Programs & Examples On #Wikipedia

Consider the tags wikipedia-api (or the more general mediawiki-api) and mediawiki. Questions should be related to programming.

Is there a Wikipedia API?

MediaWiki's API is running on Wikipedia (docs). You can also use the Special:Export feature to dump data and parse it yourself.

More information.

Is there a wikipedia API just for retrieve content summary?

There's a way to get the entire "intro section" without any html parsing! Similar to AnthonyS's answer with an additional explaintext param, you can get the intro section text in plain text.

Query

Getting Stack Overflow's intro in plain text:

Using page title:

https://en.wikipedia.org/w/api.php?format=json&action=query&prop=extracts&exintro&explaintext&redirects=1&titles=Stack%20Overflow

or use pageids

https://en.wikipedia.org/w/api.php?format=json&action=query&prop=extracts&exintro&explaintext&redirects=1&pageids=21721040

JSON Response

(warnings stripped)

{
    "query": {
        "pages": {
            "21721040": {
                "pageid": 21721040,
                "ns": 0,
                "title": "Stack Overflow",
                "extract": "Stack Overflow is a privately held website, the flagship site of the Stack Exchange Network, created in 2008 by Jeff Atwood and Joel Spolsky, as a more open alternative to earlier Q&A sites such as Experts Exchange. The name for the website was chosen by voting in April 2008 by readers of Coding Horror, Atwood's popular programming blog.\nIt features questions and answers on a wide range of topics in computer programming. The website serves as a platform for users to ask and answer questions, and, through membership and active participation, to vote questions and answers up or down and edit questions and answers in a fashion similar to a wiki or Digg. Users of Stack Overflow can earn reputation points and \"badges\"; for example, a person is awarded 10 reputation points for receiving an \"up\" vote on an answer given to a question, and can receive badges for their valued contributions, which represents a kind of gamification of the traditional Q&A site or forum. All user-generated content is licensed under a Creative Commons Attribute-ShareAlike license. Questions are closed in order to allow low quality questions to improve. Jeff Atwood stated in 2010 that duplicate questions are not seen as a problem but rather they constitute an advantage if such additional questions drive extra traffic to the site by multiplying relevant keyword hits in search engines.\nAs of April 2014, Stack Overflow has over 2,700,000 registered users and more than 7,100,000 questions. Based on the type of tags assigned to questions, the top eight most discussed topics on the site are: Java, JavaScript, C#, PHP, Android, jQuery, Python and HTML."
            }
        }
    }
}

Documentation: API: query/prop=extracts


Edit: Added &redirects=1 as recommended in comments. Edit: Added pageids example

jQuery.parseJSON throws “Invalid JSON” error due to escaped single quote in JSON

I was trying to save a JSON object from a XHR request into a HTML5 data-* attribute. I tried many of above solutions with no success.

What I finally end up doing was replacing the single quote ' with it code ' using a regex after the stringify() method call the following way:

var productToString = JSON.stringify(productObject);
var quoteReplaced = productToString.replace(/'/g, "'");
var anchor = '<a data-product=\'' + quoteReplaced + '\' href=\'#\'>' + productObject.name + '</a>';
// Here you can use the "anchor" variable to update your DOM element.

Regular expression to check if password is "8 characters including 1 uppercase letter, 1 special character, alphanumeric characters"

The regular expression you was looking for is: /^(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*[!@#\$%\^&\*\[\]"\';:_\-<>\., =\+\/\\]).{8,}$/u.

Example and test: http://regexr.com/3fhr4

In Java, what does NaN mean?

Taken from this page:

"NaN" stands for "not a number". "Nan" is produced if a floating point operation has some input parameters that cause the operation to produce some undefined result. For example, 0.0 divided by 0.0 is arithmetically undefined. Taking the square root of a negative number is also undefined.

Use table row coloring for cells in Bootstrap

With the current version of Bootstrap (3.3.7), it is possible to color a single cell of a table like so:

<td class = 'text-center col-md-4 success'>

Impersonate tag in Web.Config

Put the identity element before the authentication element

Twitter Bootstrap Datepicker within modal window

As mccannf said in his comment:

I recommend you look at your bootstrap CSS and JS. Your modal is being set at a very high z-index value (99999). Just compare my jsfiddle above with yours

How can I use SUM() OVER()

Seems like you expected the query to return running totals, but it must have given you the same values for both partitions of AccountID.

To obtain running totals with SUM() OVER (), you need to add an ORDER BY sub-clause after PARTITION BY …, like this:

SUM(Quantity) OVER (PARTITION BY AccountID ORDER BY ID)

But remember, not all database systems support ORDER BY in the OVER clause of a window aggregate function. (For instance, SQL Server didn't support it until the latest version, SQL Server 2012.)

Combine two pandas Data Frames (join on a common column)

In case anyone needs to try and merge two dataframes together on the index (instead of another column), this also works!

T1 and T2 are dataframes that have the same indices

import pandas as pd
T1 = pd.merge(T1, T2, on=T1.index, how='outer')

P.S. I had to use merge because append would fill NaNs in unnecessarily.

Native query with named parameter fails with "Not all named parameters have been set"

This was a bug fixed in version 4.3.11 https://hibernate.atlassian.net/browse/HHH-2851

EDIT: Best way to execute a native query is still to use NamedParameterJdbcTemplate It allows you need to retrieve a result that is not a managed entity ; you can use a RowMapper and even a Map of named parameters!

private NamedParameterJdbcTemplate namedParameterJdbcTemplate;

@Autowired
public void setDataSource(DataSource dataSource) {
    this.namedParameterJdbcTemplate = new NamedParameterJdbcTemplate(dataSource);
}

final List<Long> resultList = namedParameterJdbcTemplate.query(query, 
            mapOfNamedParamters, 
            new RowMapper<Long>() {
        @Override
        public Long mapRow(ResultSet rs, int rowNum) throws SQLException {
            return rs.getLong(1);
        }
    });

How to convert integer timestamp to Python datetime

datetime.datetime.fromtimestamp() is correct, except you are probably having timestamp in miliseconds (like in JavaScript), but fromtimestamp() expects Unix timestamp, in seconds.

Do it like that:

>>> import datetime
>>> your_timestamp = 1331856000000
>>> date = datetime.datetime.fromtimestamp(your_timestamp / 1e3)

and the result is:

>>> date
datetime.datetime(2012, 3, 16, 1, 0)

Does it answer your question?

EDIT: J.F. Sebastian correctly suggested to use true division by 1e3 (float 1000). The difference is significant, if you would like to get precise results, thus I changed my answer. The difference results from the default behaviour of Python 2.x, which always returns int when dividing (using / operator) int by int (this is called floor division). By replacing the divisor 1000 (being an int) with the 1e3 divisor (being representation of 1000 as float) or with float(1000) (or 1000. etc.), the division becomes true division. Python 2.x returns float when dividing int by float, float by int, float by float etc. And when there is some fractional part in the timestamp passed to fromtimestamp() method, this method's result also contains information about that fractional part (as the number of microseconds).

Compiler error: memset was not declared in this scope

You should include <string.h> (or its C++ equivalent, <cstring>).

Top 5 time-consuming SQL queries in Oracle

There are a number of possible ways to do this, but have a google for tkprof

There's no GUI... it's entirely command line and possibly a touch intimidating for Oracle beginners; but it's very powerful.

This link looks like a good start:

http://www.oracleutilities.com/OSUtil/tkprof.html

How can I add an item to a IEnumerable<T> collection?

Not only can you not add items like you state, but if you add an item to a List<T> (or pretty much any other non-read only collection) that you have an existing enumerator for, the enumerator is invalidated (throws InvalidOperationException from then on).

If you are aggregating results from some type of data query, you can use the Concat extension method:

Edit: I originally used the Union extension in the example, which is not really correct. My application uses it extensively to make sure overlapping queries don't duplicate results.

IEnumerable<T> itemsA = ...;
IEnumerable<T> itemsB = ...;
IEnumerable<T> itemsC = ...;
return itemsA.Concat(itemsB).Concat(itemsC);

Access VBA | How to replace parts of a string with another string

You could use a function similar to this also, it would allow you to add in different cases where you would like to change values:

Public Function strReplace(varValue As Variant) as Variant

    Select Case varValue

        Case "Avenue"
            strReplace = "Ave"

        Case "North"
            strReplace = "N"

        Case Else
            strReplace = varValue

    End Select

End Function

Then your SQL would read something like:

SELECT strReplace(Address) As Add FROM Tablename

Eclipse HotKey: how to switch between tabs?

One way to do it is to use the VI Plugin, and then you just do :n (and :N) to go between files.

That's what I do.

How to display a PDF via Android web browser without "downloading" first

I needed this too, and the links above stopped working so this is what I found to work with the New Google Drive:

Google has a service that creates the link for PDF's Not in GDrive: https://docs.google.com/viewer Just add your URL and it creates a link, and IFrame code (Look closely and you will see the pattern and create links without this web service)

Also, there is a way to do it for PDF's stored in Google Drive: https://docs.google.com/viewer?srcid=YOUR_GDRIVE_PDF_DOC_ID_HERE&pid=explorer&efh=false&a=v&chrome=false&embedded=true (this can be a link or the src URL of an iframe)

I've tested on Android and it brings up the PDF viewer nicely.

How to embed a PDF viewer in a page?

You could consider using PDFObject by Philip Hutchison.

Alternatively, if you're looking for a non-Javascript solution, you could use markup like this:

<object data="myfile.pdf" type="application/pdf" width="100%" height="100%">
  <p>Alternative text - include a link <a href="myfile.pdf">to the PDF!</a></p>
</object>

Are string.Equals() and == operator really same?

An object is defined by an OBJECT_ID, which is unique. If A and B are objects and A == B is true, then they are the very same object, they have the same data and methods, but, this is also true:

A.OBJECT_ID == B.OBJECT_ID

if A.Equals(B) is true, that means that the two objects are in the same state, but this doesn't mean that A is the very same as B.

Strings are objects.

Note that the == and Equals operators are reflexive, simetric, tranzitive, so they are equivalentic relations (to use relational algebraic terms)

What this means: If A, B and C are objects, then:

(1) A == A is always true; A.Equals(A) is always true (reflexivity)

(2) if A == B then B == A; If A.Equals(B) then B.Equals(A) (simetry)

(3) if A == B and B == C, then A == C; if A.Equals(B) and B.Equals(C) then A.Equals(C) (tranzitivity)

Also, you can note that this is also true:

(A == B) => (A.Equals(B)), but the inverse is not true.

A B =>
0 0 1
0 1 1
1 0 0
1 1 1

Example of real life: Two Hamburgers of the same type have the same properties: they are objects of the Hamburger class, their properties are exactly the same, but they are different entities. If you buy these two Hamburgers and eat one, the other one won't be eaten. So, the difference between Equals and ==: You have hamburger1 and hamburger2. They are exactly in the same state (the same weight, the same temperature, the same taste), so hamburger1.Equals(hamburger2) is true. But hamburger1 == hamburger2 is false, because if the state of hamburger1 changes, the state of hamburger2 not necessarily change and vice versa.

If you and a friend get a Hamburger, which is yours and his in the same time, then you must decide to split the Hamburger into two parts, because you.getHamburger() == friend.getHamburger() is true and if this happens: friend.eatHamburger(), then your Hamburger will be eaten too.

I could write other nuances about Equals and ==, but I'm getting hungry, so I have to go.

Best regards, Lajos Arpad.

Decimal to Hexadecimal Converter in Java

I need a function that takes in an int dec and returns a String hex.

I found a more elegant solution from http://introcs.cs.princeton.edu/java/31datatype/Hex2Decimal.java.html . I changed a bit from the original ( see the edit )

// precondition:  d is a nonnegative integer
public static String decimal2hex(int d) {
    String digits = "0123456789ABCDEF";
    if (d <= 0) return "0";
    int base = 16;   // flexible to change in any base under 16
    String hex = "";
    while (d > 0) {
        int digit = d % base;              // rightmost digit
        hex = digits.charAt(digit) + hex;  // string concatenation
        d = d / base;
    }
    return hex;
}

Disclaimer: I ask this question in my coding interview. I hope this solution doesn't get too popular :)

Edit June 17 2016 : I added the base variable to give the flexibility to change into any base : binary, octal, base of 7 ...
According to the comments, this solution is the most elegant so I removed the implementation of Integer.toHexString() .

Edit September 4 2015 : I found a more elegant solution http://introcs.cs.princeton.edu/java/31datatype/Hex2Decimal.java.html

How to use UIPanGestureRecognizer to move object? iPhone/iPad

if ([recognizer state] == UIGestureRecognizerStateChanged)    
{
    CGPoint translation1 = [recognizer translationInView:main_view];
    img12.center=CGPointMake(img12.center.x+translation1.x, img12.center.y+ translation1.y);
    [recognizer setTranslation:CGPointMake(0, 0) inView:main_view];

    recognizer.view.center=CGPointMake(recognizer.view.center.x+translation1.x, recognizer.view.center.y+ translation1.y);
}

-(void)move:(UIPanGestureRecognizer*)recognizer
{
    if ([recognizer state] == UIGestureRecognizerStateChanged)    
    {
        CGPoint translation = [recognizer translationInView:self.view];
        recognizer.view.center=CGPointMake(recognizer.view.center.x+translation.x, recognizer.view.center.y+ translation.y);
        [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
    }
}

Failed to load resource: the server responded with a status of 404 (Not Found) error in server

Use your browser's network inspector (F12) to see when the browser is requesting the bgbody.png image and what absolute path it's using and why the server is returning a 404 response.

...assuming that bgbody.png actually exists :)

Is your CSS in a stylesheet file or in a <style> block in a page? If it's in a stylesheet then the relative path must be relative to the CSS stylesheet (not the document that references it). If it's in a page then it must be relative to the current resource path. If you're using non-filesystem-based resource paths (i.e. using URL rewriting or URL routing) then this will cause problems and it's best to always use absolute paths.

Going by your relative path it looks like you store your images separately from your stylesheets. I don't think this is a good idea - I support storing images and other resources, like fonts, in the same directory as the stylesheet itself, as it simplifies paths and is also a more logical filesystem arrangement.

Number of rows affected by an UPDATE in PL/SQL

Use the Count(*) analytic function OVER PARTITION BY NULL This will count the total # of rows

Python csv string to array

You can convert a string to a file object using io.StringIO and then pass that to the csv module:

from io import StringIO
import csv

scsv = """text,with,Polish,non-Latin,letters
1,2,3,4,5,6
a,b,c,d,e,f
ges,zólty,waz,idzie,waska,drózka,
"""

f = StringIO(scsv)
reader = csv.reader(f, delimiter=',')
for row in reader:
    print('\t'.join(row))

simpler version with split() on newlines:

reader = csv.reader(scsv.split('\n'), delimiter=',')
for row in reader:
    print('\t'.join(row))

Or you can simply split() this string into lines using \n as separator, and then split() each line into values, but this way you must be aware of quoting, so using csv module is preferred.

On Python 2 you have to import StringIO as

from StringIO import StringIO

instead.

Send value of submit button when form gets posted

The button names are not submit, so the php $_POST['submit'] value is not set. As in isset($_POST['submit']) evaluates to false.

<html>
<form action="" method="post">
    <input type="hidden" name="action" value="submit" />
    <select name="name">
        <option>John</option>
        <option>Henry</option>
    <select>
<!-- 
make sure all html elements that have an ID are unique and name the buttons submit 
-->
    <input id="tea-submit" type="submit" name="submit" value="Tea">
    <input id="coffee-submit" type="submit" name="submit" value="Coffee">
</form>
</html>

<?php
if (isset($_POST['action'])) {
    echo '<br />The ' . $_POST['submit'] . ' submit button was pressed<br />';
}
?>

Find the min/max element of an array in JavaScript

You can use Array.sort but you'll have to write a simple number sorting function since the default is alphabetic.

Look at example 2 here.

Then you can grab arr[0] and arr[arr.length-1] to get min and max.

How to create a custom scrollbar on a div (Facebook style)

This link should get you started. Long story short, a div that has been styled to look like a scrollbar is used to catch click-and-drag events. Wired up to these events are methods that scroll the contents of another div which is set to an arbitrary height and typically has a css rule of overflow:scroll (there are variants on the css rules but you get the idea).

I'm all about the learning experience -- but after you've learned how it works, I recommend using a library (of which there are many) to do it. It's one of those "don't reinvent" things...

Chain-calling parent initialisers in python

Python 3 includes an improved super() which allows use like this:

super().__init__(args)

How to get Node.JS Express to listen only on localhost?

Thanks for the info, think I see the problem. This is a bug in hive-go that only shows up when you add a host. The last lines of it are:

app.listen(3001);
console.log("... port %d in %s mode", app.address().port, app.settings.env);

When you add the host on the first line, it is crashing when it calls app.address().port.

