Tutorial by Examples: pre

Querying data present in arrays

An integer will be interpreted as an index lookup. IceCream.objects.filter(metadata__buyer__known_for__0='creating stack overflow') See the note in the "Remarks" section about chaining queries.

Django • JSONField - a PostgreSQL specific field

Detect Whether Expression is Valid

It is possible to detect whether an operator or function can be called on a type. To test if a class has an overload of std::hash, one can do this: #include <functional> // for std::hash #include <type_traits> // for std::false_type and std::true_type #include <utility> // for s...

C++ • Metaprogramming

Receiving JSON from an HTTP Request

If the mimetype of the HTTP request is application/json, calling request.get_json() will return the parsed JSON data (otherwise it returns None) from flask import Flask, jsonify app = Flask(__name__) @app.route('/api/echo-json', methods=['GET', 'POST', 'DELETE', 'PUT']) ...

Flask • Working with JSON

Using expression in string literals

You can use curly braces to interpolate expressions into string literals: def f(x: String) = x + x val a = "A" s"${a}" // "A" s"${f(a)}" // "AA" Without the braces, scala would only interpolate the identifier after the $ (in this case f...

Scala Language • String Interpolation

Basic WordPress loop structure

Each time WordPress loads the page, it will run main loop. The loop is the way to iterate over all elements related to the page you are currently on. Main loop will work on a global WP_Query object. The query has a globalized method have_posts(), that allows us to loop through all results. Finally...

WordPress • The Loop (main WordPress loop)

Spreadsheet to dict of DataFrames

with pd.ExcelFile('path_to_file.xls) as xl: d = {sheet_name: xl.parse(sheet_name) for sheet_name in xl.sheet_names}

pandas • Pandas IO tools (reading and saving data sets)

Simple lambda expressions

// A simple adder function defined as a lambda expression. // Unlike with regular functions, parameter types often may be omitted because the // compiler can infer their types let adder = |a, b| a + b; // Lambdas can span across multiple lines, like normal functions. let multiplier = |a: i32, ...

Rust • Closures and lambda expressions

Sorting sequence containers using lambda expressions (C++11)

C++11 // Include sequence containers #include <vector> #include <deque> #include <list> #include <array> #include <forward_list> // Include sorting algorithm #include <algorithm> class Base { public: // Constructor that set variable to the va...

C++ • Sorting

Block with

and



            
            
If the formatting (white space, new lines, indentation) of the code matters, use the pre element in combination with the code element:
&lt;pre&gt;
    &lt;code&gt;
    x = 42
    if x == 42:
        print &quot;x is …          … 42&quot;
    &lt;/code&gt;
&lt;/pre&gt;

You still have to esc...            

            
            
                
                    
                        HTML
                        •
                        Marking up computer code





    

        

            
            
                
                    Importing resources without "Deprecated" error
                
            

            
            
Using the Android API 23 or higher, very often such situation can be seen:

This situation is caused by the structural change of the Android API regarding getting the resources.
Now the function:
public int getColor(@ColorRes int id, @Nullable Theme theme) throws NotFoundException    

should ...            

            
            
                
                    
                        Android
                        •
                        Lint Warnings
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Asynchronous prepare
                
            

            
            
The MediaPlayer$prepare() is a blocking call and will freeze the UI till execution completes. To solve this problem, MediaPlayer$prepareAsync() can be used.
mMediaPlayer = ... // Initialize it here
mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener(){
    @Override
    public ...            

            
            
                
                    
                        Android
                        •
                        MediaPlayer
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Prerequisites
                
            

            
            
To get started programming with CUDA, download and install the CUDA Toolkit and developer driver. The toolkit includes nvcc, the NVIDIA CUDA Compiler, and other software necessary to develop CUDA applications. The driver ensures that GPU programs run correctly on CUDA-capable hardware, which you'll ...            

            
            
                
                    
                        cuda
                        •
                        Getting started with cuda
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Prepending an element to a container
                
            

            
            
Solution 1:
 $('#parent').prepend($('#child')); 

Solution 2:
 $('#child').prependTo($('#parent'));

Both solutions are prepending the element #child (adding at the beginning) to the element #parent.
Before:
&lt;div id=&quot;parent&quot;&gt;
  &lt;span&gt;other content&lt;/span&gt;
&lt;/di...            

            
            
                
                    
                        jQuery
                        •
                        Prepend
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Attribute names with no prefix
                
            

            
            
Elements and attributes behave differently with respect to default namespaces. This is often the source of confusion.
An attribute whose name has no prefix lives in no namespace, also when a default namespace is in scope.
&lt;?xml version=&quot;1.0&quot;?&gt;
&lt;foo attr=&quot;value&quot; xmlns=...            

            
            
                
                    
                        xml
                        •
                        Namespaces
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Using Predefined Constants for Date Format
                
            

            
            
We can use Predefined Constants for Date format in date() instead of the conventional date format strings since PHP 5.1.0.

Predefined Date Format Constants Available
DATE_ATOM - Atom (2016-07-22T14:50:01+00:00)
DATE_COOKIE - HTTP Cookies (Friday, 22-Jul-16 14:50:01 UTC)
DATE_RSS - RSS (Fri, 22...            

            
            
                
                    
                        PHP
                        •
                        Working with Dates and Time
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Preconditions
                
            

            
            
Preconditions allows methods to provide minimum required values for input parameters
Example...
void DoWork(string input)
{
    Contract.Requires(!string.IsNullOrEmpty(input));

    //do work
}

Static Analysis Result...


            

            
            
                
                    
                        .NET Framework
                        •
                        Code Contracts
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Prelude
                
            

            
            
Prelude is another popular starter kit. It features good support for various programming languages out-of-the-box including, notably - clojure. On *nix systems it can be installed with the following command:
curl -L https://git.io/epre | sh


            

            
            
                
                    
                        emacs
                        •
                        Starter Kits
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Regular expression
                
            

            
            
Let's say we want to replace only numbers with 2 digits: regular expression will find them with (\d\d)
SELECT REGEXP_REPLACE ('2, 5, and 10 are numbers in this example', '(\d\d)', '#')
FROM dual;

Results in:
'2, 5, and # are numbers in this example'

If I want to swap parts of the text, I us...            

            
            
                
                    
                        Oracle Database
                        •
                        String Manipulation
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Splitting Strings using a Correlated Table Expression
                
            

            
            
Sample Data:
CREATE TABLE table_name ( id, list ) AS
SELECT 1, 'a,b,c,d' FROM DUAL UNION ALL -- Multiple items in the list
SELECT 2, 'e'       FROM DUAL UNION ALL -- Single item in the list
SELECT 3, NULL      FROM DUAL UNION ALL -- NULL list
SELECT 4, 'f,,g'    FROM DUAL;          -- NULL item...            

            
            
                
                    
                        Oracle Database
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                        Splitting Delimited Strings
                        
                    
                    
                
            
        
    




    

        

            
            
                
                    Error handling of specific HTTP response codes (such as 404 Not Found)
                
            

            
            
using System.Net;

...

string serverResponse;
try 
{
    // Call a method that performs an HTTP request (per the above examples).
    serverResponse = PerformHttpRequest();
}
catch (WebException ex)
{
    if (ex.Status == WebExceptionStatus.ProtocolError)
    {
        HttpWebResponse...            

            
            
                
                    
                        C# Language
                        •
                        Performing HTTP requests