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