The problem is the potentially asynchronous nature of .listen(). Really it should be doing that console.log call inside a callback passed to listen. When you add the host, it tries to do a DNS lookup, which is async. So when that line tries to fetch the address, there isn't one yet because the DNS request is running, so it crashes.

Try this:

app.listen(3001, 'localhost', function() {
  console.log("... port %d in %s mode", app.address().port, app.settings.env);
});

How can one pull the (private) data of one's own Android app?

I had the same problem but solved it running following:

$ adb shell
$ run-as {app-package-name}
$ cd /data/data/{app-package-name}
$ chmod 777 {file}
$ cp {file} /mnt/sdcard/

After this you can run

$ adb pull /mnt/sdcard/{file}

Change Primary Key

Sometimes when we do these steps:

 alter table my_table drop constraint my_pk; 
 alter table my_table add constraint my_pk primary key (city_id, buildtime, time);

The last statement fails with

ORA-00955 "name is already used by an existing object"

Oracle usually creates an unique index with the same name my_pk. In such a case you can drop the unique index or rename it based on whether the constraint is still relevant.

You can combine the dropping of primary key constraint and unique index into a single sql statement:

alter table my_table drop constraint my_pk drop index; 

check this: ORA-00955 "name is already used by an existing object"

How to include another XHTML in XHTML using JSF 2.0 Facelets?

Included page:

<!-- opening and closing tags of included page -->
<ui:composition ...>
</ui:composition>

Including page:

<!--the inclusion line in the including page with the content-->
<ui:include src="yourFile.xhtml"/>
  • You start your included xhtml file with ui:composition as shown above.
  • You include that file with ui:include in the including xhtml file as also shown above.

Is recursion ever faster than looping?

is recursion ever faster than a loop?

No, Iteration will always be faster than Recursion. (in a Von Neumann Architecture)

Explanation:

If you build the minimum operations of a generic computer from scratch, "Iteration" comes first as a building block and is less resource intensive than "recursion", ergo is faster.

Building a pseudo-computing-machine from scratch:

Question yourself: What do you need to compute a value, i.e. to follow an algorithm and reach a result?

We will establish a hierarchy of concepts, starting from scratch and defining in first place the basic, core concepts, then build second level concepts with those, and so on.

  1. First Concept: Memory cells, storage, State. To do something you need places to store final and intermediate result values. Let’s assume we have an infinite array of "integer" cells, called Memory, M[0..Infinite].

  2. Instructions: do something - transform a cell, change its value. alter state. Every interesting instruction performs a transformation. Basic instructions are:

    a) Set & move memory cells

    • store a value into memory, e.g.: store 5 m[4]
    • copy a value to another position: e.g.: store m[4] m[8]

    b) Logic and arithmetic

    • and, or, xor, not
    • add, sub, mul, div. e.g. add m[7] m[8]
  3. An Executing Agent: a core in a modern CPU. An "agent" is something that can execute instructions. An Agent can also be a person following the algorithm on paper.

  4. Order of steps: a sequence of instructions: i.e.: do this first, do this after, etc. An imperative sequence of instructions. Even one line expressions are "an imperative sequence of instructions". If you have an expression with a specific "order of evaluation" then you have steps. It means than even a single composed expression has implicit “steps” and also has an implicit local variable (let’s call it “result”). e.g.:

    4 + 3 * 2 - 5
    (- (+ (* 3 2) 4 ) 5)
    (sub (add (mul 3 2) 4 ) 5)  
    

    The expression above implies 3 steps with an implicit "result" variable.

    // pseudocode
    
           1. result = (mul 3 2)
           2. result = (add 4 result)
           3. result = (sub result 5)
    

    So even infix expressions, since you have a specific order of evaluation, are an imperative sequence of instructions. The expression implies a sequence of operations to be made in a specific order, and because there are steps, there is also an implicit "result" intermediate variable.

  5. Instruction Pointer: If you have a sequence of steps, you have also an implicit "instruction pointer". The instruction pointer marks the next instruction, and advances after the instruction is read but before the instruction is executed.

    In this pseudo-computing-machine, the Instruction Pointer is part of Memory. (Note: Normally the Instruction Pointer will be a “special register” in a CPU core, but here we will simplify the concepts and assume all data (registers included) are part of “Memory”)

  6. Jump - Once you have an ordered number of steps and an Instruction Pointer, you can apply the "store" instruction to alter the value of the Instruction Pointer itself. We will call this specific use of the store instruction with a new name: Jump. We use a new name because is easier to think about it as a new concept. By altering the instruction pointer we're instructing the agent to “go to step x“.

  7. Infinite Iteration: By jumping back, now you can make the agent "repeat" a certain number of steps. At this point we have infinite Iteration.

                       1. mov 1000 m[30]
                       2. sub m[30] 1
                       3. jmp-to 2  // infinite loop
    
  8. Conditional - Conditional execution of instructions. With the "conditional" clause, you can conditionally execute one of several instructions based on the current state (which can be set with a previous instruction).

  9. Proper Iteration: Now with the conditional clause, we can escape the infinite loop of the jump back instruction. We have now a conditional loop and then proper Iteration

    1. mov 1000 m[30]
    2. sub m[30] 1
    3. (if not-zero) jump 2  // jump only if the previous 
                            // sub instruction did not result in 0
    
    // this loop will be repeated 1000 times
    // here we have proper ***iteration***, a conditional loop.
    
  10. Naming: giving names to a specific memory location holding data or holding a step. This is just a "convenience" to have. We do not add any new instructions by having the capacity to define “names” for memory locations. “Naming” is not a instruction for the agent, it’s just a convenience to us. Naming makes code (at this point) easier to read and easier to change.

       #define counter m[30]   // name a memory location
       mov 1000 counter
    loop:                      // name a instruction pointer location
        sub counter 1
        (if not-zero) jmp-to loop  
    
  11. One-level subroutine: Suppose there’s a series of steps you need to execute frequently. You can store the steps in a named position in memory and then jump to that position when you need to execute them (call). At the end of the sequence you'll need to return to the point of calling to continue execution. With this mechanism, you’re creating new instructions (subroutines) by composing core instructions.

    Implementation: (no new concepts required)

    • Store the current Instruction Pointer in a predefined memory position
    • jump to the subroutine
    • at the end of the subroutine, you retrieve the Instruction Pointer from the predefined memory location, effectively jumping back to the following instruction of the original call

    Problem with the one-level implementation: You cannot call another subroutine from a subroutine. If you do, you'll overwrite the returning address (global variable), so you cannot nest calls.

    To have a better Implementation for subroutines: You need a STACK

  12. Stack: You define a memory space to work as a "stack", you can “push” values on the stack, and also “pop” the last “pushed” value. To implement a stack you'll need a Stack Pointer (similar to the Instruction Pointer) which points to the actual “head” of the stack. When you “push” a value, the stack pointer decrements and you store the value. When you “pop”, you get the value at the actual Stack Pointer and then the Stack Pointer is incremented.

  13. Subroutines Now that we have a stack we can implement proper subroutines allowing nested calls. The implementation is similar, but instead of storing the Instruction Pointer in a predefined memory position, we "push" the value of the IP in the stack. At the end of the subroutine, we just “pop” the value from the stack, effectively jumping back to the instruction after the original call. This implementation, having a “stack” allows calling a subroutine from another subroutine. With this implementation we can create several levels of abstraction when defining new instructions as subroutines, by using core instructions or other subroutines as building blocks.

  14. Recursion: What happens when a subroutine calls itself?. This is called "recursion".

    Problem: Overwriting the local intermediate results a subroutine can be storing in memory. Since you are calling/reusing the same steps, if the intermediate result are stored in predefined memory locations (global variables) they will be overwritten on the nested calls.

    Solution: To allow recursion, subroutines should store local intermediate results in the stack, therefore, on each recursive call (direct or indirect) the intermediate results are stored in different memory locations.

...

having reached recursion we stop here.

Conclusion:

In a Von Neumann Architecture, clearly "Iteration" is a simpler/basic concept than “Recursion". We have a form of "Iteration" at level 7, while "Recursion" is at level 14 of the concepts hierarchy.

Iteration will always be faster in machine code because it implies less instructions therefore less CPU cycles.

Which one is "better"?

  • You should use "iteration" when you are processing simple, sequential data structures, and everywhere a “simple loop” will do.

  • You should use "recursion" when you need to process a recursive data structure (I like to call them “Fractal Data Structures”), or when the recursive solution is clearly more “elegant”.

Advice: use the best tool for the job, but understand the inner workings of each tool in order to choose wisely.

Finally, note that you have plenty of opportunities to use recursion. You have Recursive Data Structures everywhere, you’re looking at one now: parts of the DOM supporting what you are reading are a RDS, a JSON expression is a RDS, the hierarchical file system in your computer is a RDS, i.e: you have a root directory, containing files and directories, every directory containing files and directories, every one of those directories containing files and directories...

My prerelease app has been "processing" for over a week in iTunes Connect, what gives?

We had a similar issue. Uploaded builds were queueing up and it simply said "Processing" with the popup help, “After builds are uploaded they will go through a processing state before they can be used.” Days passed.

Selecting "Internal Testers," making a change, and saving seemed to immediately clear the queue: The latest build was now active and available for testing. I've done this twice with two different apps now.

Update: At this point, all bets are off. It seems "processing" happens when Apple quietly upgrades iTunes Connect and there's nothing you can do about it.

On September 23, 2015 iTunes Connect didn't accept any uploads for nearly 24 hours. The "Internal Testers" trick didn't work. Eventually bumping the version number (to avoid "duplicate binary" error) and re-submitting worked.

The next day, Surprise! iTunes Connect was completely changed. I guess we were all looking at a dead site while they brought up the new version in the background :(

In our case we can still see dozens of "failed" uploads still sitting in the "processing" state. Oh well.

Some people report using Application Loader works better than Xcode for submitting builds to iTunes Connect. You can find it inside Xcode now, under the Xcode menu "Open Developer Tool" item.

Sometimes this works. Sometimes it doesn't. Your milage may vary ¯\_(?)_/¯

How to represent matrices in python

Python doesn't have matrices. You can use a list of lists or NumPy

How to generate a number of most distinctive colors in R?

I found a website offering a list of 20 distinctive colours: https://sashat.me/2017/01/11/list-of-20-simple-distinct-colors/

col_vector<-c('#e6194b', '#3cb44b', '#ffe119', '#4363d8', '#f58231', '#911eb4', '#46f0f0', '#f032e6', '#bcf60c', '#fabebe', '#008080', '#e6beff', '#9a6324', '#fffac8', '#800000', '#aaffc3', '#808000', '#ffd8b1', '#000075', '#808080', '#ffffff', '#000000')

You can have a try!

Testing if value is a function

You could simply use the typeof operator along with a ternary operator for short:

onsubmit="return typeof valid =='function' ? valid() : true;"

If it is a function we call it and return it's return value, otherwise just return true

Edit:

I'm not quite sure what you really want to do, but I'll try to explain what might be happening.

When you declare your onsubmit code within your html, it gets turned into a function and thus its callable from the JavaScript "world". That means that those two methods are equivalent:

HTML: <form onsubmit="return valid();" />
JavaScript: myForm.onsubmit = function() { return valid(); };

These two will be both functions and both will be callable. You can test any of those using the typeof operator which should yeld the same result: "function".

Now if you assign a string to the "onsubmit" property via JavaScript, it will remain a string, hence not callable. Notice that if you apply the typeof operator against it, you'll get "string" instead of "function".

I hope this might clarify a few things. Then again, if you want to know if such property (or any identifier for the matter) is a function and callable, the typeof operator should do the trick. Although I'm not sure if it works properly across multiple frames.

Cheers

How can I compare two time strings in the format HH:MM:SS?

As Felix Kling said in the comments, provided your times are based on a 24 hour clock (and they should be if there's no AM/PM) and provided they are always in the format HH:MM:SS you can do a direct string comparison:

var str1 = "10:20:45",
    str2 = "05:10:10";

if (str1 > str2)
    alert("Time 1 is later than time 2");
else
    alert("Time 2 is later than time 1");

How do I escape spaces in path for scp copy in Linux?

Basically you need to escape it twice, because it's escaped locally and then on the remote end.

There are a couple of options you can do (in bash):

scp [email protected]:"'web/tmp/Master File 18 10 13.xls'" .
scp [email protected]:"web/tmp/Master\ File\ 18\ 10\ 13.xls" .
scp [email protected]:web/tmp/Master\\\ File\\\ 18\\\ 10\\\ 13.xls .

Eclipse - Failed to create the java virtual machine

I tried several methods but didn't work. The only one that did is the one right at the bottom. I'll just list the other options I tried as well, for reference.

Some background, I migrated from Mars to Neon and copied over eclipse.ini almost exactly.

Reduce -XX:MaxPermSize and -Xmx

Like other answers have mentioned, progressively reduce these 2 flags (eg to 128m) and try again. If it still doesn't work at 128m then try other options below.

Find the offending flag by renaming eclipse.ini

Jon H's answer gave me a hint. Delete eclipse.ini (or rename it) and start eclipse. It should regen eclipse.ini and launch successfully (mine didn't regen eclipse.ini though eclipse launched fine).

If eclipse.ini did regen for you, then add each flag back one-by-one.

If not, revert the original eclipse.ini and remove each flag one-by-one until you've found the flag that causes an error.

For my case, I upgraded from Mars to Neon. The offending flag was -XX:+UseG1GC Removing this flag (and only this flag) worked for me. Setting back -Xmx and -XX:MaxPermSize to 1G worked for me as well.

How to fix git error: RPC failed; curl 56 GnuTLS

I had a similar fault:

error: RPC failed; curl 56 GnuTLS recv error (-9): A TLS packet with unexpected length was received.

when trying to clone a repository from Github.

After trying most of the solutions posted here, none of which worked, it turned out to be the parental controls on our home network. Turning these parental controls off solved the problem.

How to get summary statistics by group

While some of the other approaches work, this is pretty close to what you were doing and only uses base r. If you know the aggregate command this may be more intuitive.

with( df , aggregate( dt , by=list(group) , FUN=summary)  )

Undefined reference to pthread_create in Linux

You need to use the option -lpthread with gcc.

Converting milliseconds to a date (jQuery/JavaScript)

If you want custom formatting for your date I offer a simple function for it:

var now = new Date;
console.log( now.customFormat( "#DD#/#MM#/#YYYY# #hh#:#mm#:#ss#" ) );

Here are the tokens supported:

token:     description:             example:
#YYYY#     4-digit year             1999
#YY#       2-digit year             99
#MMMM#     full month name          February
#MMM#      3-letter month name      Feb
#MM#       2-digit month number     02
#M#        month number             2
#DDDD#     full weekday name        Wednesday
#DDD#      3-letter weekday name    Wed
#DD#       2-digit day number       09
#D#        day number               9
#th#       day ordinal suffix       nd
#hhhh#     2-digit 24-based hour    17
#hhh#      military/24-based hour   17
#hh#       2-digit hour             05
#h#        hour                     5
#mm#       2-digit minute           07
#m#        minute                   7
#ss#       2-digit second           09
#s#        second                   9
#ampm#     "am" or "pm"             pm
#AMPM#     "AM" or "PM"             PM

And here's the code:

//*** This code is copyright 2002-2016 by Gavin Kistner, [email protected]
//*** It is covered under the license viewable at http://phrogz.net/JS/_ReuseLicense.txt
Date.prototype.customFormat = function(formatString){
  var YYYY,YY,MMMM,MMM,MM,M,DDDD,DDD,DD,D,hhhh,hhh,hh,h,mm,m,ss,s,ampm,AMPM,dMod,th;
  YY = ((YYYY=this.getFullYear())+"").slice(-2);
  MM = (M=this.getMonth()+1)<10?('0'+M):M;
  MMM = (MMMM=["January","February","March","April","May","June","July","August","September","October","November","December"][M-1]).substring(0,3);
  DD = (D=this.getDate())<10?('0'+D):D;
  DDD = (DDDD=["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"][this.getDay()]).substring(0,3);
  th=(D>=10&&D<=20)?'th':((dMod=D%10)==1)?'st':(dMod==2)?'nd':(dMod==3)?'rd':'th';
  formatString = formatString.replace("#YYYY#",YYYY).replace("#YY#",YY).replace("#MMMM#",MMMM).replace("#MMM#",MMM).replace("#MM#",MM).replace("#M#",M).replace("#DDDD#",DDDD).replace("#DDD#",DDD).replace("#DD#",DD).replace("#D#",D).replace("#th#",th);
  h=(hhh=this.getHours());
  if (h==0) h=24;
  if (h>12) h-=12;
  hh = h<10?('0'+h):h;
  hhhh = hhh<10?('0'+hhh):hhh;
  AMPM=(ampm=hhh<12?'am':'pm').toUpperCase();
  mm=(m=this.getMinutes())<10?('0'+m):m;
  ss=(s=this.getSeconds())<10?('0'+s):s;
  return formatString.replace("#hhhh#",hhhh).replace("#hhh#",hhh).replace("#hh#",hh).replace("#h#",h).replace("#mm#",mm).replace("#m#",m).replace("#ss#",ss).replace("#s#",s).replace("#ampm#",ampm).replace("#AMPM#",AMPM);
};

CSS - center two images in css side by side

You can't have two elements with the same ID.

