The Ultimate Python Cheat Sheet

python

#1

Hello everybody, This is Webster. I am going to write the Ultimate Cheat Sheet for the entire Python Programming Language that you’ll ever need.
I am sure you all are familiar with Python programming. Just in case if you don’t know what Python is:

Python is a widely used high-level, general-purpose, interpreted, dynamic programming language. Its design philosophy emphasises code readability, and its syntax allows programmers to express concepts in fewer lines of code than possible in languages such as C++ or Java.

In the Cheat Sheet, I’ll try to cover every single thing that you’ll need most of the time. But, If I forget to add something, let me know in the comments.

The Complete Python Cheat Sheet:

The Ultimate Python Cheat Sheet by Webster

The Ultimate Python Cheat Sheet by The Tech Bible

import is used to make specialty functions available

These are called modules

import random
import sys
import os

Hello world is just one line of code

print() outputs data to the screen

print(“Hello World”)

‘’‘
This is a multi-line comment
’’’

A variable is a place to store values

Its name is like a label for that value

name = "Webster"
print(name)

A variable name can contain letters, numbers, or _

but can’t start with a number

There are 5 data types Numbers, Strings, List, Tuple, Dictionary

You can store any of them in the same variable

name = 15
print(name)

The arithmetic operators +, -, *, /, %, **, //

** Exponential calculation

// Floor Division

print(“5 + 2 =”, 5+2)
print(“5 - 2 =”, 5-2)
print(“5 * 2 =”, 5*2)
print(“5 / 2 =”, 5/2)
print(“5 % 2 =”, 5%2)
print(“5 ** 2 =”, 5**2)
print(“5 // 2 =”, 5//2)

Order of Operation states * and / is performed before + and -

print(“1 + 2 - 3 * 2 =”, 1 + 2 - 3 * 2)
print("(1 + 2 - 3) * 2 =", (1 + 2 - 3) * 2)

A string is a string of characters surrounded by " or ’

If you must use a " or ’ between the same quote escape it with \

quote = "“Always remember your unique,”

A multi-line quote

multi_line_quote = ‘’’ just
like everyone else" ‘’’

print(quote + multi_line_quote)

To embed a string in output use %s

print("%s %s %s" % (‘I like the quote’, quote, multi_line_quote))

To keep from printing newlines use end=""

print(“I don’t like “,end=””)
print(“newlines”)

You can print a string multiple times with *

print(’\n’ * 5)

LISTS -------------

A list allows you to create a list of values and manipulate them

Each value has an index with the first one starting at 0

grocery_list = [‘Juice’, ‘Tomatoes’, ‘Potatoes’, ‘Bananas’]
print(‘The first item is’, grocery_list[1])

You can change the value stored in a list box

grocery_list[0] = "Green Juice"
print(grocery_list)

You can get a subset of the list with [min:up to but not including max]

print(grocery_list[1:3])

You can put any data type in a a list including a list

other_events = [‘Wash Car’, ‘Pick up Kids’, ‘Cash Check’]
to_do_list = [other_events, grocery_list]

print(to_do_list)

Get the second item in the second list (Boxes inside of boxes)

print(to_do_list[1][1])

You add values using append

grocery_list.append(‘onions’)
print(to_do_list)

Insert item at given index

grocery_list.insert(1, “Pickle”)

Remove item from list

grocery_list.remove(“Pickle”)

Sorts items in list

grocery_list.sort()

Reverse sort items in list

grocery_list.reverse()

del deletes an item at specified index

del grocery_list[4]
print(to_do_list)

We can combine lists with a +

to_do_list = other_events + grocery_list
print(to_do_list)

Get length of list

print(len(to_do_list))

Get the max item in list

print(max(to_do_list))

Get the minimum item in list

print(min(to_do_list))

TUPLES -------------

Values in a tuple can’t change like lists

pi_tuple = (3, 1, 4, 1, 5, 9)

Convert tuple into a list

new_tuple = list(pi_tuple)

Convert a list into a tuple

new_list = tuple(grocery_list)

tuples also have len(tuple), min(tuple) and max(tuple)

