Tutorial by Examples: io

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 ...

When both operands are numeric, they are compared normally: 1 < 2 // true 2 <= 2 // true 3 >= 5 // false true < false // false (implicitly converted to numbers, 1 > 0) When both operands are strings, they are compared lexicographically (according to alphabeti...

Program options can be handled with the getopt() function. It operates with a similar syntax to the POSIX getopt command, with additional support for GNU-style long options. #!/usr/bin/php // a single colon indicates the option takes a value // a double colon indicates the value may be omitted ...

The JSONSerialization class is built into Apple's Foundation framework. 2.2 Read JSON The JSONObjectWithData function takes NSData, and returns AnyObject. You can use as? to convert the result to your expected type. do { guard let jsonData = "[\"Hello\", \"JSON\"]&q...

An enum provides a set of related values: enum Direction { case up case down case left case right } enum Direction { case up, down, left, right } Enum values can be used by their fully-qualified name, but you can omit the type name when it can be inferred: let dir = Dire...

This example assumes Ruby and Ruby on Rails have already been installed properly. If not, you can find how to do it here. Open up a command line or terminal. To generate a new rails application, use rails new command followed by the name of your application: $ rails new my_app If you want to c...

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 |...

Using the def statement is the most common way to define a function in python. This statement is a so called single clause compound statement with the following syntax: def function_name(parameters): statement(s) function_name is known as the identifier of the function. Since a function def...

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...

Decorators augment the behavior of other functions or methods. Any function that takes a function as a parameter and returns an augmented function can be used as a decorator. # This simplest decorator does nothing to the function being decorated. Such # minimal decorators can occasionally be used ...

Decorators normally strip function metadata as they aren't the same. This can cause problems when using meta-programming to dynamically access function metadata. Metadata also includes function's docstrings and its name. functools.wraps makes the decorated function look like the original function b...

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...

When you define a function, it creates a scope. Everything defined within the function is not accessible by code outside the function. Only code within this scope can see the entities defined inside the scope. function foo() { var a = 'hello'; console.log(a); // => 'hello' } consol...

A Promise object represents an operation which has produced or will eventually produce a value. Promises provide a robust way to wrap the (possibly pending) result of asynchronous work, mitigating the problem of deeply nested callbacks (known as "callback hell"). States and control flow ...

The setTimeout() method calls a function or evaluates an expression after a specified number of milliseconds. It is also a trivial way to achieve an asynchronous operation. In this example calling the wait function resolves the promise after the time specified as first argument: function wait(ms) ...

A traditional for-loop A traditional for loop has three components: The initialization: executed before the look block is executed the first time The condition: checks a condition every time before the loop block is executed, and quits the loop if false The afterthought: performed every time a...

Optionals are a generic enum type that acts as a wrapper. This wrapper allows a variable to have one of two states: the value of the user-defined type or nil, which represents the absence of a value. This ability is particularly important in Swift because one of the stated design objectives of the ...

#include <stdio.h> /* increment: take number, increment it by one, and return it */ int increment(int i) { printf("increment %d by 1\n", i); return i + 1; } /* decrement: take number, decrement it by one, and return it */ int decrement(int i) { printf("...

#include <stdio.h> enum Op { ADD = '+', SUB = '-', }; /* add: add a and b, return result */ int add(int a, int b) { return a + b; } /* sub: subtract b from a, return result */ int sub(int a, int b) { return a - b; } /* getmath: return the appropriate m...

If you ignore files by using a pattern but have exceptions, prefix an exclamation mark(!) to the exception. For example: *.txt !important.txt The above example instructs Git to ignore all files with the .txt extension except for files named important.txt. If the file is in an ignored folder, y...