Aside from that, you are defining them as block elemnts, meaning (in layman's terms) that they are being forced to appear on their own line.

Instead, try something like this:

<div class="link"><a href="..."><img src="..."... /></a></div>
<div class="link"><a href="..."><img src="..."... /></a></div>

CSS:

.link {
    width: 50%;
    float: left;
    text-align: center;
}

Execute a terminal command from a Cocoa app

Here's how to do it in Swift

Changes for Swift 3.0:

  • NSPipe has been renamed Pipe

  • NSTask has been renamed Process


This is based on inkit's Objective-C answer above. He wrote it as a category on NSString — For Swift, it becomes an extension of String.

extension  String.runAsCommand()  ->  String

extension String {
    func runAsCommand() -> String {
        let pipe = Pipe()
        let task = Process()
        task.launchPath = "/bin/sh"
        task.arguments = ["-c", String(format:"%@", self)]
        task.standardOutput = pipe
        let file = pipe.fileHandleForReading
        task.launch()
        if let result = NSString(data: file.readDataToEndOfFile(), encoding: String.Encoding.utf8.rawValue) {
            return result as String
        }
        else {
            return "--- Error running command - Unable to initialize string from file data ---"
        }
    }
}

Usage:

let input = "echo hello"
let output = input.runAsCommand()
print(output)                        // prints "hello"

    or just:

print("echo hello".runAsCommand())   // prints "hello" 

Example:

@IBAction func toggleFinderShowAllFiles(_ sender: AnyObject) {

    var newSetting = ""
    let readDefaultsCommand = "defaults read com.apple.finder AppleShowAllFiles"

    let oldSetting = readDefaultsCommand.runAsCommand()

    // Note: the Command results are terminated with a newline character

    if (oldSetting == "0\n") { newSetting = "1" }
    else { newSetting = "0" }

    let writeDefaultsCommand = "defaults write com.apple.finder AppleShowAllFiles \(newSetting) ; killall Finder"

    _ = writeDefaultsCommand.runAsCommand()

}

Note the Process result as read from the Pipe is an NSString object. It might be an error string and it can also be an empty string, but it should always be an NSString.

So, as long as it's not nil, the result can cast as a Swift String and returned.

If for some reason no NSString at all can be initialized from the file data, the function returns an error message. The function could have been written to return an optional String?, but that would be awkward to use and wouldn't serve a useful purpose because it's so unlikely for this to occur.

What is the difference between class and instance methods?

Class methods can't change or know the value of any instance variable. That should be the criteria for knowing if an instance method can be a class method.

Converting from hex to string

 string hexString = "8E2";
 int num = Int32.Parse(hexString, System.Globalization.NumberStyles.HexNumber);
 Console.WriteLine(num);
 //Output: 2274

From https://msdn.microsoft.com/en-us/library/bb311038.aspx

ObjectiveC Parse Integer from String

Keep in mind that international users may be using a decimal separator other than . in which case values can get mixed up or just become nil when using intValue on a string.

For example, in the UK 1.23 is written 1,23, so the number 1.777 would be input by user as 1,777, which, as .intValue, will be 1777 not 1 (truncated).


I've made a macro that will convert input text to an NSNumber based on a locale argument which can be nil (if nil it uses device current locale).

#define stringToNumber(__string, __nullable_locale) (\
(^NSNumber *(void){\
NSLocale *__locale = __nullable_locale;\
if (!__locale) {\
__locale = [NSLocale currentLocale];\
}\
NSString *__string_copy = [__string stringByReplacingOccurrencesOfString:__locale.groupingSeparator withString:@""];\
__string_copy = [__string_copy stringByReplacingOccurrencesOfString:__locale.decimalSeparator withString:@"."];\
return @([__string_copy doubleValue]);\
})()\
)

No authenticationScheme was specified, and there was no DefaultChallengeScheme found with default authentification and custom authorization

Your initial statement in the marked solution isn't entirely true. While your new solution may accomplish your original goal, it is still possible to circumvent the original error while preserving your AuthorizationHandler logic--provided you have basic authentication scheme handlers in place, even if they are functionally skeletons.

Speaking broadly, Authentication Handlers and schemes are meant to establish + validate identity, which makes them required for Authorization Handlers/policies to function--as they run on the supposition that an identity has already been established.

ASP.NET Dev Haok summarizes this best best here: "Authentication today isn't aware of authorization at all, it only cares about producing a ClaimsPrincipal per scheme. Authorization has to be aware of authentication somewhat, so AuthenticationSchemes in the policy is a mechanism for you to associate the policy with schemes used to build the effective claims principal for authorization (or it just uses the default httpContext.User for the request, which does rely on DefaultAuthenticateScheme)." https://github.com/aspnet/Security/issues/1469

In my case, the solution I'm working on provided its own implicit concept of identity, so we had no need for authentication schemes/handlers--just header tokens for authorization. So until our identity concepts changes, our header token authorization handlers that enforce the policies can be tied to 1-to-1 scheme skeletons.

Tags on endpoints:

[Authorize(AuthenticationSchemes = "AuthenticatedUserSchemeName", Policy = "AuthorizedUserPolicyName")]

Startup.cs:

        services.AddAuthentication(options =>
        {
            options.DefaultAuthenticateScheme = "AuthenticatedUserSchemeName";
        }).AddScheme<ValidTokenAuthenticationSchemeOptions, ValidTokenAuthenticationHandler>("AuthenticatedUserSchemeName", _ => { });

        services.AddAuthorization(options =>
        {
            options.AddPolicy("AuthorizedUserPolicyName", policy =>
            {
                //policy.RequireClaim(ClaimTypes.Sid,"authToken");
                policy.AddAuthenticationSchemes("AuthenticatedUserSchemeName");
                policy.AddRequirements(new ValidTokenAuthorizationRequirement());
            });
            services.AddSingleton<IAuthorizationHandler, ValidTokenAuthorizationHandler>();

Both the empty authentication handler and authorization handler are called (similar in setup to OP's respective posts) but the authorization handler still enforces our authorization policies.

Call ASP.NET function from JavaScript?

Add this line to page load if you are getting object expected error.

ClientScript.GetPostBackEventReference(this, "");

Any way to generate ant build.xml file automatically from Eclipse?

I've had the same problem, our work environment is based on Eclipse Java projects, and we needed to build automatically an ANT file so that we could use a continuous integration server (Jenkins, in our case).

We rolled out our own Eclipse Java to Ant tool, which is now available on GitHub:

ant-build-for-java

To use it, call:

java -jar ant-build-for-java.jar <folder with repositories> [<.userlibraries file>]

The first argument is the folder with the repositories. It will search the folder recursively for any .project file. The tool will create a build.xml in the given folder.

Optionally, the second argument can be an exported .userlibraries file, from Eclipse, needed when any of the projects use Eclipse user libraries. The tool was tested only with user libraries using relative paths, it's how we use them in our repo. This implies that JARs and other archives needed by projects are inside an Eclipse project, and referenced from there.

The tool only supports dependencies from other Eclipse projects and from Eclipse user libraries.

Getting file size in Python?

Use os.path.getsize(path) which will

Return the size, in bytes, of path. Raise OSError if the file does not exist or is inaccessible.

import os
os.path.getsize('C:\\Python27\\Lib\\genericpath.py')

Or use os.stat(path).st_size

import os
os.stat('C:\\Python27\\Lib\\genericpath.py').st_size 

Or use Path(path).stat().st_size (Python 3.4+)

from pathlib import Path
Path('C:\\Python27\\Lib\\genericpath.py').stat().st_size

push multiple elements to array

If you want to add multiple items, you have to use the spread operator

a = [1,2]
b = [3,4,5,6]
a.push(...b)

The output will be

a = [1,2,3,4,5,6]

Is it possible to use "return" in stored procedure?

In Stored procedure, you return the values using OUT parameter ONLY. As you have defined two variables in your example:

   outstaticip OUT VARCHAR2, outcount OUT NUMBER

Just assign the return values to the out parameters i.e. outstaticip and outcount and access them back from calling location. What I mean here is: when you call the stored procedure, you will be passing those two variables as well. After the stored procedure call, the variables will be populated with return values.

If you want to have RETURN value as return from the PL/SQL call, then use FUNCTION. Please note that in case, you would be able to return only one variable as return variable.

What's the valid way to include an image with no src?

As written in comments, this method is wrong.

I didn't find this answer before, but acording to W3 Specs valid empty src tag would be an anchor link #.

Example: src="#", src="#empty"

Page validates successfully and no extra request are made.

Given the lat/long coordinates, how can we find out the city/country?

An Open Source alternative is Nominatim from Open Street Map. All you have to do is set the variables in an URL and it returns the city/country of that location. Please check the following link for official documentation: Nominatim

How to save data file into .RData?

There are three ways to save objects from your R session:

Saving all objects in your R session:

The save.image() function will save all objects currently in your R session:

save.image(file="1.RData") 

These objects can then be loaded back into a new R session using the load() function:

load(file="1.RData")

Saving some objects in your R session:

If you want to save some, but not all objects, you can use the save() function:

save(city, country, file="1.RData")

Again, these can be reloaded into another R session using the load() function:

load(file="1.RData") 

Saving a single object

If you want to save a single object you can use the saveRDS() function:

saveRDS(city, file="city.rds")
saveRDS(country, file="country.rds") 

You can load these into your R session using the readRDS() function, but you will need to assign the result into a the desired variable:

city <- readRDS("city.rds")
country <- readRDS("country.rds")

But this also means you can give these objects new variable names if needed (i.e. if those variables already exist in your new R session but contain different objects):

city_list <- readRDS("city.rds")
country_vector <- readRDS("country.rds")

Format price in the current locale and currency

This is a charming answer. Work well on any currency which is selected for store.

$formattedPrice = Mage::helper('core')->currency($finalPrice, true, false);

View array in Visual Studio debugger?

You can try this nice little trick for C++. Take the expression which gives you the array and then append a comma and the number of elements you want to see. Expanding that value will show you elements 0-(N-1) where N is the number you add after the comma.

For example if pArray is the array, type pArray,10 in the watch window.

foreach with index

You can do the following

foreach (var it in someCollection.Select((x, i) => new { Value = x, Index = i }) )
{
   if (it.Index > SomeNumber) //      
}

This will create an anonymous type value for every entry in the collection. It will have two properties

  • Value: with the original value in the collection
  • Index: with the index within the collection

A method to reverse effect of java String.split()?

If you have an int[], Arrays.toString() is the easiest way.

Determine if two rectangles overlap each other?

This is from exercise 3.28 from the book Introduction to Java Programming- Comprehensive Edition. The code tests whether the two rectangles are indenticle, whether one is inside the other and whether one is outside the other. If none of these condition are met then the two overlap.

**3.28 (Geometry: two rectangles) Write a program that prompts the user to enter the center x-, y-coordinates, width, and height of two rectangles and determines whether the second rectangle is inside the first or overlaps with the first, as shown in Figure 3.9. Test your program to cover all cases. Here are the sample runs:

Enter r1's center x-, y-coordinates, width, and height: 2.5 4 2.5 43 Enter r2's center x-, y-coordinates, width, and height: 1.5 5 0.5 3 r2 is inside r1

Enter r1's center x-, y-coordinates, width, and height: 1 2 3 5.5 Enter r2's center x-, y-coordinates, width, and height: 3 4 4.5 5 r2 overlaps r1

Enter r1's center x-, y-coordinates, width, and height: 1 2 3 3 Enter r2's center x-, y-coordinates, width, and height: 40 45 3 2 r2 does not overlap r1

import java.util.Scanner;

public class ProgrammingEx3_28 {
public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    System.out
            .print("Enter r1's center x-, y-coordinates, width, and height:");
    double x1 = input.nextDouble();
    double y1 = input.nextDouble();
    double w1 = input.nextDouble();
    double h1 = input.nextDouble();
    w1 = w1 / 2;
    h1 = h1 / 2;
    System.out
            .print("Enter r2's center x-, y-coordinates, width, and height:");
    double x2 = input.nextDouble();
    double y2 = input.nextDouble();
    double w2 = input.nextDouble();
    double h2 = input.nextDouble();
    w2 = w2 / 2;
    h2 = h2 / 2;

    // Calculating range of r1 and r2
    double x1max = x1 + w1;
    double y1max = y1 + h1;
    double x1min = x1 - w1;
    double y1min = y1 - h1;
    double x2max = x2 + w2;
    double y2max = y2 + h2;
    double x2min = x2 - w2;
    double y2min = y2 - h2;

    if (x1max == x2max && x1min == x2min && y1max == y2max
            && y1min == y2min) {
        // Check if the two are identicle
        System.out.print("r1 and r2 are indentical");

    } else if (x1max <= x2max && x1min >= x2min && y1max <= y2max
            && y1min >= y2min) {
        // Check if r1 is in r2
        System.out.print("r1 is inside r2");
    } else if (x2max <= x1max && x2min >= x1min && y2max <= y1max
            && y2min >= y1min) {
        // Check if r2 is in r1
        System.out.print("r2 is inside r1");
    } else if (x1max < x2min || x1min > x2max || y1max < y2min
            || y2min > y1max) {
        // Check if the two overlap
        System.out.print("r2 does not overlaps r1");
    } else {
        System.out.print("r2 overlaps r1");
    }

}
}

How to extract .war files in java? ZIP vs JAR

For mac users: in terminal command :

unzip yourWARfileName.war

How to use Morgan logger?

Using morgan is pretty much straightforward. As the documentation suggests, there are different ways to get your desired output with morgan. It comes with preconfigured logging methods or you can define one yourself. Eg.

const morgan = require('morgan')

app.use(morgan('tiny')

This will give you the preconfiguration called tiny. You will notice in your terminal what it does. In case you are not satisfied with this and you want deeper e.g. lets say the request url, then this is where tokens come in.

morgan.token('url', function (req, res){ return '/api/myendpoint' })

then use it like so:

app.use(morgan(' :url ')

Check the documentation its all highlighted there.

IE11 prevents ActiveX from running

There is no solution to this problem. As of IE11 on Windows 8, Microsoft no longer allows ActiveX plugins to run in its browser space. There is absolutely nothing that a third party developer can do about it.

A similar thing has recently happened with the Chrome browser which no longer supports NPAPI plugins. Instead Chrome only supports PPAPI plugins which are useless for system level tasks once performed by NPAPI plugins.

So developers needing browser support for system interactive plugins can only recommend either the Firefox browser or the ASPS web browser.

Python get current time in right timezone

To get the current time in the local timezone as a naive datetime object:

from datetime import datetime
naive_dt = datetime.now()

If it doesn't return the expected time then it means that your computer is misconfigured. You should fix it first (it is unrelated to Python).

To get the current time in UTC as a naive datetime object:

naive_utc_dt = datetime.utcnow()

To get the current time as an aware datetime object in Python 3.3+:

from datetime import datetime, timezone

utc_dt = datetime.now(timezone.utc) # UTC time
dt = utc_dt.astimezone() # local time

To get the current time in the given time zone from the tz database:

import pytz

tz = pytz.timezone('Europe/Berlin')
berlin_now = datetime.now(tz)

It works during DST transitions. It works if the timezone had different UTC offset in the past i.e., it works even if the timezone corresponds to multiple tzinfo objects at different times.

Clear variable in python

Do you want to delete a variable, don't you?

ok, I think I've got a best alternative idea to @bnaul's answer:

You can delete individual names with del:

del x

or you can remove them from the globals() object:

for name in dir():
    if not name.startswith('_'):
        del globals()[name]

This is just an example loop; it defensively only deletes names that do not start with an underscore, making a (not unreasoned) assumption that you only used names without an underscore at the start in your interpreter. You could use a hard-coded list of names to keep instead (whitelisting) if you really wanted to be thorough. There is no built-in function to do the clearing for you, other than just exit and restart the interpreter.

Modules you've imported (like import os) are going to remain imported because they are referenced by sys.modules; subsequent imports will reuse the already imported module object. You just won't have a reference to them in your current global namespace.

RegEx - Match Numbers of Variable Length

What regex engine are you using? Most of them will support the following expression:

\{\d+:\d+\}

The \d is actually shorthand for [0-9], but the important part is the addition of + which means "one or more".

Reading DataSet

DataSet resembles database. DataTable resembles database table, and DataRow resembles a record in a table. If you want to add filtering or sorting options, you then do so with a DataView object, and convert it back to a separate DataTable object.

