Tutorial by Examples: v

print_r() - Outputting Arrays and Objects for debugging print_r will output a human readable format of an array or object. You may have a variable that is an array or object. Trying to output it with an echo will throw the error: Notice: Array to string conversion. You can instead use the print_r...

A single case in a switch statement can match on multiple values. let number = 3 switch number { case 1, 2: print("One or Two!") case 3: print("Three!") case 4, 5, 6: print("Four, Five or Six!") default: print("Not One, Two, Three, Four, F...

It is often necessary to generate a new array based on the values of an existing array. For example, to generate an array of string lengths from an array of strings: 5.1 ['one', 'two', 'three', 'four'].map(function(value, index, arr) { return value.length; }); // → [3, 3, 5, 4] 6 ['one...

Python lists are zero-indexed, and act like arrays in other languages. lst = [1, 2, 3, 4] lst[0] # 1 lst[1] # 2 Attempting to access an index outside the bounds of the list will raise an IndexError. lst[4] # IndexError: list index out of range Negative indices are interpreted as countin...

dictionary = {"Hello": 1234, "World": 5678} print(dictionary["Hello"]) The above code will print 1234. The string "Hello" in this example is called a key. It is used to lookup a value in the dict by placing the key in square brackets. The number 1234 is ...

The filter() method creates an array filled with all array elements that pass a test provided as a function. 5.1 [1, 2, 3, 4, 5].filter(function(value, index, arr) { return value > 2; }); 6 [1, 2, 3, 4, 5].filter(value => value > 2); Results in a new array: [3, 4, 5] Fi...

To iterate through a list you can use for: for x in ['one', 'two', 'three', 'four']: print(x) This will print out the elements of the list: one two three four The range function generates numbers which are also often used in a for loop. for x in range(1, 6): print(x) The res...

Enum cases can contain one or more payloads (associated values): enum Action { case jump case kick case move(distance: Float) // The "move" case has an associated distance } The payload must be provided when instantiating the enum value: performAction(.jump) performA...

Enums without payloads can have raw values of any literal type: enum Rotation: Int { case up = 0 case left = 90 case upsideDown = 180 case right = 270 } Enums without any specific type do not expose the rawValue property enum Rotation { case up case right cas...

Logical OR (||), reading left to right, will evaluate to the first truthy value. If no truthy value is found, the last value is returned. var a = 'hello' || ''; // a = 'hello' var b = '' || []; // b = [] var c = '' || undefined; // c = undefined var d = 1 |...

Functions can return a value that you can use directly: def give_me_five(): return 5 print(give_me_five()) # Print the returned value # Out: 5 or save the value for later use: num = give_me_five() print(num) # Print the saved returned value # Out: 5 or use the value f...

Sometimes you don't want to have your function accessible/stored as a variable. You can create an Immediately Invoked Function Expression (IIFE for short). These are essentially self-executing anonymous functions. They have access to the surrounding scope, but the function itself and any internal va...

min(7,2,1,5) # Output: 1 max(7,2,1,5) # Output: 7

For every infix operator, e.g. + there is a operator-function (operator.add for +): 1 + 1 # Output: 2 from operator import add add(1, 1) # Output: 2 even though the main documentation states that for the arithmetic operators only numerical input is allowed it is possible: from operator impo...

The basic closure syntax is { [capture list] (parameters) throws-ness -> return type in body }. Many of these parts can be omitted, so there are several equivalent ways to write simple closures: let addOne = { [] (x: Int) -> Int in return x + 1 } let addOne = { [] (x: Int) -> Int in...

In Python, variables inside functions are considered local if and only if they appear in the left side of an assignment statement, or some other binding occurrence; otherwise such a binding is looked up in enclosing functions, up to the global scope. This is true even if the assignment statement is ...

A for loop iterates over a sequence, so altering this sequence inside the loop could lead to unexpected results (especially when adding or removing elements): alist = [0, 1, 2] for index, value in enumerate(alist): alist.pop(index) print(alist) # Out: [1] Note: list.pop() is being used t...

There are several special variable types that a class can use for more easily sharing data. Instance variables, preceded by @. They are useful if you want to use the same variable in different methods. class Person def initialize(name, age) my_age = age # local variable, will be destroyed ...

We have three methods: attr_reader: used to allow reading the variable outside the class. attr_writer: used to allow modifying the variable outside the class. attr_accessor: combines both methods. class Cat attr_reader :age # you can read the age but you can never change it attr_writer...

Ruby has three access levels. They are public, private and protected. Methods that follow the private or protected keywords are defined as such. Methods that come before these are implicitly public methods. Public Methods A public method should describe the behavior of the object being created. T...