DICTIONARY or MAP -------------

Made up of values with a unique key for each value

Similar to lists, but you can’t join dicts with a +

super_villains = {‘Fiddler’ : ‘Isaac Bowin’,
‘Captain Cold’ : ‘Leonard Snart’,
‘Weather Wizard’ : ‘Mark Mardon’,
‘Mirror Master’ : ‘Sam Scudder’,
‘Pied Piper’ : ‘Thomas Peterson’}

BTW, Leonard Snart is not a Super Villain, he is my hero

print(super_villains[‘Captain Cold’])

Delete an entry

del super_villains[‘Fiddler’]
print(super_villains)

Replace a value

super_villains[‘Pied Piper’] = ‘Hartley Rathaway’

Print the number of items in the dictionary

print(len(super_villains))

Get the value for the passed key

print(super_villains.get(“Pied Piper”))

Get a list of dictionary keys

print(super_villains.keys())

Get a list of dictionary values

print(super_villains.values())

CONDITIONALS -------------

The if, else and elif statements are used to perform different

actions based off of conditions

Comparison Operators : ==, !=, >, <, >=, <=

The if statement will execute code if a condition is met

White space is used to group blocks of code in Python

Use the same number of proceeding spaces for blocks of code

age = 30
if age > 16 :
print(‘You are old enough to drive’)

Use an if statement if you want to execute different code regardless

of whether the condition ws met or not

if age > 16 :
print(‘You are old enough to drive’)
else :
print(‘You are not old enough to drive’)

If you want to check for multiple conditions use elif

If the first matches it won’t check other conditions that follow

if age >= 21 :
print(‘You are old enough to drive a tractor trailer’)
elif age >= 16:
print(‘You are old enough to drive a car’)
else :
print(‘You are not old enough to drive’)

You can combine conditions with logical operators

Logical Operators : and, or, not

if ((age >= 1) and (age <= 18)):
print(“You get a birthday party”)
elif (age == 21) or (age >= 65):
print(“You get a birthday party”)
elif not(age == 30):
print(“You don’t get a birthday party”)
else:
print(“You get a birthday party yeah”)

FOR LOOPS -------------

Allows you to perform an action a set number of times

Range performs the action 10 times 0 - 9

for x in range(0, 10):
print(x , ’ ', end="")

print(’\n’)

You can use for loops to cycle through a list

grocery_list = [‘Juice’, ‘Tomatoes’, ‘Potatoes’, ‘Bananas’]

for y in grocery_list:
print(y)

You can also define a list of numbers to cycle through

for x in [2,4,6,8,10]:
print(x)

You can double up for loops to cycle through lists

num_list =[[1,2,3],[10,20,30],[100,200,300]];

for x in range(0,3):
for y in range(0,3):
print(num_list[x][y])

WHILE LOOPS -------------

While loops are used when you don’t know ahead of time how many

times you’ll have to loop

random_num = random.randrange(0,100)

while (random_num != 15):
print(random_num)
random_num = random.randrange(0,100)

An iterator for a while loop is defined before the loop

i = 0;
while (i <= 20):
if(i%2 == 0):
print(i)
elif(i == 9):
# Forces the loop to end all together
break
else:
# Shorthand for i = i + 1
i += 1
# Skips to the next iteration of the loop
continue

i += 1

FUNCTIONS -------------

Functions allow you to reuse and write readable code

Type def (define), function name and parameters it receives

return is used to return something to the caller of the function

def addNumbers(fNum, sNum):
sumNum = fNum + sNum
return sumNum

print(addNumbers(1, 4))

Can’t get the value of rNum because it was created in a function

It is said to be out of scope

print(sumNum)

If you define a variable outside of the function it works every place

newNum = 0;
def subNumbers(fNum, sNum):
newNum = fNum - sNum
return newNum

print(subNumbers(1, 4))

USER INPUT -------------

print(‘What is your name?’)