If you're using database to store your data, then you first load a database table to a DataSet object in memory. You can load multiple database tables to one DataSet, and select specific table to read from the DataSet through DataTable object. Subsequently, you read a specific row of data from your DataTable through DataRow. Following codes demonstrate the steps:

SqlCeDataAdapter da = new SqlCeDataAdapter();
DataSet ds = new DataSet();
DataTable dt = new DataTable();

da.SelectCommand = new SqlCommand(@"SELECT * FROM FooTable", connString);
da.Fill(ds, "FooTable");
dt = ds.Tables["FooTable"];

foreach (DataRow dr in dt.Rows)
{
    MessageBox.Show(dr["Column1"].ToString());
}

To read a specific cell in a row:

int rowNum // row number
string columnName = "DepartureTime";  // database table column name
dt.Rows[rowNum][columnName].ToString();

Save the console.log in Chrome to a file

If you're running an Apache server on your localhost (don't do this on a production server), you can also post the results to a script instead of writing it to console.

So instead of console.log, you can write:

JSONP('http://localhost/save.php', {fn: 'filename.txt', data: json});

Then save.php can do this

<?php

 $fn = $_REQUEST['fn'];
 $data = $_REQUEST['data'];

 file_put_contents("path/$fn", $data);

Execute another jar in a Java program

.jar isn't executable. Instantiate classes or make call to any static method.

EDIT: Add Main-Class entry while creating a JAR.

>p.mf (content of p.mf)

Main-Class: pk.Test

>Test.java

package pk;
public class Test{
  public static void main(String []args){
    System.out.println("Hello from Test");
  }
}

Use Process class and it's methods,

public class Exec
{
   public static void main(String []args) throws Exception
    {
        Process ps=Runtime.getRuntime().exec(new String[]{"java","-jar","A.jar"});
        ps.waitFor();
        java.io.InputStream is=ps.getInputStream();
        byte b[]=new byte[is.available()];
        is.read(b,0,b.length);
        System.out.println(new String(b));
    }
}

Maximum packet size for a TCP connection

There're no packets in TCP API.

There're packets in underlying protocols often, like when TCP is done over IP, which you have no interest in, because they have nothing to do with the user except for very delicate performance optimizations which you are probably not interested in (according to the question's formulation).

If you ask what is a maximum number of bytes you can send() in one API call, then this is implementation and settings dependent. You would usually call send() for chunks of up to several kilobytes, and be always ready for the system to refuse to accept it totally or partially, in which case you will have to manually manage splitting into smaller chunks to feed your data into the TCP send() API.

How do you make strings "XML safe"?

Adding this in case it helps someone.

As I am working with Japanese characters, encoding has also been set appropriately. However, from time to time, I find that htmlentities and htmlspecialchars are not sufficient.

Some user inputs contain special characters that are not stripped by the above functions. In those cases I have to do this:

preg_replace('/[\x00-\x1f]/','',htmlspecialchars($string))

This will also remove certain xml-unsafe control characters like Null character or EOT. You can use this table to determine which characters you wish to omit.

Efficiently replace all accented characters in a string?

https://stackoverflow.com/a/37511463

With ES2015/ES6 String.Prototype.Normalize(),

const str = "Crème Brulée"
str.normalize('NFD').replace(/[\u0300-\u036f]/g, "")
> 'Creme Brulee'

Two things are happening here:

  1. normalize()ing to NFD Unicode normal form decomposes combined graphemes into the combination of simple ones. The è of Crème ends up expressed as e + `.
  2. Using a regex character class to match the U+0300 ? U+036F range, it is now trivial to globally get rid of the diacritics, which the Unicode standard conveniently groups as the Combining Diacritical Marks Unicode block.

See comment for performance testing.

Alternatively, if you just want sorting

Intl.Collator has sufficient support ~85% right now, a polyfill is also available here but I haven't tested it.

const c = new Intl.Collator();
['creme brulee', 'crème brulée', 'crame brulai', 'crome brouillé',
'creme brulay', 'creme brulfé', 'creme bruléa'].sort(c.compare)
[ 'crame brulai','creme brulay','creme bruléa','creme brulee',
'crème brulée','creme brulfé','crome brouillé' ]


['creme brulee', 'crème brulée', 'crame brulai', 'crome brouillé'].sort((a,b) => a>b)
["crame brulai", "creme brulee", "crome brouillé", "crème brulée"]

Switch android x86 screen resolution

Based on my experience, it's enough to use the following additional boot options:

UVESA_MODE=320x480 DPI=160

No need to add vga definition. Watch out for DPI value! As bigger one makes your icons bigger.

To add the previous boot options, go to debug mode (during grub menu selection)

mount -o remount,rw /mnt
vi /mnt/grub/menu.lst

Now edit on this line:

kernel /android-2.3-RC1/kernel quiet root=/dev/ram0 androidboot_hardware=eeepc acpi_sleep=s3_bios,s3_mode SRC=/android-2.3-RC1 SDCARD=/data/sdcard.img UVESA_MODE=320x480 DPI=160

Reboot

How do I dispatch_sync, dispatch_async, dispatch_after, etc in Swift 3, Swift 4, and beyond?

Since the beginning, Swift has provided some facilities for making ObjC and C more Swifty, adding more with each version. Now, in Swift 3, the new "import as member" feature lets frameworks with certain styles of C API -- where you have a data type that works sort of like a class, and a bunch of global functions to work with it -- act more like Swift-native APIs. The data types import as Swift classes, their related global functions import as methods and properties on those classes, and some related things like sets of constants can become subtypes where appropriate.

In Xcode 8 / Swift 3 beta, Apple has applied this feature (along with a few others) to make the Dispatch framework much more Swifty. (And Core Graphics, too.) If you've been following the Swift open-source efforts, this isn't news, but now is the first time it's part of Xcode.

Your first step on moving any project to Swift 3 should be to open it in Xcode 8 and choose Edit > Convert > To Current Swift Syntax... in the menu. This will apply (with your review and approval) all of the changes at once needed for all the renamed APIs and other changes. (Often, a line of code is affected by more than one of these changes at once, so responding to error fix-its individually might not handle everything right.)

The result is that the common pattern for bouncing work to the background and back now looks like this:

// Move to a background thread to do some long running work
DispatchQueue.global(qos: .userInitiated).async {
    let image = self.loadOrGenerateAnImage()
    // Bounce back to the main thread to update the UI
    DispatchQueue.main.async {
        self.imageView.image = image
    }
}

Note we're using .userInitiated instead of one of the old DISPATCH_QUEUE_PRIORITY constants. Quality of Service (QoS) specifiers were introduced in OS X 10.10 / iOS 8.0, providing a clearer way for the system to prioritize work and deprecating the old priority specifiers. See Apple's docs on background work and energy efficiency for details.

By the way, if you're keeping your own queues to organize work, the way to get one now looks like this (notice that DispatchQueueAttributes is an OptionSet, so you use collection-style literals to combine options):

class Foo { 
    let queue = DispatchQueue(label: "com.example.my-serial-queue",
                           attributes: [.serial, .qosUtility])
    func doStuff() {
        queue.async {
            print("Hello World")
        }
    }
}

Using dispatch_after to do work later? That's a method on queues, too, and it takes a DispatchTime, which has operators for various numeric types so you can just add whole or fractional seconds:

DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { // in half a second...
    print("Are we there yet?")
}

You can find your way around the new Dispatch API by opening its interface in Xcode 8 -- use Open Quickly to find the Dispatch module, or put a symbol (like DispatchQueue) in your Swift project/playground and command-click it, then brouse around the module from there. (You can find the Swift Dispatch API in Apple's spiffy new API Reference website and in-Xcode doc viewer, but it looks like the doc content from the C version hasn't moved into it just yet.)

See the Migration Guide for more tips.

JSON to PHP Array using file_get_contents

You JSON is not a valid string as P. Galbraith has told you above.

and here is the solution for it.

<?php 
$json_url = "http://api.testmagazine.com/test.php?type=menu";
$json = file_get_contents($json_url);
$json=str_replace('},

]',"}

]",$json);
$data = json_decode($json);

echo "<pre>";
print_r($data);
echo "</pre>";
?>

Use this code it will work for you.

How to duplicate a git repository? (without forking)

If you are copying to GitHub, you may use the GitHub Importer to do that for you. The original repo can even be from other version control systems.

How do I select elements of an array given condition?

Your expression works if you add parentheses:

>>> y[(1 < x) & (x < 5)]
array(['o', 'o', 'a'], 
      dtype='|S1')

Trying to use fetch and pass in mode: no-cors

The simple solution: Add the following to the very top of the php file you are requesting the data from.

header("Access-Control-Allow-Origin: *");

Check if the file exists using VBA

just get rid of those speech marks

Sub test()

Dim thesentence As String

thesentence = InputBox("Type the filename with full extension", "Raw Data File")

Range("A1").Value = thesentence

If Dir(thesentence) <> "" Then
    MsgBox "File exists."
Else
    MsgBox "File doesn't exist."
End If

End Sub

This is the one I like:

Option Explicit

Enum IsFileOpenStatus
    ExistsAndClosedOrReadOnly = 0
    ExistsAndOpenSoBlocked = 1
    NotExists = 2
End Enum


Function IsFileReadOnlyOpen(FileName As String) As IsFileOpenStatus

With New FileSystemObject
    If Not .FileExists(FileName) Then
        IsFileReadOnlyOpen = 2  '  NotExists = 2
        Exit Function 'Or not - I don't know if you want to create the file or exit in that case.
    End If
End With

Dim iFilenum As Long
Dim iErr As Long
On Error Resume Next
    iFilenum = FreeFile()
    Open FileName For Input Lock Read As #iFilenum
    Close iFilenum
    iErr = Err
On Error GoTo 0

Select Case iErr
    Case 0: IsFileReadOnlyOpen = 0 'ExistsAndClosedOrReadOnly = 0
    Case 70: IsFileReadOnlyOpen = 1 'ExistsAndOpenSoBlocked = 1
    Case Else: IsFileReadOnlyOpen = 1 'Error iErr
End Select

End Function    'IsFileReadOnlyOpen

Detect if value is number in MySQL

Returns numeric rows

I found the solution with following query and works for me:

SELECT * FROM myTable WHERE col1 > 0;

This query return rows having only greater than zero number column that col1

Returns non numeric rows

if you want to check column not numeric try this one with the trick (!col1 > 0):

SELECT * FROM myTable WHERE !col1 > 0;

How to run a .awk file?

If you put #!/bin/awk -f on the first line of your AWK script it is easier. Plus editors like Vim and ... will recognize the file as an AWK script and you can colorize. :)

#!/bin/awk -f
BEGIN {}  # Begin section
{}        # Loop section
END{}     # End section

Change the file to be executable by running:

chmod ugo+x ./awk-script

and you can then call your AWK script like this:

`$ echo "something" | ./awk-script`

XmlSerializer giving FileNotFoundException at constructor

I was getting the same error, and it was due to the type I was trying to deserialize not having a default parameterless constructor. I added a constructor, and it started working.

Android: making a fullscreen application

I recently had the exact same issue and benefitted from the following post as well (in addition to Rohit5k2's solution above):

https://bsgconsultancy.wordpress.com/2015/09/13/convert-any-website-into-android-application-by-using-android-studio/

In Step 3, MainActivity extends Activity instead of ActionBarActivity (as Rohit5k2 mentioned). Putting the NoTitleBar and Fullscreen theme elements into the correct places in the AndroidManifest.xml file is also very important (take a look at Step 4).

How to fix Invalid AES key length?

I was facing the same issue then i made my key 16 byte and it's working properly now. Create your key exactly 16 byte. It will surely work.

How to list all Git tags?

And here is how you find the remote tags:

git ls-remote --tags origin

How to do a join in linq to sql with method syntax?

To add on to the other answers here, if you would like to create a new object of a third different type with a where clause (e.g. one that is not your Entity Framework object) you can do this:

public IEnumerable<ThirdNonEntityClass> demoMethod(IEnumerable<int> property1Values)
{
    using(var entityFrameworkObjectContext = new EntityFrameworkObjectContext )
    {
        var result = entityFrameworkObjectContext.SomeClass
            .Join(entityFrameworkObjectContext.SomeOtherClass,
                sc => sc.property1,
                soc => soc.property2,
                (sc, soc) => new {sc, soc})
            .Where(s => propertyValues.Any(pvals => pvals == es.sc.property1)
            .Select(s => new ThirdNonEntityClass 
            {
                dataValue1 = s.sc.dataValueA,
                dataValue2 = s.soc.dataValueB
            })
            .ToList();
    }

    return result;

}    

Pay special attention to the intermediate object that is created in the Where and Select clauses.

Note that here we also look for any joined objects that have a property1 that matches one of the ones in the input list.

I know this is a bit more complex than what the original asker was looking for, but hopefully it will help someone.

How to make <input type="file"/> accept only these types?

for powerpoint and pdf files:

<html>
<input type="file" placeholder="Do you have a .ppt?" name="pptfile" id="pptfile" accept="application/pdf,application/vnd.ms-powerpoint,application/vnd.openxmlformats-officedocument.presentationml.slideshow,application/vnd.openxmlformats-officedocument.presentationml.presentation"/>
</html>

Methods vs Constructors in Java

Other instructors and teaching assistants occasionally tell me that constructors are specialized methods. I always argue that in Java constructors are NOT specialized methods.

If constructors were methods at all, I would expect them to have the same abilities as methods. That they would at least be similar in more ways than they are different.

How are constructors different than methods? Let me count the ways...

  1. Constructors must be invoked with the new operator while methods may not be invoked with the new operator. Related: Constructors may not be called by name while methods must be called by name.

  2. Constructors may not have a return type while methods must have a return type.

  3. If a method has the same name as the class, it must have a return type. Otherwise, it is a constructor. The fact that you can have two MyClass() signatures in the same class definition which are treated differently should convince all that constructors and methods are different entities:

    public class MyClass {
       public MyClass() { }                                   // constructor
       public String MyClass() { return "MyClass() method"; } // method
    }
    
  4. Constructors may initialize instance constants while methods may not.

  5. Public and protected constructors are not inherited while public and protected methods are inherited.

  6. Constructors may call the constructors of the super class or same class while methods may not call either super() or this().

So, what is similar about methods and constructors?

  1. They both have parameter lists.

  2. They both have blocks of code that will be executed when that block is either called directly (methods) or invoked via new (constructors).

As for constructors and methods having the same visibility modifiers... fields and methods have more visibility modifiers in common.

  1. Constructors may be: private, protected, public.

  2. Methods may be: private, protected, public, abstract, static, final, synchronized, native, strictfp.

  3. Data fields may be: private, protected, public, static, final, transient, volatile.

In Conclusion

In Java, the form and function of constructors is significantly different than for methods. Thus, calling them specialized methods actually makes it harder for new programmers to learn the differences. They are much more different than similar and learning them as different entities is critical in Java.

I do recognize that Java is different than other languages in this regard, namely C++, where the concept of specialized methods originates and is supported by the language rules. But, in Java, constructors are not methods at all, much less specialized methods.

Even javadoc recognizes the differences between constructors and methods outweigh the similarities; and provides a separate section for constructors.

The project cannot be built until the build path errors are resolved.

I was getting an additional warning

The compiler compliance specified is 1.6 but a JRE 1.8 is used

Resolving this warning make the error also go away. The steps are as follows:

I right-clicked on it, then clicked on Quick Fix. From the dialog that opened I selected Open the Compiler Compliance property page, and clicked the Finish button.

(This is same as Java Compiler section.)

In this dialog I found the Compiler compliance level drop down and changed 1.6 to 1.8, and clicked on Apply and close.

I got a message box Compiler Settings Changed which asked if I wanted to Build the project now?. I clicked on Yes.

The build path error went away.

How can INSERT INTO a table 300 times within a loop in SQL?

I would prevent loops in general if i can, set approaches are much more efficient:

INSERT INTO tblFoo
  SELECT TOP (300) n = ROW_NUMBER()OVER (ORDER BY [object_id]) 
  FROM sys.all_objects ORDER BY n;

Demo

Generate a set or sequence without loops

Get the cartesian product of a series of lists?

itertools.product

Available from Python 2.6.

import itertools

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

Which is the same as,

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

Cutting the videos based on start and end time using ffmpeg

    ffmpeg -i movie.mp4 -vf trim=3:8 cut.mp4

Drop everything except from second 3 to second 8.

How do I keep jQuery UI Accordion collapsed by default?

Add the active: false option (documentation)..

$("#accordion").accordion({ header: "h3", collapsible: true, active: false });

How do I execute a file in Cygwin?

To execute a file in the current directory, the syntax to use is: ./foo

As mentioned by allain, ./a.exe is the correct way to execute a.exe in the working directory using Cygwin.

Note: You may wish to use the -o parameter to cc to specify your own output filename. An example of this would be: cc helloworld.c -o helloworld.exe.

How to check if a class inherits another class without instantiating it?

Try this

typeof(IFoo).IsAssignableFrom(typeof(BarClass));

This will tell you whether BarClass(Derived) implements IFoo(SomeType) or not

image size (drawable-hdpi/ldpi/mdpi/xhdpi)

low dpi is 0.75x dimensions of medium dpi

high dpi is 1.5x dimensions of medium dpi

extra high dpi is 2x dimensinons of medium dpi

It's a good practice to make all the images in vector based format so you can resize them easily using a vector design software like Illustrator etc..

