Python Cheat Sheet

Data Types

Command	Description
int("123")	Convert a string or number to an integer
float("123")	Convert a string or number to a float
str(123)	Convert a number or boolean to a string
bool("abc")	Convert a value to a boolean

Lists

Command	Description
list.append(item)	Append an item to the end of the list
list.insert(index, item)	Insert an item at a given position
list.remove(item)	Remove the first occurrence of a value
list.pop([index])	Remove and return the item at index (default last)
list.index(item)	Return zero-based index in the list of the first item whose value is equal to x
list.count(item)	Return the number of times x appears in the list
list.sort(key=None, reverse=False)	Sort the items in the list in ascending order
list.reverse()	Reverse the elements of the list in place
len(list)	Return the number of elements in the list

Strings

Command	Description
str.capitalize()	Capitalize the first character of the string
str.upper()	Convert all characters of the string to uppercase
str.lower()	Convert all characters of the string to lowercase
str.swapcase()	Swap case of each character
str.title()	Titlecase the string
str.find(sub[, start[, end]])	Return the lowest index in the string where substring is found
str.replace(old, new[, count])	Replace occurrences of a substring within the string
str.split([sep[, maxsplit]])	Return a list of the words in the string, using sep as the delimiter string
str.join(iterable)	Concatenate any number of strings
len(str)	Return the length (number of characters) of the string

Tuples

Command	Description
tuple.count(item)	Return the number of times x appears in the tuple
tuple.index(item)	Return zero-based index in the tuple of the first item whose value is equal to x
len(tuple)	Return the number of elements in the tuple

Dictionaries

Command	Description
dict.get(key[, default])	Return the value for key if key is in the dictionary, else default
dict.items()	Return a new object of the dictionary’s items in (key, value) format
dict.keys()	Return a new object of the dictionary’s keys
dict.values()	Return a new object of the dictionary’s values
dict.pop(key[, default])	Remove specified key and return the corresponding value
dict.clear()	Remove all items from the dictionary
len(dict)	Return the number of items in the dictionary

Sets

Command	Description
set.add(item)	Add an element to a set
set.remove(item)	Remove an element from a set; it must be a member
set.discard(item)	Remove an element from a set if it is a member
set.pop()	Remove and return an arbitrary set element
set.clear()	Remove all elements from the set
len(set)	Return the number of elements in the set

Control Flow

Command	Description
if condition:	Checks if a condition is true
else:	Execute if the condition in the if statement is false
elif condition:	Checks for additional conditions if the initial if condition is false
for item in iterable:	Iterate over an iterable object
while condition:	Execute a block of code as long as a condition is true
break	Terminate the loop prematurely
continue	Skip the rest of the code inside a loop for the current iteration
pass	A null operation; nothing happens when it executes

Functions

Command	Description
def function_name(parameters):	Define a function
return value	Return a value from a function
function_name(arguments)	Call a function with arguments
lambda parameters: expression	Create an anonymous function (lambda function)

Error Handling

Command	Description
try:	Enclose code that might raise an exception
except ExceptionType:	Handle a specific type of exception
else:	Execute if the code in the try block doesn't raise an exception
finally:	Execute regardless of whether an exception was raised in the try block

File Handling

Command	Description
open(filename, mode)	Open a file. Mode can be 'r' for read, 'w' for write, 'a' for append, 'b' for binary, '+' for read/write
file.read([size])	Read the whole file or up to size bytes
file.readline()	Read the next line of the file
file.readlines()	Return a list of lines from the file
file.write(string)	Write a string to the file
file.close()	Close the file

Classes/Objects

Command	Description
class ClassName:	Define a class
def init(self, parameters):	Define a constructor for a class
def method_name(self, parameters):	Define a method in a class
ClassName.method_name(instance, arguments)	Call a method on an instance of a class

Modules

Command	Description
import module	Import a module
from module import name	Import a specific name from a module
import module as name	Import a module and give it a different name
module.name	Access a name from a module

Please remember to replace list, dict, set, tuple, str, ClassName, function_name, module, name, filename, item, iterable, condition, parameters, arguments, value, ExceptionType with your actual values or variable names.

List Comprehensions

Command	Description
[expression for item in iterable]	Create a new list by applying an expression to each item in an iterable
[expression for item in iterable if condition]	Create a new list by applying an expression to each item in an iterable that meets a condition

Dictionary Comprehensions

Command	Description
{key_expression: value_expression for item in iterable}	Create a new dictionary by applying a key/value expression to each item in an iterable
{key_expression: value_expression for item in iterable if condition}	Create a new dictionary by applying a key/value expression to each item in an iterable that meets a condition

Built-in Functions

Command	Description
print(object)	Print an object to the console
input(prompt)	Get user input
range(start, stop[, step])	Generate a sequence of numbers
len(collection)	Get the number of items in a collection
type(object)	Get the type of an object
isinstance(object, type)	Check if an object is an instance of a specific type
abs(number)	Get the absolute value of a number
max(iterable)	Get the maximum value from an iterable
min(iterable)	Get the minimum value from an iterable
sum(iterable)	Get the sum of all items in an iterable
sorted(iterable)	Get a new sorted list from an iterable

Math Functions (math module)

Command	Description
math.sqrt(number)	Return the square root of a number
math.pow(base, exp)	Return base raised to the power of exp
math.floor(number)	Return the largest integer less than or equal to a number
math.ceil(number)	Return the smallest integer greater than or equal to a number
math.pi	Return the constant pi
math.e	Return the constant e

Please remember to replace expression, item, iterable, condition, key_expression, value_expression, object, prompt, start, stop, step, collection, type, number, base, exp with your actual values or variable names.

Generators

Command	Description
(expression for item in iterable)	Create a new generator by applying an expression to each item in an iterable
yield expression	Suspend function’s execution and sends a value back to the caller, but retains enough state to enable function to resume where it left off
next(generator)	Retrieve the next item from a generator

Regular Expressions (re module)

Command	Description
re.match(pattern, string)	Determine if the regular expression matches at the beginning of the string
re.search(pattern, string)	Search the string for a match to the regular expression
re.findall(pattern, string)	Return all non-overlapping matches of the regular expression as a list of strings
re.sub(pattern, replace, string)	Replace the matches of the regular expression with a different string

Date and Time (datetime module)

Command	Description
datetime.datetime.now()	Get the current date and time
datetime.datetime(year, month, day[, hour[, minute[, second[, microsecond]]]])	Create a new datetime object
datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)	Create a new timedelta object
datetime_object.date()	Get the date portion of a datetime object
datetime_object.time()	Get the time portion of a datetime object
datetime_object.year	Get the year portion of a datetime object
datetime_object.month	Get the month portion of a datetime object
datetime_object.day	Get the day portion of a datetime object
datetime_object.hour	Get the hour portion of a datetime object
datetime_object.minute	Get the minute portion of a datetime object
datetime_object.second	Get the second portion of a datetime object
datetime_object.microsecond	Get the microsecond portion of a datetime object

Please remember to replace expression, item, iterable, pattern, string, replace, generator, year, month, day, hour, minute, second, microsecond, days, seconds, microseconds, milliseconds, minutes, hours, weeks, datetime_object with your actual values or variable names.