Tutorial by Examples: d

Variables are annotated using comments: x = 3 # type: int x = negate(x) x = 'a type-checker might catch this error' Python 3.x3.6 Starting from Python 3.6, there is also new syntax for variable annotations. The code above might use the form x: int = 3 Unlike with comments, it is also pos...

Double quoteSingle quoteAllows variable expansionPrevents variable expansionAllows history expansion if enabledPrevents history expansionAllows command substitutionPrevents command substitution* and @ can have special meaning* and @ are always literalsCan contain both single quote or double quoteSin...

x = 5 x += 7 for x in iterable: pass Each of the above statements is a binding occurrence - x become bound to the object denoted by 5. If this statement appears inside a function, then x will be function-local by default. See the "Syntax" section for a list of binding statements. ...

You can force deallocate objects even if their refcount isn't 0 in both Python 2 and 3. Both versions use the ctypes module to do so. WARNING: doing this will leave your Python environment unstable and prone to crashing without a traceback! Using this method could also introduce security problems ...

Create User Model rails generate model User email:string password_digest:string Add has_secure_password module to User model class User < ActiveRecord::Base has_secure_password end Now you can create a new user with password user = User.new email: '[email protected]', password: 'Password1', ...

To play audio using the Web Audio API, we need to get an ArrayBuffer of audio data and pass it to a BufferSource for playback. To get an audio buffer of the sound to play, you need to use the AudioContext.decodeAudioData method like so: const audioCtx = new (window.AudioContext || window.webkitAud...

When using prompt a user can always click Cancel and no value will be returned. To prevent empty values and make it more persistent: <h2>Welcome <span id="name"></span>!</h2> <script> // Persistent Prompt modal var userName; while(!userName) { userN...

A way to use confirm() is when some UI action does some destructive changes to the page and is better accompanied by a notification and a user confirmation - like i.e. before deleting a post message: <div id="post-102"> <p>I like Confirm modals.</p> <a data-dele...

Using the dataset property The new dataset property allows access (for both reading and writing) to all data attributes data-* on any element. <p>Countries:</p> <ul> <li id="C1" onclick="showDetails(this)" data-id="US" data-dial-code="1&q...

The code below will prompt for numbers and continue to add them to the beginning of a linked list. /* This program will demonstrate inserting a node at the beginning of a linked list */ #include <stdio.h> #include <stdlib.h> struct Node { int data; struct Node* next; }; ...

This way may seem to be uselss becuase you are using anonymous function to acomplish something that you can do it with join(); But if you need to make something to the strings while you are converting the Array to String, this can be useful. var arr = ['a', 'á', 'b', 'c'] function upper_lower (...

This example shows how to use two audio sources, and alter one of them based on the other. In this case we create an audio Ducker, that will lower the volume of the primary track if the secondary track produces sound. The ScriptProcessorNode will send regular events to its audioprocess handler. In ...

The dot function can also be used to compute vector dot products between two one-dimensional numpy arrays. >>> v = np.array([1,2]) >>> w = np.array([1,2]) >>> v.dot(w) 5 >>> np.dot(w,v) 5 >>> np.dot(v,w) 5

class Plane { enum Emergency: ErrorType { case NoFuel case EngineFailure(reason: String) case DamagedWing } var fuelInKilograms: Int //... init and other methods not shown func fly() throws { // ... if fuelInKilograms ...

const int a = 0; /* This variable is "unmodifiable", the compiler should throw an error when this variable is changed */ int b = 0; /* This variable is modifiable */ b += 10; /* Changes the value of 'b' */ a += 10; /* Throws a compiler error */ The const qualif...

process.argv is an array containing the command line arguments. The first element will be node, the second element will be the name of the JavaScript file. The next elements will be any additional command line arguments. Code Example: Output sum of all command line arguments index.js var sum = 0...

A singleton is a pattern that restricts the instantiation of a class to one instance/object. Using a decorator, we can define a class as a singleton by forcing the class to either return an existing instance of the class or create a new instance (if it doesn't exist). def singleton(cls): i...

Using vanilla mathematics: var from:Point = new Point(300, 10); var to:Point = new Point(75, 40); var a:Number = to.x - from.x; var b:Number = to.y - from.y; var distance:Number = Math.sqrt(a * a + b * b); Using inbuilt functionality of Point: var distance:Number = to.subtract(from).len...

var degrees:Number = radians * 180 / Math.PI;

var radians:Number = degrees / 180 * Math.PI;