Tutorial by Examples: io

In order to access the value of an Optional, it needs to be unwrapped. You can conditionally unwrap an Optional using optional binding and force unwrap an Optional using the ! operator. Conditionally unwrapping effectively asks "Does this variable have a value?" while force unwrapping sa...

Relational operators check if a specific relation between two operands is true. The result is evaluated to 1 (which means true) or 0 (which means false). This result is often used to affect control flow (via if, while, for), but can also be stored in variables. Equals "==" Checks whether...

Getting the minimum or maximum or using sorted depends on iterations over the object. In the case of dict, the iteration is only over the keys: adict = {'a': 3, 'b': 5, 'c': 1} min(adict) # Output: 'a' max(adict) # Output: 'c' sorted(adict) # Output: ['a', 'b', 'c'] To keep the dictionary ...

What can be documented? Examples of functions for various languages. A brief introduction of each tag. What is the difference between a question and a topic? Topics have a broader scope than questions; documentation topics that are asked as a question can be closed because they are too bro...

Arguments are defined in parentheses after the function name: def divide(dividend, divisor): # The names of the function and its arguments # The arguments are available by name in the body of the function print(dividend / divisor) The function name and its list of arguments are called...

Optional arguments can be defined by assigning (using =) a default value to the argument-name: def make(action='nothing'): return action Calling this function is possible in 3 different ways: make("fun") # Out: fun make(action="sleep") # Out: sleep # The argumen...

One can give a function as many arguments as one wants, the only fixed rules are that each argument name must be unique and that optional arguments must be after the not-optional ones: def func(value1, value2, optionalvalue=10): return '{0} {1} {2}'.format(value1, value2, optionalvalue1) Wh...

Arbitrary number of positional arguments: Defining a function capable of taking an arbitrary number of arguments can be done by prefixing one of the arguments with a * def func(*args): # args will be a tuple containing all values that are passed in for i in args: print(i) fun...

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...

Functions may accept closures (or other functions) as parameters: func foo(value: Double, block: () -> Void) { ... } func foo(value: Double, block: Int -> Int) { ... } func foo(value: Double, block: (Int, Int) -> String) { ... } Trailing closure syntax If a function's last parameter ...

There is a problem when using optional arguments with a mutable default type (described in Defining a function with optional arguments), which can potentially lead to unexpected behaviour. Explanation This problem arises because a function's default arguments are initialised once, at the point whe...

Python 3.x3.0 In Python 3, print functionality is in the form of a function: print("This string will be displayed in the output") # This string will be displayed in the output print("You can print \n escape characters too.") # You can print escape characters too. Pyth...

def input_number(msg, err_msg=None): while True: try: return float(raw_input(msg)) except ValueError: if err_msg is not None: print(err_msg) def input_number(msg, err_msg=None): while True: try: return ...

Overview Checkboxes and radio buttons are written with the HTML tag <input>, and their behavior is defined in the HTML specification. The simplest checkbox or radio button is an <input> element with a type attribute of checkbox or radio, respectively: <input type="checkbox&quo...

Python's string type provides many functions that act on the capitalization of a string. These include : str.casefold str.upper str.lower str.capitalize str.title str.swapcase With unicode strings (the default in Python 3), these operations are not 1:1 mappings or reversible. Most of thes...

A generator function is created with a function* declaration. When it is called, its body is not immediately executed. Instead, it returns a generator object, which can be used to "step through" the function's execution. A yield expression inside the function body defines a point at which...

A generator is iterable. It can be looped over with a for...of statement, and used in other constructs which depend on the iteration protocol. function* range(n) { for (let i = 0; i < n; ++i) { yield i; } } // looping for (let n of range(10)) { // n takes on the valu...

Since PHP 5.0, PDO has been available as a database access layer. It is database agnostic, and so the following connection example code should work for any of its supported databases simply by changing the DSN. // First, create the database handle //Using MySQL (connection via local socket): $d...

The basic syntax of SELECT with WHERE clause is: SELECT column1, column2, columnN FROM table_name WHERE [condition] The [condition] can be any SQL expression, specified using comparison or logical operators like >, <, =, <>, >=, <=, LIKE, NOT, IN, BETWEEN etc. The following ...

Definition: In computing, an event is an action or occurrence recognized by software that may be handled by the software. Computer events can be generated or triggered by the system, by the user or in other ways. Definition Source HTML events are "things" that happen to HTML ele...