Tutorial by Examples: re

The increment and decrement operators exist in prefix and postfix form. int a = 1; int b = 1; int tmp = 0; tmp = ++a; /* increments a by one, and returns new value; a == 2, tmp == 2 */ tmp = a++; /* increments a by one, but returns old value; a == 3, tmp == 2 */ tmp = --b; ...

Closures (also known as blocks or lambdas) are pieces of code which can be stored and passed around within your program. let sayHi = { print("Hello") } // The type of sayHi is "() -> ()", aka "() -> Void" sayHi() // prints "Hello" Like other fun...

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 ...

class MyClass { func sayHi() { print("Hello") } deinit { print("Goodbye") } } When a closure captures a reference type (a class instance), it holds a strong reference by default: let closure: () -> Void do { let obj = MyClass() // Captures a strong re...

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...

You can define a new class using the class keyword. class MyClass end Once defined, you can create a new instance using the .new method somevar = MyClass.new # => #<MyClass:0x007fe2b8aa4a18>

The simplest way to iterate over a file line-by-line: with open('myfile.txt', 'r') as fp: for line in fp: print(line) readline() allows for more granular control over line-by-line iteration. The example below is equivalent to the one above: with open('myfile.txt', 'r') as fp: ...

In the event that geolocation fails, your callback function will receive a PositionError object. The object will include an attribute named code that will have a value of 1, 2, or 3. Each of these numbers signifies a different kind of error; the getErrorCode() function below takes the PositionError....

with open(input_file, 'r') as in_file, open(output_file, 'w') as out_file: for line in in_file: out_file.write(line) Using the shutil module: import shutil shutil.copyfile(src, dst)

var name = name + "=", cookie_array = document.cookie.split(';'), cookie_value; for(var i=0;i<cookie_array.length;i++) { var cookie=cookie_array[i]; while(cookie.charAt(0)==' ') cookie = cookie.substring(1,cookie.length); if(cookie.indexOf(name)==0) ...

var expiry = new Date(); expiry.setTime(expiry.getTime() - 3600); document.cookie = name + "=; expires=" + expiry.toGMTString() + "; path=/" This will remove the cookie with a given name.

import json d = { 'foo': 'bar', 'alice': 1, 'wonderland': [1, 2, 3] } json.dumps(d) The above snippet will return the following: '{"wonderland": [1, 2, 3], "foo": "bar", "alice": 1}'

import json s = '{"wonderland": [1, 2, 3], "foo": "bar", "alice": 1}' json.loads(s) The above snippet will return the following: {u'alice': 1, u'foo': u'bar', u'wonderland': [1, 2, 3]}

The following snippet opens a JSON encoded file (replace filename with the actual name of the file) and returns the object that is stored in the file. import json with open(filename, 'r') as f: d = json.load(f)

git diff This will show the unstaged changes on the current branch from the commit before it. It will only show changes relative to the index, meaning it shows what you could add to the next commit, but haven't. To add (stage) these changes, you can use git add. If a file is staged, but was modi...

git diff --staged This will show the changes between the previous commit and the currently staged files. NOTE: You can also use the following commands to accomplish the same thing: git diff --cached Which is just a synonym for --staged or git status -v Which will trigger the verbose sett...

Python's str type also has a method for replacing occurences of one sub-string with another sub-string in a given string. For more demanding cases, one can use re.sub. str.replace(old, new[, count]): str.replace takes two arguments old and new containing the old sub-string which is to be replace...

window.setInterval() returns an IntervalID, which can be used to stop that interval from continuing to run. To do this, store the return value of window.setInterval() in a variable and call clearInterval() with that variable as the only argument: function waitFunc(){ console.log("This wil...

window.setTimout() returns a TimeoutID, which can be used to stop that timeout from running. To do this, store the return value of window.setTimeout() in a variable and call clearTimeout() with that variable as the only argument: function waitFunc(){ console.log("This will not be logged a...

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...