Stores everything typed up until ENTER

name = sys.stdin.readline()

print(‘Hello’, name)

STRINGS -------------

A string is a series of characters surrounded by ’ or "

long_string = “I’ll catch you if you fall - The Floor”

Retrieve the first 4 characters

print(long_string[0:4])

Get the last 5 characters

print(long_string[-5:])

Everything up to the last 5 characters

print(long_string[:-5])

Concatenate part of a string to another

print(long_string[:4] + " be there")

String formatting

print("%c is my %s letter and my number %d number is %.5f" % (‘X’, ‘favorite’, 1, .14))

Capitalizes the first letter

print(long_string.capitalize())

Returns the index of the start of the string

case sensitive

print(long_string.find(“Floor”))

Returns true if all characters are letters ’ isn’t a letter

print(long_string.isalpha())

Returns true if all characters are numbers

print(long_string.isalnum())

Returns the string length

print(len(long_string))

Replace the first word with the second (Add a number to replace more)

print(long_string.replace(“Floor”, “Ground”))

Remove white space from front and end

print(long_string.strip())

Split a string into a list based on the delimiter you provide

quote_list = long_string.split(" ")
print(quote_list)

FILE I/O -------------

Overwrite or create a file for writing

test_file = open(“test.txt”, “wb”)

Get the file mode used

print(test_file.mode)

Get the files name

print(test_file.name)

Write text to a file with a newline

test_file.write(bytes(“Write me to the file\n”, ‘UTF-8’))

Close the file

test_file.close()

Opens a file for reading and writing

test_file = open(“test.txt”, “r+”)

Read text from the file

text_in_file = test_file.read()

print(text_in_file)

Delete the file

os.remove(“test.txt”)

CLASSES AND OBJECTS -------------

The concept of OOP allows us to model real world things using code

Every object has attributes (color, height, weight) which are object variables

Every object has abilities (walk, talk, eat) which are object functions

class Animal:
# None signifies the lack of a value
# You can make a variable private by starting it with __
__name = None
__height = None
__weight = None
__sound = None

# The constructor is called to set up or initialize an object
# self allows an object to refer to itself inside of the class
def __init__(self, name, height, weight, sound):
    self.__name = name
    self.__height = height
    self.__weight = weight
    self.__sound = sound
def set_name(self, name):
    self.__name = name
def set_height(self, height):
    self.__height = height
def set_weight(self, height):
    self.__height = height
def set_sound(self, sound):
    self.__sound = sound
def get_name(self):
    return self.__name
def get_height(self):
    return str(self.__height)
def get_weight(self):
    return str(self.__weight)
def get_sound(self):
    return self.__sound
def get_type(self):
    print("Animal")
def toString(self):
    return "{} is {} cm tall and {} kilograms and says {}".format(self.__name, self.__height, self.__weight, self.__sound)

How to create a Animal object

cat = Animal(‘Whiskers’, 33, 10, ‘Meow’)

print(cat.toString())

You can’t access this value directly because it is private

#print(cat.__name)

INHERITANCE -------------

You can inherit all of the variables and methods from another class

class Dog(Animal):
__owner = None

def __init__(self, name, height, weight, sound, owner):
    self.__owner = owner
    self.__animal_type = None
    # How to call the super class constructor
    super(Dog, self).__init__(name, height, weight, sound)
def set_owner(self, owner):
    self.__owner = owner
def get_owner(self):
    return self.__owner
def get_type(self):
    print ("Dog")
# We can overwrite functions in the super class
def toString(self):
    return "{} is {} cm tall and {} kilograms and says {}. His owner is {}".format(self.get_name(), self.get_height(), self.get_weight(), self.get_sound(), self.__owner)
# You don't have to require attributes to be sent
# This allows for method overloading
def multiple_sounds(self, how_many=None):
    if how_many is None:
        print(self.get_sound)
    else:
        print(self.get_sound() * how_many)

spot = Dog(“Spot”, 53, 27, “Ruff”, “Webster”)

print(spot.toString())

Polymorphism allows use to refer to objects as their super class

and the correct functions are called automatically

class AnimalTesting:
def get_type(self, animal):
animal.get_type()

test_animals = AnimalTesting()

test_animals.get_type(cat)
test_animals.get_type(spot)

spot.multiple_sounds(4)

Post originally written at: https://www.techbible.org/2016/07/ultimate-python-cheat-sheet/
Download the file: https://github.com/webster007/python_scripts/blob/master/Complete_python_cheat_sheet.py


#2

Thanks for this mate! I actually have something like this just in case I’m not thinking too well, and I forget something. Really helps out.


#3

Glad to know that you found it helpful.


(system) #4

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