Skip to content

python-cheat-sheet.md

Latest commit

 

History

History
66 lines (47 loc) · 2.7 KB

python-cheat-sheet.md

File metadata and controls

66 lines (47 loc) · 2.7 KB
Raw

Python: Overview

Python is a high-level programming language created by Guido van Rossum in 1991. Whitespace matters in Python, and Python uses a syntax that allows programmers to use fewer lines of code. Everything in Python is an object (variables, functions, code).

Bytes and Byte Arrays

Used for converting strings

Conditionals

Uses if, elif, and else statements

Constructor Method

Constructor method is defined with def __init__

Decorators

Decorators are special functions that return other functions and are used to modify the way that a function works - they're often used as accessor functions.

Dictionaries

A dictionary is a set of key value pairs. All keys in a dictionary must be unique.

A dictionary can be created two different ways:

  dictionary = { 'a':1, 'b':2, 'c':3, 'd':'phrase'}

  dictionary = dict(a = 1, b = 2, c 3)

Generators

A generator object is an object that can be used in the context of an iterator. It uses the yield keyword, which means the first time the function is called, it will execute all the code, then the next time it's called, it will pick up where the yield is.

Immutable and Mutable Objects

  • Mutable objects may change value, immutable objects may not.
  • Most fundamental types in Python are immutable (numbers, strings, tuples)
  • Mutable objects include lists, dictionaries, and other objects depending on how they're implemented

Lists

Lists are declared the following way:

  x = [2,3,4,5]

Loops

Only has two ways of doing loops - for loops and while loops

Operators

Outside of the usual operators, Python also uses:

  • // where the results is the quotient in which the digits after the decimal point are removed. If one of the operands is negative, the result is floored (rounded away from zero)
  • ** performs exponential calculation

Bitwise operators

  • x << y returns x with the bits shifted to the left by y places
  • x >> y returns x with the bits shifted to the right by y places
  • x & y does a "bitwise and" - each bit of the output is 1 if the corresponding bit of x AND of y is 1, otherwise it's 0
  • x|y does a "bitwise or" - each bit of the output is 0 if the corresponding bit of x AND y is 0, otherwise it's 1
  • ~x returns the complement of x - the number you get by switching each 1 for a 0 and each 0 for a 1
  • x ^ y does a "bitwise exclusive or" - each bit of the output is the same as the corresponding bit in x if that bit in y is 0, and it's the complement of the bit in x if that bit in y is 1

Tuples

Consist of a number of values separated by commas. They are used for ordered pairs and returning several values form a function.

Tuples are created with the comma operator:

  newTuple = 2,3,4,5