How to access model hasMany Relation with where condition?

I think that this is the correct way:

class Game extends Eloquent {
    // many more stuff here

    // relation without any constraints ...works fine 
    public function videos() {
        return $this->hasMany('Video');
    }

    // results in a "problem", se examples below
    public function available_videos() {
        return $this->videos()->where('available','=', 1);
    }
}

And then you'll have to

$game = Game::find(1);
var_dump( $game->available_videos()->get() );

How to: Create trigger for auto update modified date with SQL Server 2008

My approach:

  • define a default constraint on the ModDate column with a value of GETDATE() - this handles the INSERT case

  • have a AFTER UPDATE trigger to update the ModDate column

Something like:

CREATE TRIGGER trg_UpdateTimeEntry
ON dbo.TimeEntry
AFTER UPDATE
AS
    UPDATE dbo.TimeEntry
    SET ModDate = GETDATE()
    WHERE ID IN (SELECT DISTINCT ID FROM Inserted)

how to find seconds since 1970 in java

The difference you see is most likely because you don't zero the hour, minute, second and milliseconds fields of your Calendar instances: Calendar.getInstance() gives you the current date and time, just like new Date() or System.currentTimeMillis().

Note that the month field of Calendar is zero-based, i.e. January is 0, not 1.

Also, don't prefix numbers with zero, this might look nice and it even works till you reach 8: 08 isn't a valid numeral in Java. Prefixing numerals with zero makes the compiler assume you're defining them as octal numerals which only works up to 07 (for single digits).

Just drop calendar1 completely (1970-01-01 00:00:00'000 is the begin of the epoch, i.e. zero anyway) and do this:

public long returnSeconds(int year, int month, int date) {
    final Calendar cal = Calendar.getInstance();
    cal.set(year, month, date, 0, 0, 0);
    cal.set(Calendar.MILLISECOND, 0);
    return cal.getTimeInMillis() / 1000;
}

Creating a copy of an object in C#

There is no built-in way. You can have MyClass implement the IClonable interface (but it is sort of deprecated) or just write your own Copy/Clone method. In either case you will have to write some code.

For big objects you could consider Serialization + Deserialization (through a MemoryStream), just to reuse existing code.

Whatever the method, think carefully about what "a copy" means exactly. How deep should it go, are there Id fields to be excepted etc.

Is there a CSS selector by class prefix?

CSS Attribute selectors will allow you to check attributes for a string. (in this case - a class-name)

https://developer.mozilla.org/en-US/docs/Web/CSS/Attribute_selectors

(looks like it's actually at 'recommendation' status for 2.1 and 3)


Here's an outline of how I *think it works:

  • [ ] : is the container for complex selectors if you will...
  • class : 'class' is the attribute you are looking at in this case.
  • * : modifier(if any): in this case - "wildcard" indicates you're looking for ANY match.
  • test- : the value (assuming there is one) of the attribute - that contains the string "test-" (which could be anything)

So, for example:

[class*='test-'] {
  color: red;
}

You could be more specific if you have good reason, with the element too

ul[class*='test-'] > li { ... }

I've tried to find edge cases, but I see no need to use a combination of ^ and * - as * gets everything...

example: http://codepen.io/sheriffderek/pen/MaaBwp

http://caniuse.com/#feat=css-sel2

Everything above IE6 will happily obey. : )

note that:

[class] { ... }

Will select anything with a class...

How to select the nth row in a SQL database table?

1 small change: n-1 instead of n.

select *
from thetable
limit n-1, 1

C++ Convert string (or char*) to wstring (or wchar_t*)

int StringToWString(std::wstring &ws, const std::string &s)
{
    std::wstring wsTmp(s.begin(), s.end());

    ws = wsTmp;

    return 0;
}

How do I find files with a path length greater than 260 characters in Windows?

I created the Path Length Checker tool for this purpose, which is a nice, free GUI app that you can use to see the path lengths of all files and directories in a given directory.

I've also written and blogged about a simple PowerShell script for getting file and directory lengths. It will output the length and path to a file, and optionally write it to the console as well. It doesn't limit to displaying files that are only over a certain length (an easy modification to make), but displays them descending by length, so it's still super easy to see which paths are over your threshold. Here it is:

$pathToScan = "C:\Some Folder"  # The path to scan and the the lengths for (sub-directories will be scanned as well).
$outputFilePath = "C:\temp\PathLengths.txt" # This must be a file in a directory that exists and does not require admin rights to write to.
$writeToConsoleAsWell = $true   # Writing to the console will be much slower.

# Open a new file stream (nice and fast) and write all the paths and their lengths to it.
$outputFileDirectory = Split-Path $outputFilePath -Parent
if (!(Test-Path $outputFileDirectory)) { New-Item $outputFileDirectory -ItemType Directory }
$stream = New-Object System.IO.StreamWriter($outputFilePath, $false)
Get-ChildItem -Path $pathToScan -Recurse -Force | Select-Object -Property FullName, @{Name="FullNameLength";Expression={($_.FullName.Length)}} | Sort-Object -Property FullNameLength -Descending | ForEach-Object {
    $filePath = $_.FullName
    $length = $_.FullNameLength
    $string = "$length : $filePath"

    # Write to the Console.
    if ($writeToConsoleAsWell) { Write-Host $string }

    #Write to the file.
    $stream.WriteLine($string)
}
$stream.Close()

IndentationError: unexpected unindent WHY?

@MaxPython The answer above is missing ":"

try:
   #do something
except:
  # print 'error/exception'

def printError(e): print e

Pivoting rows into columns dynamically in Oracle

First of all, dynamically pivot using pivot xml again needs to be parsed. We have another way of doing this by storing the column names in a variable and passing them in the dynamic sql as below.

Consider we have a table like below.

enter image description here

If we need to show the values in the column YR as column names and the values in those columns from QTY, then we can use the below code.

declare
  sqlqry clob;
  cols clob;
begin
  select listagg('''' || YR || ''' as "' || YR || '"', ',') within group (order by YR)
  into   cols
  from   (select distinct YR from EMPLOYEE);


  sqlqry :=
  '      
  select * from
  (
      select *
      from EMPLOYEE
  )
  pivot
  (
    MIN(QTY) for YR in (' || cols  || ')
  )';

  execute immediate sqlqry;
end;
/

RESULT

enter image description here

Error in plot.window(...) : need finite 'xlim' values

I had the same problem. I solve it when I convert string to factor. In your case, check the class of variable and check if they are numeric and 'train and test' should be factor.

How to verify an XPath expression in Chrome Developers tool or Firefox's Firebug?

Chrome

This can be achieved by three different approaches (see my blog article here for more details):

  • Search in Elements panel like below
  • Execute $x() and $$() in Console panel, as shown in Lawrence's answer
  • Third party extensions (not really necessary in most of the cases, could be an overkill)

Here is how you search XPath in Elements panel:

  1. Press F12 to open Chrome Developer Tool
  2. In "Elements" panel, press Ctrl+F
  3. In the search box, type in XPath or CSS Selector, if elements are found, they will be highlighted in yellow.

enter image description here

Firefox (since version 75)

Since FF 75 it's possible to use raw xpath query without evaluation xpath expressions, see documentation for more info.

Firefox (prior version 75)

  1. Either select "Web Console" from the Web Developer submenu in the Firefox Menu (or Tools menu if you display the menu bar or are on Mac OS X)
    or press the Ctrl+Shift+K (Command+Option+K on OS X) keyboard shortcut.
  2. In the command line at the bottom use the following:

    • $(): Returns the first element that matches. Equivalent to document.querySelector() or calls the $ function in the page, if it exists.

    • $$(): Returns an array of DOM nodes that match. This is like for document.querySelectorAll(), but returns an array instead of a NodeList.

    • $x(): Evaluates an XPath expression and returns an array of matching nodes.


Firefox (prior version 49)

  1. Install Firebug
  2. Install Firepath
  3. Press F12 to open Firebug
  4. Switch to FirePath panel
  5. In dropdown, select XPathor CSS
  6. Type in to locate

enter image description here

Negation in Python

The negation operator in Python is not. Therefore just replace your ! with not.

For your example, do this:

if not os.path.exists("/usr/share/sounds/blues") :
    proc = subprocess.Popen(["mkdir", "/usr/share/sounds/blues"])
    proc.wait()

For your specific example (as Neil said in the comments), you don't have to use the subprocess module, you can simply use os.mkdir() to get the result you need, with added exception handling goodness.

Example:

blues_sounds_path = "/usr/share/sounds/blues"
if not os.path.exists(blues_sounds_path):
    try:
        os.mkdir(blues_sounds_path)
    except OSError:
        # Handle the case where the directory could not be created.

Read a Csv file with powershell and capture corresponding data

What you should be looking at is Import-Csv

Once you import the CSV you can use the column header as the variable.

Example CSV:

Name  | Phone Number | Email
Elvis | 867.5309     | [email protected]
Sammy | 555.1234     | [email protected]

Now we will import the CSV, and loop through the list to add to an array. We can then compare the value input to the array:

$Name = @()
$Phone = @()

Import-Csv H:\Programs\scripts\SomeText.csv |`
    ForEach-Object {
        $Name += $_.Name
        $Phone += $_."Phone Number"
    }

$inputNumber = Read-Host -Prompt "Phone Number"

if ($Phone -contains $inputNumber)
    {
    Write-Host "Customer Exists!"
    $Where = [array]::IndexOf($Phone, $inputNumber)
    Write-Host "Customer Name: " $Name[$Where]
    }

And here is the output:

I Found Sammy

How can I check for IsPostBack in JavaScript?

Create a global variable in and apply the value

<script>
       var isPostBack = <%=Convert.ToString(Page.IsPostBack).ToLower()%>;
</script>

Then you can reference it from elsewhere

How to add a constant column in a Spark DataFrame?

As the other answers have described, lit and typedLit are how to add constant columns to DataFrames. lit is an important Spark function that you will use frequently, but not for adding constant columns to DataFrames.

You'll commonly be using lit to create org.apache.spark.sql.Column objects because that's the column type required by most of the org.apache.spark.sql.functions.

Suppose you have a DataFrame with a some_date DateType column and would like to add a column with the days between December 31, 2020 and some_date.

Here's your DataFrame:

+----------+
| some_date|
+----------+
|2020-09-23|
|2020-01-05|
|2020-04-12|
+----------+

Here's how to calculate the days till the year end:

val diff = datediff(lit(Date.valueOf("2020-12-31")), col("some_date"))
df
  .withColumn("days_till_yearend", diff)
  .show()
+----------+-----------------+
| some_date|days_till_yearend|
+----------+-----------------+
|2020-09-23|               99|
|2020-01-05|              361|
|2020-04-12|              263|
+----------+-----------------+

You could also use lit to create a year_end column and compute the days_till_yearend like so:

import java.sql.Date

df
  .withColumn("yearend", lit(Date.valueOf("2020-12-31")))
  .withColumn("days_till_yearend", datediff(col("yearend"), col("some_date")))
  .show()
+----------+----------+-----------------+
| some_date|   yearend|days_till_yearend|
+----------+----------+-----------------+
|2020-09-23|2020-12-31|               99|
|2020-01-05|2020-12-31|              361|
|2020-04-12|2020-12-31|              263|
+----------+----------+-----------------+

Most of the time, you don't need to use lit to append a constant column to a DataFrame. You just need to use lit to convert a Scala type to a org.apache.spark.sql.Column object because that's what's required by the function.

See the datediff function signature:

enter image description here

As you can see, datediff requires two Column arguments.

What does the [Flags] Enum Attribute mean in C#?

When working with flags I often declare additional None and All items. These are helpful to check whether all flags are set or no flag is set.

[Flags] 
enum SuitsFlags { 

    None =     0,

    Spades =   1 << 0, 
    Clubs =    1 << 1, 
    Diamonds = 1 << 2, 
    Hearts =   1 << 3,

    All =      ~(~0 << 4)

}

Usage:

Spades | Clubs | Diamonds | Hearts == All  // true
Spades & Clubs == None  // true

 
Update 2019-10:

Since C# 7.0 you can use binary literals, which are probably more intuitive to read:

[Flags] 
enum SuitsFlags { 

    None =     0b0000,

    Spades =   0b0001, 
    Clubs =    0b0010, 
    Diamonds = 0b0100, 
    Hearts =   0b1000,

    All =      0b1111

}

Assembly - JG/JNLE/JL/JNGE after CMP

When you do a cmp a,b, the flags are set as if you had calculated a - b.

Then the jmp-type instructions check those flags to see if the jump should be made.

In other words, the first block of code you have (with my comments added):

cmp al,dl     ; set flags based on the comparison
jg label1     ; then jump based on the flags

would jump to label1 if and only if al was greater than dl.

You're probably better off thinking of it as al > dl but the two choices you have there are mathematically equivalent:

al > dl
al - dl > dl - dl (subtract dl from both sides)
al - dl > 0       (cancel the terms on the right hand side)

You need to be careful when using jg inasmuch as it assumes your values were signed. So, if you compare the bytes 101 (101 in two's complement) with 200 (-56 in two's complement), the former will actually be greater. If that's not what was desired, you should use the equivalent unsigned comparison.

See here for more detail on jump selection, reproduced below for completeness. First the ones where signed-ness is not appropriate:

+--------+------------------------------+-------------+--------------------+
|Instr   | Description                  | signed-ness | Flags              |
+--------+------------------------------+-------------+--------------------+
| JO     | Jump if overflow             |             | OF = 1             |
+--------+------------------------------+-------------+--------------------+
| JNO    | Jump if not overflow         |             | OF = 0             |
+--------+------------------------------+-------------+--------------------+
| JS     | Jump if sign                 |             | SF = 1             |
+--------+------------------------------+-------------+--------------------+
| JNS    | Jump if not sign             |             | SF = 0             |
+--------+------------------------------+-------------+--------------------+
| JE/    | Jump if equal                |             | ZF = 1             |
| JZ     | Jump if zero                 |             |                    |
+--------+------------------------------+-------------+--------------------+
| JNE/   | Jump if not equal            |             | ZF = 0             |
| JNZ    | Jump if not zero             |             |                    |
+--------+------------------------------+-------------+--------------------+
| JP/    | Jump if parity               |             | PF = 1             |
| JPE    | Jump if parity even          |             |                    |
+--------+------------------------------+-------------+--------------------+
| JNP/   | Jump if no parity            |             | PF = 0             |
| JPO    | Jump if parity odd           |             |                    |
+--------+------------------------------+-------------+--------------------+
| JCXZ/  | Jump if CX is zero           |             | CX = 0             |
| JECXZ  | Jump if ECX is zero          |             | ECX = 0            |
+--------+------------------------------+-------------+--------------------+

Then the unsigned ones:

+--------+------------------------------+-------------+--------------------+
|Instr   | Description                  | signed-ness | Flags              |
+--------+------------------------------+-------------+--------------------+
| JB/    | Jump if below                | unsigned    | CF = 1             |
| JNAE/  | Jump if not above or equal   |             |                    |
| JC     | Jump if carry                |             |                    |
+--------+------------------------------+-------------+--------------------+
| JNB/   | Jump if not below            | unsigned    | CF = 0             |
| JAE/   | Jump if above or equal       |             |                    |
| JNC    | Jump if not carry            |             |                    |
+--------+------------------------------+-------------+--------------------+
| JBE/   | Jump if below or equal       | unsigned    | CF = 1 or ZF = 1   |
| JNA    | Jump if not above            |             |                    |
+--------+------------------------------+-------------+--------------------+
| JA/    | Jump if above                | unsigned    | CF = 0 and ZF = 0  |
| JNBE   | Jump if not below or equal   |             |                    |
+--------+------------------------------+-------------+--------------------+

And, finally, the signed ones:

+--------+------------------------------+-------------+--------------------+
|Instr   | Description                  | signed-ness | Flags              |
+--------+------------------------------+-------------+--------------------+
| JL/    | Jump if less                 | signed      | SF <> OF           |
| JNGE   | Jump if not greater or equal |             |                    |
+--------+------------------------------+-------------+--------------------+
| JGE/   | Jump if greater or equal     | signed      | SF = OF            |
| JNL    | Jump if not less             |             |                    |
+--------+------------------------------+-------------+--------------------+
| JLE/   | Jump if less or equal        | signed      | ZF = 1 or SF <> OF |
| JNG    | Jump if not greater          |             |                    |
+--------+------------------------------+-------------+--------------------+
| JG/    | Jump if greater              | signed      | ZF = 0 and SF = OF |
| JNLE   | Jump if not less or equal    |             |                    |
+--------+------------------------------+-------------+--------------------+

How to send a HTTP OPTIONS request from the command line?

