Complete Python Cheat Sheet

This is a quick Python cheat sheet with Examples. It contain two parts:

• Python basics
  • This is just a basic overview
• Advanced topics
  • many more features and concepts in Python

Python basics cheat sheet

Python data types

Basic Python data types

• int (integers) - whole numbers
  • e.g. 1, 2, 3
• float (floating-point numbers) - numbers with a decimal point
  • e.g. 3.14, 0.01
• str (strings) - sequences of Unicode characters
  • e.g. "hello", 'world'
• bool (booleans)
  • True or False

Python Collections

• list - an ordered collection of items
  • e.g. [1, 2, 3]
• tuple - an ordered, immutable collection of items
  • e.g. (1, 2, 3)
• dict (dictionaries) - an unordered collection of key-value pairs
  • e.g. {'name': 'John', 'age': 30}
• set - an unordered collection of unique items
  • e.g. {1, 2, 3}

Type casting

Python Control structures

• if-elif-else - used to make decisions
• for - used to iterate over a collection or a range of numbers
• while - used to repeat a block of code until a condition is met

if-elif-else example

x = 4
y = 7
if x > y:
  print("x > y")
elif x < y:
  print("x < y")
else:
  print("x = y")  

for loop

pets = ["cat", "dog", "mouse"]
for pet in pets:
  print(pet)

while example

i = 1
while i < 3:
  print(i)
  i += 1

Functions in Python

• def - used to define a function
• return - used to return a value from a function

def some_function():
  print("Hello from a function")
 
def another_function():
  return 1

some_function()
print(another_function())

Classes

• class - used to define a class
• self - used to refer to the current instance of a class

class Student:
  def __init__(self, name, age):
	self.name = name
	self.age = age

s1 = Student("Dan", 17)
s2 = Student("Sam", 15)

print(s1.name)
print(s1.age)

Modules

• import - used to import a module

import math
from math import pi
from math import pi as PI
from . import package

Other

• None - represents a null value
• lambda - used to create small anonymous functions
• with - used to wrap the execution of a block of code with methods defined by a context manager

lambda example

x = lambda a : a + 1
print(x(3))

x = lambda a, b : a + b
print(x(3, 4))

x = lambda a, b, c : a * b * c
print(x(1, 2, 3))

with example

with open('file_path', 'w') as f:
	f.write('Hello world')

Exception Handling

f = open("demofile.txt")
try:
  f.write("Some text")
except:
  print("Error on file write")
finally:
  print("Always executed")
  f.close()

Python advanced cheat sheet

Arithmetic Operators

Comparison Operators

Boolean Operators

More Python operations

List operations

Dictionary operations

String Operations

String manipulation

Most used string operations

String formatting

f-string

year = 2016
event = 'Referendum'
f'Results of the {year} {event}'

'Results of the 2016 Referendum'

.format()

txt = "This is {0}, I'm {1}".format("Dan",17)

'This is Dan, I'm 17'

numbers

"The price is ${0:,.2f}".format(100.3373)

'The price is $100.34'

dates

from datetime import datetime
now = datetime.now()
'{:%Y-%m-%d %H:%M:%S}'.format(now)

'2023-01-05 11:03:55'

Slicing

Indexes and Slices of a = [0, 1, 2, 3, 4, 5]. Python slicing of string and lists works as follows:

string[start:end:step]
list[start:end:step]

• start is included, end - excluded
• Positive number - from left to right
• Negative number - from right to left

Data Formatting

from datetime import datetime
 
time = datetime.now()
print("no formatting:", time)
 
print("formatting:", time.strftime("%X"))

Python sys.argv

python sample.py Hello Python

• sys.argv[0] == 'sample.py'
• sys.argv[1] == 'Hello'
• sys.argv[2] == 'Python'

Note: sys.argv[0] is always the filename/script executed

Python environment setup

import os
os.environ

OS variables

List methods

• append(item)
• count(item)
• extend(list)
• index(item)
• insert(position, item)
• pop(position)
• remove(item)
• reverse()
• sort()
• insert(position, item)

More examples and comparison tuples, dict and set here: Python: Compare List vs Tuple vs Dictionary vs Set