Python programming cheat sheet. Useful reference for beginners. Covers syntax, terminology, and more. Last Word For Python Comment Syntax. In this lesson, we have learned how to create comment lines in python.You can sue python comment syntax in your codes to explain the code to yourself or to the other python programmer. These are very useful line for python coders. You can use both “#” sign and triple quotes for comments. The result of both of them will be the same.

Basics

Print a number	print(123)
Print a string	print('test')
Adding numbers	print(1+2)
Variable assignment	number = 123
Print a variable	print(number)
Function call	x = min(1, 2)
Comment	# a comment

Types

Integer	42
String	'a string'
List	[1, 2, 3]
Tuple	(1, 2, 3)
Boolean	True

Useful functions

Write to the screen	print('hi')
Calculate length	len('test')
Minimum of numbers	min(1, 2)
Maximum of numbers	max(1, 2)
Cast to integer	int('123')
Cast to string	str(123)
Cast to boolean	bool(1)
Range of numbers	range(5, 10)

Other syntax

Return a value	return 123
Indexing	'test'[0]
Slicing	'test'[1:3]
Continue to next loop iteration	continue
Exit the loop	break
List append	numbers = numbers + [4]
List append (with method call)	numbers.append(4)
List item extraction	value = numbers[0]
List item assignment	numbers[0] = 123

Terminology

syntax	the arrangement of letters and symbols in code
program	a series of instructions for the computer
print	write text to the screen
string	a sequence of letters surrounded by quotes
variable	a storage space for values
value	examples: a string, an integer, a boolean
assignment	using = to put a value into a variable
function	a machine you put values into and values come out
call (a function)	to run the code of the function
argument	the input to a function call
parameter	the input to a function definition
return value	the value that is sent out of a function
conditional	an instruction that's only run if a condition holds
loop	a way to repeatedly run instructions
list	a type of value that holds other values
tuple	like a list, but cannot be changed
indexing	extracting one element at a certain position
slicing	extracting some elements in a row
dictionary	a mapping from keys to values

Reminders

• Strings and lists are indexed starting at 0, not 1
• Print and return are not the same concept
• The return keyword is only valid inside functions
• Strings must be surrounded by quotes
• You cannot put spaces in variable or function names
• You cannot add strings and integers without casting
• Consistent indentation matters
• Use a colon when writing conditionals, function definitions, and loops
• Descriptive variable names help you understand your code better

Conditionals

Lists

Defining functions

Loops

Dictionaries

Comparisons

Equals
Not equals	!=
Less than	<
Less than or equal	<=
Greater than	>

Useful methods

String to lowercase	'xx'.lower()
String to uppercase	'xx'.upper()
Split string by spaces	'a b c'.split(' ')
Remove whitespace around string	' a string '.strip()
Combine strings into one string	' '.join(['a', 'b'])
String starts with	'xx'.startswith('x')
String ends with	'xx'.endswith('x')
List count	[1, 2].count(2)
List remove	[1, 2].remove(2)
Dictionary keys	{1: 2}.keys()
Dictionary values	{1: 2}.values()
Dictionary key/value pairs	{1: 2}.items()

Python Syntax Cheat Sheet

Other neat bonus stuff

Python Syntax Cheat Sheet Reddit

Zip lists	zip([1, 2], ['one', 'two'])
Set	my_set = {1, 2, 3}
Set intersection	{1, 2} & {2, 3}
Set union	{1, 2} | {2, 3}
Index of list element	[1, 2, 3].index(2)
Sort a list	numbers.sort()
Reverse a list	numbers.reverse()
Sum of list	sum([1, 2, 3])
Numbering of list elements	for i, item in enumerate(items):
Read a file line by line	for line in open('file.txt'):
Read file contents	contents = open('file.txt').read()
Random number between 1 and 10	import random; x = random.randint(1, 10)
List comprehensions	[x+1 for x in numbers]
Check if any condition holds	any([True, False])
Check if all conditions hold	all([True, False])

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Cheat sheets can be really helpful when you’re trying a set of exercises related to a specific topic, or working on a project. Because you can only fit so much information on a single sheet of paper, most cheat sheets are a simple listing of syntax rules. This set of cheat sheets aims to remind you of syntax rules, but also remind you of important concepts as well. You can click here and download all of the original cheat sheets in a single document.

Python Syntax Guide

An updated version of these sheets is also available through Leanpub and Gumroad. The updated version includes a sheet that focuses on Git basics, a printer-friendly b&w version of each sheet, and each sheet as a separate document. The updated versions are available at no cost on both platforms.

Individual Sheet Descriptions

• Beginner’s Python Cheat Sheet
  • Provides an overview of the basics of Python including variables, lists, dictionaries, functions, classes, and more.
• Beginner’s Python Cheat Sheet - Lists
  • Focuses on lists: how to build and modify a list, access elements from a list, and loop through the values in a list. Also covers numerical lists, list comprehensions, tuples, and more.
• Beginner’s Python Cheat Sheet - Dictionaries
  • Focuses on dictionaries: how to build and modify a dictionary, access the information in a dictionary, and loop through dictionaries in a variety of ways. Includes sections on nesting lists and dictionaries, using an OrderedDict and more.
• Beginner’s Python Cheat Sheet - If Statements and While Loops
  • Focuses on if statements and while loops: how to write conditional tests with strings and numerical data, how to write simple and complex if statements, and how to accept user input. Also covers a variety of approaches to using while loops.
• Beginner’s Python Cheat Sheet - Functions
  • Focuses on functions: how to define a function and how to pass information to a function. Covers positional and keyword arguments, return values, passing lists, using modules, and more.
• Beginner’s Python Cheat Sheet - Classes
  • Focuses on classes: how to define and use a class. Covers attributes and methods, inheritance and importing, and more.
• Beginner’s Python Cheat Sheet - Files and Exceptions
  • Focuses on working with files, and using exceptions to handle errors that might arise as your programs run. Covers reading and writing to files, try-except-else blocks, and storing data using the json module.
• Beginner’s Python Cheat Sheet - Testing Your Code
  • Focuses on unit tests and test cases. How to test a function, and how to test a class.
• Beginner’s Python Cheat Sheet - Pygame
  • Focuses on creating games with Pygame. Creating a game window, rect objects, images, responding to keyboard and mouse input, groups, detecting collisions between game elements, and rendering text.
• Beginner’s Python Cheat Sheet - matplotlib
  • Focuses on creating visualizations with matplotlib. Making line graphs and scatter plots, customizing plots, making multiple plots, and working with time-based data.
• Beginner’s Python Cheat Sheet - Pygal
  • Focuses on creating visualizations with Pygal. Making line graphs, scatter plots, and bar graphs, styling plots, making multiple plots, and working with global datasets.
• Beginner’s Python Cheat Sheet - Django
  • Focuses on creating web apps with Django. Installing Django and starting a project, working with models, building a home page, using templates, using data, and making user accounts.

Available from No Starch Press and Amazon.