The curl installed by default in Debian supports HTTPS since a great while back. (a long time ago there were two separate packages, one with and one without SSL but that's not the case anymore)

OPTIONS /path

You can send an OPTIONS request with curl like this:

curl -i -X OPTIONS http://example.org/path

You may also use -v instead of -i to see more output.

OPTIONS *

To send a plain * (instead of the path, see RFC 7231) with the OPTIONS method, you need curl 7.55.0 or later as then you can run a command line like:

curl -i --request-target "*" -X OPTIONS http://example.org

Fatal error: Call to undefined function pg_connect()

You need to install the php-pgsql package or whatever it's called for your platform. Which I don't think you said by the way.

On Ubuntu and Debian:

sudo apt-get install php5-pgsql

How to remove empty lines with or without whitespace in Python

I use this solution to delete empty lines and join everything together as one line:

match_p = re.sub(r'\s{2}', '', my_txt) # my_txt is text above

Set focus on <input> element

This directive will instantly focus and select any text in the element as soon as it's displayed. This might require a setTimeout for some cases, it has not been tested much.

import { Directive, ElementRef, OnInit } from '@angular/core';

@Directive({
  selector: '[appPrefixFocusAndSelect]',
})
export class FocusOnShowDirective implements OnInit {

  constructor(private el: ElementRef) {
    if (!el.nativeElement['focus']) {
      throw new Error('Element does not accept focus.');
    }
  }

  ngOnInit(): void {
    const input: HTMLInputElement = this.el.nativeElement as HTMLInputElement;
    input.focus();
    input.select();
  }
}

And in the HTML:

 <mat-form-field>
     <input matInput type="text" appPrefixFocusAndSelect [value]="'etc'">
 </mat-form-field>

Make 2 functions run at the same time

test using APscheduler:

from apscheduler.schedulers.background import BackgroundScheduler
import datetime

dt = datetime.datetime
Future = dt.now() + datetime.timedelta(milliseconds=2550)  # 2.55 seconds from now testing start accuracy

def myjob1():
    print('started job 1: ' + str(dt.now())[:-3])  # timed to millisecond because thats where it varies
    time.sleep(5)
    print('job 1 half at: ' + str(dt.now())[:-3])
    time.sleep(5)
    print('job 1 done at: ' + str(dt.now())[:-3])
def myjob2():
    print('started job 2: ' + str(dt.now())[:-3])
    time.sleep(5)
    print('job 2 half at: ' + str(dt.now())[:-3])
    time.sleep(5)
    print('job 2 done at: ' + str(dt.now())[:-3])

print(' current time: ' + str(dt.now())[:-3])
print('  do job 1 at: ' + str(Future)[:-3] + ''' 
  do job 2 at: ''' + str(Future)[:-3])
sched.add_job(myjob1, 'date', run_date=Future)
sched.add_job(myjob2, 'date', run_date=Future)

i got these results. which proves they are running at the same time.

 current time: 2020-12-15 01:54:26.526
  do job 1 at: 2020-12-15 01:54:29.072  # i figure these both say .072 because its 1 line of print code
  do job 2 at: 2020-12-15 01:54:29.072
started job 2: 2020-12-15 01:54:29.075  # notice job 2 started before job 1, but code calls job 1 first.
started job 1: 2020-12-15 01:54:29.076  
job 2 half at: 2020-12-15 01:54:34.077  # halfway point on each job completed same time accurate to the millisecond
job 1 half at: 2020-12-15 01:54:34.077
job 1 done at: 2020-12-15 01:54:39.078  # job 1 finished first. making it .004 seconds faster.
job 2 done at: 2020-12-15 01:54:39.091  # job 2 was .002 seconds faster the second test

How can I make my own event in C#?

I have a full discussion of events and delegates in my events article. For the simplest kind of event, you can just declare a public event and the compiler will create both an event and a field to keep track of subscribers:

public event EventHandler Foo;

If you need more complicated subscription/unsubscription logic, you can do that explicitly:

public event EventHandler Foo
{
    add
    {
        // Subscription logic here
    }
    remove
    {
        // Unsubscription logic here
    }
}

Pretty Printing a pandas dataframe

Following up on Mark's answer, if you're not using Jupyter for some reason, e.g. you want to do some quick testing on the console, you can use the DataFrame.to_string method, which works from -- at least -- Pandas 0.12 (2014) onwards.

import pandas as pd

matrix = [(1, 23, 45), (789, 1, 23), (45, 678, 90)]
df = pd.DataFrame(matrix, columns=list('abc'))
print(df.to_string())

#  outputs:
#       a    b   c
#  0    1   23  45
#  1  789    1  23
#  2   45  678  90

Returning unique_ptr from functions

One thing that i didn't see in other answers is To clarify another answers that there is a difference between returning std::unique_ptr that has been created within a function, and one that has been given to that function.

The example could be like this:

class Test
{int i;};
std::unique_ptr<Test> foo1()
{
    std::unique_ptr<Test> res(new Test);
    return res;
}
std::unique_ptr<Test> foo2(std::unique_ptr<Test>&& t)
{
    // return t;  // this will produce an error!
    return std::move(t);
}

//...
auto test1=foo1();
auto test2=foo2(std::unique_ptr<Test>(new Test));

Why should I use core.autocrlf=true in Git?

For me.

Edit .gitattributes file.

add

*.dll binary

Then everything goes well.

Remove by _id in MongoDB console

I've just bumped into this myself and this variation worked for me:

db.foo.remove({**_id**: new ObjectId("4f872685a64eed5a980ca536")})

Java: How to read a text file

Look at this example, and try to do your own:

import java.io.*;

public class ReadFile {

    public static void main(String[] args){
        String string = "";
        String file = "textFile.txt";

        // Reading
        try{
            InputStream ips = new FileInputStream(file);
            InputStreamReader ipsr = new InputStreamReader(ips);
            BufferedReader br = new BufferedReader(ipsr);
            String line;
            while ((line = br.readLine()) != null){
                System.out.println(line);
                string += line + "\n";
            }
            br.close();
        }
        catch (Exception e){
            System.out.println(e.toString());
        }

        // Writing
        try {
            FileWriter fw = new FileWriter (file);
            BufferedWriter bw = new BufferedWriter (fw);
            PrintWriter fileOut = new PrintWriter (bw);
                fileOut.println (string+"\n test of read and write !!");
            fileOut.close();
            System.out.println("the file " + file + " is created!");
        }
        catch (Exception e){
            System.out.println(e.toString());
        }
    }
}

PHP reindex array?

$myarray = array_values($myarray);

array_values

Using group by on multiple columns

Here I am going to explain not only the GROUP clause use, but also the Aggregate functions use.

The GROUP BY clause is used in conjunction with the aggregate functions to group the result-set by one or more columns. e.g.:

-- GROUP BY with one parameter:
SELECT column_name, AGGREGATE_FUNCTION(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

-- GROUP BY with two parameters:
SELECT
    column_name1,
    column_name2,
    AGGREGATE_FUNCTION(column_name3)
FROM
    table_name
GROUP BY
    column_name1,
    column_name2;

Remember this order:

  1. SELECT (is used to select data from a database)

  2. FROM (clause is used to list the tables)

  3. WHERE (clause is used to filter records)

  4. GROUP BY (clause can be used in a SELECT statement to collect data across multiple records and group the results by one or more columns)

  5. HAVING (clause is used in combination with the GROUP BY clause to restrict the groups of returned rows to only those whose the condition is TRUE)

  6. ORDER BY (keyword is used to sort the result-set)

You can use all of these if you are using aggregate functions, and this is the order that they must be set, otherwise you can get an error.

Aggregate Functions are:

MIN() returns the smallest value in a given column

MAX() returns the maximum value in a given column.

SUM() returns the sum of the numeric values in a given column

AVG() returns the average value of a given column

COUNT() returns the total number of values in a given column

COUNT(*) returns the number of rows in a table

SQL script examples about using aggregate functions:

Let's say we need to find the sale orders whose total sale is greater than $950. We combine the HAVING clause and the GROUP BY clause to accomplish this:

SELECT 
    orderId, SUM(unitPrice * qty) Total
FROM
    OrderDetails
GROUP BY orderId
HAVING Total > 950;

Counting all orders and grouping them customerID and sorting the result ascendant. We combine the COUNT function and the GROUP BY, ORDER BY clauses and ASC:

SELECT 
    customerId, COUNT(*)
FROM
    Orders
GROUP BY customerId
ORDER BY COUNT(*) ASC;

Retrieve the category that has an average Unit Price greater than $10, using AVG function combine with GROUP BY and HAVING clauses:

SELECT 
    categoryName, AVG(unitPrice)
FROM
    Products p
INNER JOIN
    Categories c ON c.categoryId = p.categoryId
GROUP BY categoryName
HAVING AVG(unitPrice) > 10;

Getting the less expensive product by each category, using the MIN function in a subquery:

SELECT categoryId,
       productId,
       productName,
       unitPrice
FROM Products p1
WHERE unitPrice = (
                SELECT MIN(unitPrice)
                FROM Products p2
                WHERE p2.categoryId = p1.categoryId)

The following statement groups rows with the same values in both categoryId and productId columns:

SELECT 
    categoryId, categoryName, productId, SUM(unitPrice)
FROM
    Products p
INNER JOIN
    Categories c ON c.categoryId = p.categoryId
GROUP BY categoryId, productId

MySQL TEXT vs BLOB vs CLOB

It's worth to mention that CLOB / BLOB data types and their sizes are supported by MySQL 5.0+, so you can choose the proper data type for your need.

http://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html

Data Type   Date Type   Storage Required
(CLOB)      (BLOB)

TINYTEXT    TINYBLOB    L + 1 bytes, where L < 2**8  (255)
TEXT        BLOB        L + 2 bytes, where L < 2**16 (64 K)
MEDIUMTEXT  MEDIUMBLOB  L + 3 bytes, where L < 2**24 (16 MB)
LONGTEXT    LONGBLOB    L + 4 bytes, where L < 2**32 (4 GB)

where L stands for the byte length of a string

Convert Numeric value to Varchar

i think it should be

select convert(varchar(10),StandardCost) +'S' from DimProduct where ProductKey = 212

or

select cast(StandardCost as varchar(10)) + 'S' from DimProduct where ProductKey = 212

How to set java_home on Windows 7?

Run Eclipse as Administrator.

That solved my problem. I'm still digging for the logic behind it.

What's the difference between utf8_general_ci and utf8_unicode_ci?

For those people still arriving at this question in 2020 or later, there are newer options that may be better than both of these. For example, utf8mb4_0900_ai_ci.

All these collations are for the UTF-8 character encoding. The differences are in how text is sorted and compared.

_unicode_ci and _general_ci are two different sets of rules for sorting and comparing text according to the way we expect. Newer versions of MySQL introduce new sets of rules, too, such as _0900_ai_ci for equivalent rules based on Unicode 9.0 - and with no equivalent _general_ci variant. People reading this now should probably use one of these newer collations instead of either _unicode_ci or _general_ci. The description of those older collations below is provided for interest only.

MySQL is currently transitioning away from an older, flawed UTF-8 implementation. For now, you need to use utf8mb4 instead of utf8 for the character encoding part, to ensure you are getting the fixed version. The flawed version remains for backward compatibility, though it is being deprecated.

Key differences

  • utf8mb4_unicode_ci is based on the official Unicode rules for universal sorting and comparison, which sorts accurately in a wide range of languages.

  • utf8mb4_general_ci is a simplified set of sorting rules which aims to do as well as it can while taking many short-cuts designed to improve speed. It does not follow the Unicode rules and will result in undesirable sorting or comparison in some situations, such as when using particular languages or characters.

    On modern servers, this performance boost will be all but negligible. It was devised in a time when servers had a tiny fraction of the CPU performance of today's computers.

Benefits of utf8mb4_unicode_ci over utf8mb4_general_ci

utf8mb4_unicode_ci, which uses the Unicode rules for sorting and comparison, employs a fairly complex algorithm for correct sorting in a wide range of languages and when using a wide range of special characters. These rules need to take into account language-specific conventions; not everybody sorts their characters in what we would call 'alphabetical order'.

As far as Latin (ie "European") languages go, there is not much difference between the Unicode sorting and the simplified utf8mb4_general_ci sorting in MySQL, but there are still a few differences:

  • For examples, the Unicode collation sorts "ß" like "ss", and "Œ" like "OE" as people using those characters would normally want, whereas utf8mb4_general_ci sorts them as single characters (presumably like "s" and "e" respectively).

  • Some Unicode characters are defined as ignorable, which means they shouldn't count toward the sort order and the comparison should move on to the next character instead. utf8mb4_unicode_ci handles these properly.

In non-latin languages, such as Asian languages or languages with different alphabets, there may be a lot more differences between Unicode sorting and the simplified utf8mb4_general_ci sorting. The suitability of utf8mb4_general_ci will depend heavily on the language used. For some languages, it'll be quite inadequate.

What should you use?

There is almost certainly no reason to use utf8mb4_general_ci anymore, as we have left behind the point where CPU speed is low enough that the performance difference would be important. Your database will almost certainly be limited by other bottlenecks than this.

In the past, some people recommended to use utf8mb4_general_ci except when accurate sorting was going to be important enough to justify the performance cost. Today, that performance cost has all but disappeared, and developers are treating internationalization more seriously.

There's an argument to be made that if speed is more important to you than accuracy, you may as well not do any sorting at all. It's trivial to make an algorithm faster if you do not need it to be accurate. So, utf8mb4_general_ci is a compromise that's probably not needed for speed reasons and probably also not suitable for accuracy reasons.

One other thing I'll add is that even if you know your application only supports the English language, it may still need to deal with people's names, which can often contain characters used in other languages in which it is just as important to sort correctly. Using the Unicode rules for everything helps add peace of mind that the very smart Unicode people have worked very hard to make sorting work properly.

What the parts mean

Firstly, ci is for case-insensitive sorting and comparison. This means it's suitable for textual data, and case is not important. The other types of collation are cs (case-sensitive) for textual data where case is important, and bin, for where the encoding needs to match, bit for bit, which is suitable for fields which are really encoded binary data (including, for example, Base64). Case-sensitive sorting leads to some weird results and case-sensitive comparison can result in duplicate values differing only in letter case, so case-sensitive collations are falling out of favor for textual data - if case is significant to you, then otherwise ignorable punctuation and so on is probably also significant, and a binary collation might be more appropriate.

Next, unicode or general refers to the specific sorting and comparison rules - in particular, the way text is normalized or compared. There are many different sets of rules for the utf8mb4 character encoding, with unicode and general being two that attempt to work well in all possible languages rather than one specific one. The differences between these two sets of rules are the subject of this answer. Note that unicode uses rules from Unicode 4.0. Recent versions of MySQL add the rulesets unicode_520 using rules from Unicode 5.2, and 0900 (dropping the "unicode_" part) using rules from Unicode 9.0.

And lastly, utf8mb4 is of course the character encoding used internally. In this answer I'm talking only about Unicode based encodings.

How to hide .php extension in .htaccess

The other option for using PHP scripts sans extension is

Options +MultiViews

Or even just following in the directories .htaccess:

DefaultType application/x-httpd-php

The latter allows having all filenames without extension script being treated as PHP scripts. While MultiViews makes the webserver look for alternatives, when just the basename is provided (there's a performance hit with that however).

Access Control Origin Header error using Axios in React Web throwing error in Chrome

As I understand the problem is that request is sent from localhost:3000 to localhost:8080 and browser rejects such requests as CORS. So solution was to create proxy

My solution was :

import proxy from 'http-proxy-middleware'
app.use('/api/**', proxy({ target: "http://localhost:8080" }));

How to start color picker on Mac OS?

You can call up the color picker from any Cocoa application (TextEdit, Mail, Keynote, Pages, etc.) by hitting Shift-Command-C

The following article explains more about using Mac OS's Color Picker.

http://www.macworld.com/article/46746/2005/09/colorpickersecrets.html

SonarQube not picking up Unit Test Coverage

Based on https://github.com/SonarSource/sonar-examples/blob/master/projects/tycho/pom.xml, the following POM works for me:

<properties>
    <sonar.core.codeCoveragePlugin>jacoco</sonar.core.codeCoveragePlugin>
    <sonar.dynamicAnalysis>reuseReports</sonar.dynamicAnalysis>
    <sonar.jacoco.reportPath>${project.basedir}/../target/jacoco.exec</sonar.jacoco.reportPath>
</properties>
<build>
    <plugins>
        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.7.0.201403182114</version>
            <executions>
                <execution>
                    <goals>
                        <goal>prepare-agent</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <destFile>${sonar.jacoco.reportPath}</destFile>
            </configuration>
        </plugin>
    </plugins>
</build>
  • Setting the destination file to the report path ensures that Sonar reads exactly the file JaCoCo generates.
  • The report path should be outside the projects' directories to take cross-project coverage into account (e.g. in case of Tycho where the convention is to have separate projects for tests).
  • The reuseReports setting prevents the deletion of the JaCoCo report file before it is read! (Since 4.3, this is the default and is deprecated.)

