quick (to learn, to use, and to understand), and to enforce a clean and uniform syntax.

  1. Python is dynamically typed: it means that you don't declare a type (e.g. 'integer') for a variable name, and then assign something of that type (and only that type). Instead, you have variable names, and you bind them to entities whose type stays with the entity itself. a = 5 makes the variable name a to refer to the integer 5. Later, a = "hello" makes the variable name a to refer to a string containing "hello". Static typed languages would have you declare int a and then a = 5, but assigning a = "hello" would have been a compile time error. On one hand, this makes everything more unpredictable (you don't know what a refers to). On the other hand, it makes very easy to achieve some results a static typed languages makes very difficult.
  2. Python is strongly typed. It means that if a = "5" (the string whose value is '5') will remain a string, and never coerced to a number if the context requires so. Every type conversion in python must be done explicitly. This is different from, for example, Perl or Javascript, where you have weak typing, and can write things like "hello" + 5 to get "hello5".
  3. Python is object oriented, with class-based inheritance. Everything is an object (including classes, functions, modules, etc), in the sense that they can be passed around as arguments, have methods and attributes, and so on.
  4. Python is multipurpose: it is not specialised to a specific target of users (like R for statistics, or PHP for web programming). It is extended through modules and libraries, that hook very easily into the C programming language.
  5. Python enforces correct indentation of the code by making the indentation part of the syntax. There are no control braces in Python. Blocks of code are identified by the level of indentation. Although a big turn off for many programmers not used to this, it is precious as it gives a very uniform style and results in code that is visually pleasant to read.
  6. The code is compiled into byte code and then executed in a virtual machine. This means that precompiled code is portable between platforms.

Python can be used for any programming task, from GUI programming to web programming with everything else in between. It's quite efficient, as much of its activity is done at the C level. Python is just a layer on top of C. There are libraries for everything you can think of: game programming and openGL, GUI interfaces, web frameworks, semantic web, scientific computing...