Then I just run

mvn clean install
mvn sonar:sonar

How to inject JPA EntityManager using spring

The latest Spring + JPA versions solve this problem fundamentally. You can learn more how to use Spring and JPA togather in a separate thread

IllegalMonitorStateException on wait() call

Not sure if this will help somebody else out or not but this was the key part to fix my problem in user "Tom Hawtin - tacklin"'s answer above:

synchronized (lock) {
    makeWakeupNeeded();
    lock.notifyAll();
}

Just the fact that the "lock" is passed as an argument in synchronized() and it is also used in "lock".notifyAll();

Once I made it in those 2 places I got it working

Check if string ends with certain pattern

This is really simple, the String object has an endsWith method.

From your question it seems like you want either /, , or . as the delimiter set.

So:

String str = "This.is.a.great.place.to.work.";

if (str.endsWith(".work.") || str.endsWith("/work/") || str.endsWith(",work,"))
     // ... 

You can also do this with the matches method and a fairly simple regex:

if (str.matches(".*([.,/])work\\1$"))

Using the character class [.,/] specifying either a period, a slash, or a comma, and a backreference, \1 that matches whichever of the alternates were found, if any.

How to remove frame from matplotlib (pyplot.figure vs matplotlib.figure ) (frameon=False Problematic in matplotlib)

plt.axis('off')
plt.savefig(file_path, bbox_inches="tight", pad_inches = 0)

plt.savefig has those options in itself, just need to set axes off before

How to get Last record from Sqlite?

The previous answers assume that there is an incrementing integer ID column, so MAX(ID) gives the last row. But sometimes the keys are of text type, not ordered in a predictable way. So in order to take the last 1 or N rows (#Nrows#) we can follow a different approach:

Select * From [#TableName#]  LIMIT #Nrows# offset cast((SELECT count(*)  FROM [#TableName#]) AS INT)- #Nrows#

Python's "in" set operator

Yes, but it also means hash(b) == hash(x), so equality of the items isn't enough to make them the same.

How do I select the parent form based on which submit button is clicked?

To get the form that the submit is inside why not just

this.form

Easiest & quickest path to the result.

toBe(true) vs toBeTruthy() vs toBeTrue()

There are a lot many good answers out there, i just wanted to add a scenario where the usage of these expectations might be helpful. Using element.all(xxx), if i need to check if all elements are displayed at a single run, i can perform -

expect(element.all(xxx).isDisplayed()).toBeTruthy(); //Expectation passes
expect(element.all(xxx).isDisplayed()).toBe(true); //Expectation fails
expect(element.all(xxx).isDisplayed()).toBeTrue(); //Expectation fails

Reason being .all() returns an array of values and so all kinds of expectations(getText, isPresent, etc...) can be performed with toBeTruthy() when .all() comes into picture. Hope this helps.

TensorFlow, "'module' object has no attribute 'placeholder'"

Solution: Do not use "tensorflow" as your filename.

Notice that you use tensorflow.py as your filename. And I guess you write code like:

import tensorflow as tf

Then you are actually importing the script file "tensorflow.py" that is under your current working directory, rather than the "real" tensorflow module from Google.

Here is the order in which a module will be searched when importing:

  1. The directory containing the input script (or the current directory when no file is specified).

  2. PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH).

  3. The installation-dependent default.

ORA-01861: literal does not match format string

Remove the TO_DATE in the WHERE clause

TO_DATE (alarm_datetime,'DD.MM.YYYY HH24:MI:SS')

and change the code to

alarm_datetime

The error comes from to_date conversion of a date column.

Added Explanation: Oracle converts your alarm_datetime into a string using its nls depended date format. After this it calls to_date with your provided date mask. This throws the exception.

Ruby get object keys as array

An alternative way if you need something more (besides using the keys method):

hash = {"apple" => "fruit", "carrot" => "vegetable"}
array = hash.collect {|key,value| key }

obviously you would only do that if you want to manipulate the array while retrieving it..

redirect while passing arguments

I'm a little confused. "foo.html" is just the name of your template. There's no inherent relationship between the route name "foo" and the template name "foo.html".

To achieve the goal of not rewriting logic code for two different routes, I would just define a function and call that for both routes. I wouldn't use redirect because that actually redirects the client/browser which requires them to load two pages instead of one just to save you some coding time - which seems mean :-P

So maybe:

def super_cool_logic():
    # execute common code here

@app.route("/foo")
def do_foo():
    # do some logic here
    super_cool_logic()
    return render_template("foo.html")

@app.route("/baz")
def do_baz():
    if some_condition:
        return render_template("baz.html")
    else:
        super_cool_logic()
        return render_template("foo.html", messages={"main":"Condition failed on page baz"})

I feel like I'm missing something though and there's a better way to achieve what you're trying to do (I'm not really sure what you're trying to do)

Best way to find os name and version in Unix/Linux platform

With and Linux::Distribution, the cleanest solution for an old problem :

#!/bin/sh

perl -e '
    use Linux::Distribution qw(distribution_name distribution_version);

    my $linux = Linux::Distribution->new;
    if(my $distro = $linux->distribution_name()) {
          my $version = $linux->distribution_version();
          print "you are running $distro";
          print " version $version" if $version;
          print "\n";
    } else {
          print "distribution unknown\n";
    }
'

how to break the _.each function in underscore.js

You can have a look to _.some instead of _.each. _.some stops traversing the list once a predicate is true. Result(s) can be stored in an external variable.

_.some([1, 2, 3], function(v) {
    if (v == 2) return true;
})

See http://underscorejs.org/#some

Is it possible to have a HTML SELECT/OPTION value as NULL using PHP?

In php 7 you can do:

$_POST['value'] ?? null;

If value is equal to '' as said in other answers it will also send you null.

Failed to find 'ANDROID_HOME' environment variable

Execute: sudo gedit ~/.bashrc add

JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64
export JAVA_HOME
PATH=$PATH:$JAVA_HOME
export PATH
export ANDROID_HOME=~/Android/Sdk 
export PATH=${PATH}:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools

and

source ~/.bashrc

Arrays in type script

This is a very c# type of code:

var bks: Book[] = new Book[2];

In Javascript / Typescript you don't allocate memory up front like that, and that means something completely different. This is how you would do what you want to do:

var bks: Book[] = [];
bks.push(new Book());
bks[0].Author = "vamsee";
bks[0].BookId = 1;
return bks.length;

Now to explain what new Book[2]; would mean. This would actually mean that call the new operator on the value of Book[2]. e.g.:

Book[2] = function (){alert("hey");}
var foo = new Book[2]

and you should see hey. Try it

Handling the null value from a resultset in JAVA

The String being null is a very good chance, but when you see values in your table, yet a null is printed by the ResultSet, it might mean that the connection was closed before the value of ResultSet was used.

Class.forName("org.sqlite.JDBC");
con = DriverManager.getConnection("jdbc:sqlite:My_db.db");
String sql = ("select * from cust where cust_id='" + cus + "'");
pst = con.prepareStatement(sql);
rs = pst.executeQuery();
con.close();
System.out.println(rs.getString(1));

Would print null even if there are values.

Class.forName("org.sqlite.JDBC");
con = DriverManager.getConnection("jdbc:sqlite:My_db.db");
String sql = ("select * from cust where cust_id='" + cus + "'");
pst = con.prepareStatement(sql);
rs = pst.executeQuery();
System.out.println(rs.getString(1));
con.close();

Wouldn't print null if there are values in the table.

How to make certain text not selectable with CSS

The CSS below stops users from being able to select text.

-webkit-user-select: none; /* Safari */        
-moz-user-select: none; /* Firefox */
-ms-user-select: none; /* IE10+/Edge */
user-select: none; /* Standard */

To target IE9 downwards the html attribute unselectable must be used instead:

<p unselectable="on">Test Text</p>

MySQL "Or" Condition

Wrap your AND logic in parenthesis, like this:

mysql_query("SELECT * FROM Drinks WHERE email='$Email' AND (date='$Date_Today' OR date='$Date_Yesterday' OR date='$Date_TwoDaysAgo' OR date='$Date_ThreeDaysAgo' OR date='$Date_FourDaysAgo' OR date='$Date_FiveDaysAgo' OR date='$Date_SixDaysAgo' OR date='$Date_SevenDaysAgo')");

How to find all occurrences of an element in a list

How about:

In [1]: l=[1,2,3,4,3,2,5,6,7]

In [2]: [i for i,val in enumerate(l) if val==3]
Out[2]: [2, 4]

How to set multiple commands in one yaml file with Kubernetes?

If you want to avoid concatenating all commands into a single command with ; or && you can also get true multi-line scripts using a heredoc:

command: 
 - sh
 - "-c"
 - |
   /bin/bash <<'EOF'

   # Normal script content possible here
   echo "Hello world"
   ls -l
   exit 123

   EOF

This is handy for running existing bash scripts, but has the downside of requiring both an inner and an outer shell instance for setting up the heredoc.

Resizing SVG in html?

I have an SVG file in HTML [....] IS there any way to specify that you want an SVG image displayed smaller or larger than it actually is stored in the file system?

SVG graphics, like other creative works, are protected under copyright law in most countries. Depending on jurisdiction, license of the work or whether or not you are the copyright holder you may not be able to modify the SVG without violating copyright law, believe it or not.

But laws are tricky topics and sometimes you just want to get shit done. Therefore you may adjust the scale of the graphic without modifying the work itself using the img tag with width attribute within your HTML.

Using an external HTTP request to specify the size:

<img width="96" src="/path/to/image.svg">

Specifying size in markup using a Data URI:

<img width="96" src="data:image/svg+xml,...">

SVGs can be Optimized for Data URIs to create SVG Favicon images suitable for any size:

<link rel="icon" sizes="any" href="data:image/svg+xml,%3Csvg%20viewBox='0%200%2046%2045'%20xmlns='http://www.w3.org/2000/svg'%3E%3Ctitle%3EAfter%20Dark%3C/title%3E%3Cpath%20d='M.708%2045L23%20.416%2045.292%2045H.708zM35%2038L23%2019%2011%2038h24z'%20fill='%23000'/%3E%3C/svg%3E">

Exit while loop by user hitting ENTER key

a very simple solution would be, and I see you have said that you would like to see the simplest solution possible. A prompt for the user to continue after halting a loop Etc.

raw_input("Press<enter> to continue")

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

You can easily write the method to do that :

  public static String toCamelCase(final String init) {
    if (init == null)
        return null;

    final StringBuilder ret = new StringBuilder(init.length());

    for (final String word : init.split(" ")) {
        if (!word.isEmpty()) {
            ret.append(Character.toUpperCase(word.charAt(0)));
            ret.append(word.substring(1).toLowerCase());
        }
        if (!(ret.length() == init.length()))
            ret.append(" ");
    }

    return ret.toString();
}

Django CSRF Cookie Not Set

Method 1:

from django.shortcuts import render_to_response
return render_to_response(
    'history.html',
    RequestContext(request, {
        'account_form': form,
    })

Method 2 :

from django.shortcuts import render
return render(request, 'history.html', {
    'account_form': form,
})

Because render_to_response method may case some problem of response cookies.

What is the "N+1 selects problem" in ORM (Object-Relational Mapping)?

Let's say you have a collection of Car objects (database rows), and each Car has a collection of Wheel objects (also rows). In other words, Car ? Wheel is a 1-to-many relationship.

Now, let's say you need to iterate through all the cars, and for each one, print out a list of the wheels. The naive O/R implementation would do the following:

SELECT * FROM Cars;

And then for each Car:

SELECT * FROM Wheel WHERE CarId = ?

In other words, you have one select for the Cars, and then N additional selects, where N is the total number of cars.

Alternatively, one could get all wheels and perform the lookups in memory:

SELECT * FROM Wheel

This reduces the number of round-trips to the database from N+1 to 2. Most ORM tools give you several ways to prevent N+1 selects.

Reference: Java Persistence with Hibernate, chapter 13.

Instance member cannot be used on type

Another example is, you have class like :

@obc class Album: NSObject {
    let name:String
    let singer:Singer
    let artwork:URL
    let playingSong:Song


    // ...

    class func getCurrentlyPlayingSongLyric(duration: Int = 0) -> String {
        // ...
       return playingSong.lyric
    }
}

you will also get the same type of error like :

instance member x cannot be used on type x. 

It's because you assign your method with "class" keyword (which makes your method a type method) and using like :

Album.getCurrentlyPlayingSongLyric(duration: 5)

but who set the playingSong variable before? Ok. You shouldn't use class keyword for that case :

 // ...

 func getCurrentlyPlayingSongLyric(duration: Int = 0) -> String {
        // ...
       return playingSong.lyric
 }

 // ...

Now you're free to go.

How to plot data from multiple two column text files with legends in Matplotlib?

This is relatively simple if you use pylab (included with matplotlib) instead of matplotlib directly. Start off with a list of filenames and legend names, like [ ('name of file 1', 'label 1'), ('name of file 2', 'label 2'), ...]. Then you can use something like the following:

import pylab

datalist = [ ( pylab.loadtxt(filename), label ) for filename, label in list_of_files ]

for data, label in datalist:
    pylab.plot( data[:,0], data[:,1], label=label )

pylab.legend()
pylab.title("Title of Plot")
pylab.xlabel("X Axis Label")
pylab.ylabel("Y Axis Label")

You also might want to add something like fmt='o' to the plot command, in order to change from a line to points. By default, matplotlib with pylab plots onto the same figure without clearing it, so you can just run the plot command multiple times.

Where do alpha testers download Google Play Android apps?

It should be noted that releasing an alpha app for the first time may take up to a few hours before an opt-in link is available and invitations are sent out to the email addresses in your testers list.

From Google support:

After publishing an alpha/beta app for the first time, it may take a few hours for your test link to be available to testers. If you publish additional changes, they may take several hours to be available for testers. [source]

You may want to wait until you have an initial opt-in link before publishing more changes to the app because doing so is likely to increase your wait time for receiving your tester link; or, may lead to your testers testing with the incorrect version.

Hope that clears things up for anyone confused about why they don't have an opt-in link as depicted in screenshots in this SO thread!

How can I remove the last character of a string in python?

To remove the last character, just use a slice: my_file_path[:-1]. If you only want to remove a specific set of characters, use my_file_path.rstrip('/'). If you see the string as a file path, the operation is os.path.dirname. If the path is in fact a filename, I rather wonder where the extra slash came from in the first place.

Calling method using JavaScript prototype

if you define a function like this (using OOP)

function Person(){};
Person.prototype.say = function(message){
   console.log(message);
}

there is two ways to call a prototype function: 1) make an instance and call the object function:

var person = new Person();
person.say('hello!');

and the other way is... 2) is calling the function directly from the prototype:

Person.prototype.say('hello there!');

Why is it bad practice to call System.gc()?

It has already been explained that calling system.gc() may do nothing, and that any code that "needs" the garbage collector to run is broken.

However, the pragmatic reason that it is bad practice to call System.gc() is that it is inefficient. And in the worst case, it is horribly inefficient! Let me explain.

A typical GC algorithm identifies garbage by traversing all non-garbage objects in the heap, and inferring that any object not visited must be garbage. From this, we can model the total work of a garbage collection consists of one part that is proportional to the amount of live data, and another part that is proportional to the amount of garbage; i.e. work = (live * W1 + garbage * W2).

Now suppose that you do the following in a single-threaded application.

System.gc(); System.gc();

The first call will (we predict) do (live * W1 + garbage * W2) work, and get rid of the outstanding garbage.

The second call will do (live* W1 + 0 * W2) work and reclaim nothing. In other words we have done (live * W1) work and achieved absolutely nothing.

We can model the efficiency of the collector as the amount of work needed to collect a unit of garbage; i.e. efficiency = (live * W1 + garbage * W2) / garbage. So to make the GC as efficient as possible, we need to maximize the value of garbage when we run the GC; i.e. wait until the heap is full. (And also, make the heap as big as possible. But that is a separate topic.)

If the application does not interfere (by calling System.gc()), the GC will wait until the heap is full before running, resulting in efficient collection of garbage1. But if the application forces the GC to run, the chances are that the heap won't be full, and the result will be that garbage is collected inefficiently. And the more often the application forces GC, the more inefficient the GC becomes.

Note: the above explanation glosses over the fact that a typical modern GC partitions the heap into "spaces", the GC may dynamically expand the heap, the application's working set of non-garbage objects may vary and so on. Even so, the same basic principal applies across the board to all true garbage collectors2. It is inefficient to force the GC to run.


1 - This is how the "throughput" collector works. Concurrent collectors such as CMS and G1 use different criteria to decide when to start the garbage collector.

2 - I'm also excluding memory managers that use reference counting exclusively, but no current Java implementation uses that approach ... for good reason.

How to fix 'sudo: no tty present and no askpass program specified' error?

For Ubuntu 16.04 users

There is a file you have to read with:

cat /etc/sudoers.d/README

Placing a file with mode 0440 in /etc/sudoers.d/myuser with following content:

myuser  ALL=(ALL) NOPASSWD: ALL

Should fix the issue.

Do not forget to:

chmod 0440 /etc/sudoers.d/myuser

Select tableview row programmatically

There are two different methods for iPad and iPhone platforms, so you need to implement both:

  • selection handler and
  • segue.

    NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
    [self.tableView selectRowAtIndexPath:indexPath animated:NO scrollPosition:UITableViewScrollPositionNone];
    
    // Selection handler (for horizontal iPad)
    [self tableView:self.tableView didSelectRowAtIndexPath:indexPath];
    
    // Segue (for iPhone and vertical iPad)
    [self performSegueWithIdentifier:"showDetail" sender:self];
    

Force table column widths to always be fixed regardless of contents

This works for me

td::after { 
content: ''; 
display: block; 
width: 30px;
}

Colorizing text in the console with C++

You can write methods and call like this


HANDLE  hConsole;
hConsole = GetStdHandle(STD_OUTPUT_HANDLE);
int col=12;

// color your text in Windows console mode
// colors are 0=black 1=blue 2=green and so on to 15=white  
// colorattribute = foreground + background * 16
// to get red text on yellow use 4 + 14*16 = 228
// light red on yellow would be 12 + 14*16 = 236

FlushConsoleInputBuffer(hConsole);
SetConsoleTextAttribute(hConsole, col);

cout << "Color Text";

SetConsoleTextAttribute(hConsole, 15); //set back to black background and white text

Bootstrap: Open Another Modal in Modal

For someone who use bootstrap 4 https://jsfiddle.net/helloroy/tmm9juoh/

_x000D_
_x000D_
var modal_lv = 0;_x000D_
$('.modal').on('shown.bs.modal', function (e) {_x000D_
    $('.modal-backdrop:last').css('zIndex',1051+modal_lv);_x000D_
    $(e.currentTarget).css('zIndex',1052+modal_lv);_x000D_
    modal_lv++_x000D_
});_x000D_
_x000D_
$('.modal').on('hidden.bs.modal', function (e) {_x000D_
    modal_lv--_x000D_
});
_x000D_
<script src="https://code.jquery.com/jquery-3.1.1.slim.min.js"></script>_x000D_
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>_x000D_
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet"/>_x000D_
_x000D_
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#modal-a">_x000D_
  Launch demo modal a_x000D_
</button>_x000D_
_x000D_
<div class="modal fade" id="modal-a" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">_x000D_
  <div class="modal-dialog" role="document">_x000D_
    <div class="modal-content">_x000D_
      <div class="modal-header">_x000D_
        <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>_x000D_
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">_x000D_
          <span aria-hidden="true">&times;</span>_x000D_
        </button>_x000D_
      </div>_x000D_
      <div class="modal-body">_x000D_
        <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#modal-b">_x000D_
  Launch another demo modal b_x000D_
</button>_x000D_
<p class="my-3">_x000D_
Not good for fade In._x000D_
</p>_x000D_
<p class="my-3">_x000D_
who help to improve?_x000D_
</p>_x000D_
      </div>_x000D_
      <div class="modal-footer">_x000D_
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>_x000D_
        <button type="button" class="btn btn-primary">Save changes</button>_x000D_
      </div>_x000D_
    </div>_x000D_
  </div>_x000D_
</div>_x000D_
_x000D_
<div class="modal fade" id="modal-b" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">_x000D_
  <div class="modal-dialog" role="document">_x000D_
    <div class="modal-content">_x000D_
      <div class="modal-header">_x000D_
        <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>_x000D_
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">_x000D_
          <span aria-hidden="true">&times;</span>_x000D_
        </button>_x000D_
      </div>_x000D_
      <div class="modal-body">_x000D_
        <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#modal-c">_x000D_
  Launch another demo modal c_x000D_
</button>_x000D_
<p class="my-3">_x000D_
But good enough for static modal_x000D_
</p>_x000D_
      </div>_x000D_
      <div class="modal-footer">_x000D_
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>_x000D_
        <button type="button" class="btn btn-primary">Save changes</button>_x000D_
      </div>_x000D_
    </div>_x000D_
  </div>_x000D_
</div>_x000D_
_x000D_
_x000D_
<div class="modal" id="modal-c" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">_x000D_
  <div class="modal-dialog" role="document">_x000D_
    <div class="modal-content">_x000D_
      <div class="modal-header">_x000D_
        <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>_x000D_
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">_x000D_
          <span aria-hidden="true">&times;</span>_x000D_
        </button>_x000D_
      </div>_x000D_
      <div class="modal-body">_x000D_
<p class="my-3">That's all.</p>_x000D_
      </div>_x000D_
      <div class="modal-footer">_x000D_
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>_x000D_
        <button type="button" class="btn btn-primary">Save changes</button>_x000D_
      </div>_x000D_
    </div>_x000D_
  </div>_x000D_
</div>
_x000D_
_x000D_
_x000D_

How to create a new variable in a data.frame based on a condition?

One obvious and straightforward possibility is to use "if-else conditions". In that example

x <- c(1, 2, 4)
y <- c(1, 4, 5)
w <- ifelse(x <= 1, "good", ifelse((x >= 3) & (x <= 5), "bad", "fair"))
data.frame(x, y, w)

** For the additional question in the edit** Is that what you expect ?

> d1 <- c("e", "c", "a")
> d2 <- c("e", "a", "b")
> 
> w <- ifelse((d1 == "e") & (d2 == "e"), 1, 
+    ifelse((d1=="a") & (d2 == "b"), 2,
+    ifelse((d1 == "e"), 3, 99)))
>     
> data.frame(d1, d2, w)
  d1 d2  w
1  e  e  1
2  c  a 99
3  a  b  2

If you do not feel comfortable with the ifelse function, you can also work with the if and else statements for such applications.

Where does linux store my syslog?

On my Ubuntu machine, I can see the output at /var/log/syslog.

On a RHEL/CentOS machine, the output is found in /var/log/messages.

This is controlled by the rsyslog service, so if this is disabled for some reason you may need to start it with systemctl start rsyslog.

As noted by others, your syslog() output would be logged by the /var/log/syslog file.
You can see system, user, and other logs at /var/log.

For more details: here's an interesting link.

Array initializing in Scala

If you know Array's length but you don't know its content, you can use

val length = 5
val temp = Array.ofDim[String](length)

If you want to have two dimensions array but you don't know its content, you can use

val row = 5
val column = 3
val temp = Array.ofDim[String](row, column)

Of course, you can change String to other type.

If you already know its content, you can use

val temp = Array("a", "b")

Can I do Android Programming in C++, C?

You should use Android NDK to develop performance-critical portions of your apps in native code. See Android NDK.

Anyway i don't think it is the right way to develop an entire application.

Hidden TextArea

but is the css style tag the correct way to get cross browser compatibility?

 <textarea style="display:none;" ></textarea>

or what I learned long ago....

     <textarea hidden ></textarea>

or
the global hidden element method:

    <textarea hidden="hidden" ></textarea>       

Spring CrudRepository findByInventoryIds(List<Long> inventoryIdList) - equivalent to IN clause

Yes, that is supported.

Check the documentation provided here for the supported keywords inside method names.

You can just define the method in the repository interface without using the @Query annotation and writing your custom query. In your case it would be as followed:

List<Inventory> findByIdIn(List<Long> ids);

I assume that you have the Inventory entity and the InventoryRepository interface. The code in your case should look like this:

The Entity

@Entity
public class Inventory implements Serializable {

  private static final long serialVersionUID = 1L;

  private Long id;

  // other fields
  // getters/setters

}

The Repository

@Repository
@Transactional
public interface InventoryRepository extends PagingAndSortingRepository<Inventory, Long> {

  List<Inventory> findByIdIn(List<Long> ids);

}

calculate the mean for each column of a matrix in R

For diversity: Another way is to converts a vector function to one that works with data frames by using plyr::colwise()

set.seed(1)
m <- data.frame(matrix(sample(100, 20, replace = TRUE), ncol = 4))

plyr::colwise(mean)(m)


#   X1   X2   X3   X4
# 1 47 64.4 44.8 67.8

What is Android's file system?

Similar to Linux:

  • /boot

  • /system

  • /recovery

  • /data

  • /cache

  • /misc

How to get query params from url in Angular 2?

Query and Path (Angular 8)

If you have url like https://myapp.com/owner/123/show?height=23 then use

combineLatest( [this.route.paramMap, this.route.queryParamMap] )
  .subscribe( ([pathParams, queryParams]) => {
    let ownerId = pathParams.get('ownerId');    // =123
    let height  = queryParams.get('height');    // =height
    // ...
  })

UPDATE

In case when you use this.router.navigate([yourUrl]); and your query parameters are embedded in yourUrl string then angular encodes a URL and you get something like this https://myapp.com/owner/123/show%3Fheight%323 - and above solution will give wrong result (queryParams will be empty, and query params can be glued to last path param if it is on the path end). In this case change the way of navigation to this

this.router.navigateByUrl(yourUrl);

MySQL - select data from database between two dates

You can use MySQL DATE function like below

For instance, if you want results between 2017-09-05 till 2017-09-09

SELECT DATE(timestamp_field) as date FROM stocks_annc WHERE DATE(timestamp_field) >= '2017-09-05' AND DATE(timestamp_field) <= '2017-09-09'

Make sure to wrap the dates within single quotation ''

Hope this helps.

mysql extract year from date format

TRY:

SELECT EXTRACT(YEAR FROM (STR_TO_DATE(subdateshow, '%d/%m/%Y')));

Wpf control size to content?

I had a user control which sat on page in a free form way, not constrained by another container, and the contents within the user control would not auto size but expand to the full size of what the user control was handed.

To get the user control to simply size to its content, for height only, I placed it into a grid with on row set to auto size such as this:

<Grid Margin="0,60,10,200">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <controls1:HelpPanel x:Name="HelpInfoPanel"
                         Visibility="Visible"
                         Width="570"
                         HorizontalAlignment="Right"
                         ItemsSource="{Binding HelpItems}"
                         Background="#FF313131" />
</Grid>

Run php script as daemon process

You can

  1. Use nohup as Henrik suggested.
  2. Use screen and run your PHP program as a regular process inside that. This gives you more control than using nohup.
  3. Use a daemoniser like http://supervisord.org/ (it's written in Python but can daemonise any command line program and give you a remote control to manage it).
  4. Write your own daemonise wrapper like Emil suggested but it's overkill IMO.

I'd recommend the simplest method (screen in my opinion) and then if you want more features or functionality, move to more complex methods.

Why would we call cin.clear() and cin.ignore() after reading input?

The cin.clear() clears the error flag on cin (so that future I/O operations will work correctly), and then cin.ignore(10000, '\n') skips to the next newline (to ignore anything else on the same line as the non-number so that it does not cause another parse failure). It will only skip up to 10000 characters, so the code is assuming the user will not put in a very long, invalid line.

PHP post_max_size overrides upload_max_filesize

upload_max_filesize is the limit of any single file. post_max_size is the limit of the entire body of the request, which could include multiple files.

Given post_max_size = 20M and upload_max_filesize = 6M you could upload up to 3 files of 6M each. If instead post_max_size = 6M and upload_max_filesize = 20M then you could only upload one 6M file before hitting post_max_size. It doesn't help to have upload_max_size > post_max_size.

It's not obvious how to recognize going over post_max_size. $_POST and $_FILES will be empty, but $_SERVER['CONTENT_LENGTH'] will be > 0. If the client just didn't upload any post variables or files, then $_SERVER['CONTENT_LENGTH'] will be 0.

Difference between document.addEventListener and window.addEventListener?

The window binding refers to a built-in object provided by the browser. It represents the browser window that contains the document. Calling its addEventListener method registers the second argument (callback function) to be called whenever the event described by its first argument occurs.

<p>Some paragraph.</p>
<script>
  window.addEventListener("click", () => {
    console.log("Test");
  });
</script>

Following points should be noted before select window or document to addEventListners

  1. Most of the events are same for window or document but some events like resize, and other events related to loading, unloading, and opening/closing should all be set on the window.
  2. Since window has the document it is good practice to use document to handle (if it can handle) since event will hit document first.
  3. Internet Explorer doesn't respond to many events registered on the window,so you will need to use document for registering event.

What are the differences and similarities between ffmpeg, libav, and avconv?

Confusing messages

These messages are rather misleading and understandably a source of confusion. Older Ubuntu versions used Libav which is a fork of the FFmpeg project. FFmpeg returned in Ubuntu 15.04 "Vivid Vervet".

The fork was basically a non-amicable result of conflicting personalities and development styles within the FFmpeg community. It is worth noting that the maintainer for Debian/Ubuntu switched from FFmpeg to Libav on his own accord due to being involved with the Libav fork.

The real ffmpeg vs the fake one

For a while both Libav and FFmpeg separately developed their own version of ffmpeg.

Libav then renamed their bizarro ffmpeg to avconv to distance themselves from the FFmpeg project. During the transition period the "not developed anymore" message was displayed to tell users to start using avconv instead of their counterfeit version of ffmpeg. This confused users into thinking that FFmpeg (the project) is dead, which is not true. A bad choice of words, but I can't imagine Libav not expecting such a response by general users.

This message was removed upstream when the fake "ffmpeg" was finally removed from the Libav source, but, depending on your version, it can still show up in Ubuntu because the Libav source Ubuntu uses is from the ffmpeg-to-avconv transition period.

In June 2012, the message was re-worded for the package libav - 4:0.8.3-0ubuntu0.12.04.1. Unfortunately the new "deprecated" message has caused additional user confusion.

Starting with Ubuntu 15.04 "Vivid Vervet", FFmpeg's ffmpeg is back in the repositories again.

libav vs Libav

To further complicate matters, Libav chose a name that was historically used by FFmpeg to refer to its libraries (libavcodec, libavformat, etc). For example the libav-user mailing list, for questions and discussions about using the FFmpeg libraries, is unrelated to the Libav project.

How to tell the difference

If you are using avconv then you are using Libav. If you are using ffmpeg you could be using FFmpeg or Libav. Refer to the first line in the console output to tell the difference: the copyright notice will either mention FFmpeg or Libav.

Secondly, the version numbering schemes differ. Each of the FFmpeg or Libav libraries contains a version.h header which shows a version number. FFmpeg will end in three digits, such as 57.67.100, and Libav will end in one digit such as 57.67.0. You can also view the library version numbers by running ffmpeg or avconv and viewing the console output.

If you want to use the real ffmpeg

Ubuntu 15.04 "Vivid Vervet" or newer

The real ffmpeg is in the repository, so you can install it with:

apt-get install ffmpeg

For older Ubuntu versions

Your options are:

These methods are non-intrusive, reversible, and will not interfere with the system or any repository packages.

Another possible option is to upgrade to Ubuntu 15.04 "Vivid Vervet" or newer and just use ffmpeg from the repository.

Also see

For an interesting blog article on the situation, as well as a discussion about the main technical differences between the projects, see The FFmpeg/Libav situation.

How to get input field value using PHP

<form action="" method="post">
<input type="text" name="subject" id="subject" value="Car Loan">
<button type="submit" name="ok">OK</button>
</form>
<?php
if(isset($_POST['ok'])){
echo $_POST['subject'];
}
?>

Pretty-Print JSON in Java

You can use small json library

String jsonstring = ....;
JsonValue json = JsonParser.parse(jsonstring);
String jsonIndendedByTwoSpaces = json.toPrettyString("  ");

Online code beautifier and formatter

I've used Quick Highlighter a lot. Works great for a huge list of languages.

Get full path of the files in PowerShell

If relative paths are what you want you can just use the -Name flag.

Get-ChildItem "C:\windows\System32" -Recurse -Filter *.txt -Name

How to output an Excel *.xls file from classic ASP

It's AddHeader, not AppendHeader.

<%@ Language=VBScript %>
<%  Option Explicit

Response.ContentType = "application/vnd.ms-excel"
Response.AddHeader "Content-Disposition", "attachment; filename=excelTest.xls"
%>
<table>
    <tr>
        <td>Test</td>
    </tr>
</table>

Update: I've written a blog post about how to generate Excel files in ASP Classic. It contains a rather useful piece of code to generate both xls and csv files.

Automatic Preferred Max Layout Width is not available on iOS versions prior to 8.0

I had this issue and was able to fix it by adding constraints to determine the max with for a label.

When dropping a multiline label in there is not constraint set to enforce the width inside the parent view. This is where the new PreferredMaxWidth comes into play. On iOS 7 and earlier you have to define the max width yourself. I simply added a 10px constraint to the left and right hand side of the label.

You can also add a <= width constraint which also fixes the issue.

So this is not actually a bug, you simply have to define the max width yourself. The explicit option mention in other answer will also work as you are setting this width value however you will have to modify this value if you want the max width to change based on the parent width (as you have explicitly set the width).

My above solution ensures the width is always maintained no matter how big the parent view is.