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Python Cheatsheet

Python is a popular high-level programming language known for its simplicity, readability, and versatility. It is widely used for web development, data analysis, artificial intelligence, and more.

Versions

Version Initial Release End of Life Latest Patch Release Release Date
3.10 October 4, 2021 October 2026 3.10.2 February 18, 2022
3.9 October 5, 2020 October 2025 3.9.10 October 4, 2021
3.8 October 14, 2019 October 2024 3.8.12 July 19, 2021
3.7 June 27, 2018 June 2023 3.7.12 June 28, 2021
3.6 December 23, 2016 December 2021 3.6.15 December 23, 2020
3.5 September 13, 2015 September 2020 3.5.10 March 13, 2017
2.7 April 4, 2010 January 2020 2.7.18 April 20, 2020

Basic Syntax

Variables and Data Types

# Variable assignment
x = 10
y = "hello"

# Data types
string = "hello"
integer = 42
float_num = 3.14
boolean = True
list = [1, 2, 3]
tuple = (1, 2, 3)
dictionary = {"key": "value"}

Here is a table that summarizes the basic data types and their sizes in Python:

Data Type Description Size (bytes)
int Integer 4 or 8
float Floating-point number 8
bool Boolean 1
str String 1 per character
list List 4 + (4 or 8) per element
tuple Tuple 4 + (4 or 8) per element
dict Dictionary Varies

Control Flow

# If statement
if x > 5:
    print("x is greater than 5")
elif x == 5:
    print("x is equal to 5")
else:
    print("x is less than 5")

# For loop
for i in range(5):
    print(i)

# While loop
while x < 20:
    x += 1

# Break and continue
for i in range(10):
    if i == 5:
        continue
    if i == 8:
        break
    print(i)

Functions

# Define a function
def greet(name):
    print("Hello, " + name)

# Call a function
greet("Alice")

# Return a value from a function
def square(x):
    return x * x

result = square(5)
print(result)

Built-in Functions

Type Conversion

# Convert to integer
x = int("42")

# Convert to float
y = float("3.14")

# Convert to string
z = str(42)

String Manipulation

# Concatenate strings
greeting = "Hello"
name = "Alice"
message = greeting + ", " + name

# Replace a substring
text = "The quick brown fox"
new_text = text.replace("quick", "slow")

# Split a string into a list
sentence = "This is a sentence"
words = sentence.split(" ")

Lists and Tuples

# Access an element by index
my_list = [1, 2, 3]
first_element = my_list[0]

# Add an element to a list
my_list.append(4)

# Create a tuple
my_tuple = (1, 2, 3)

# Unpack a tuple
a, b, c = my_tuple

Dictionaries

# Create a dictionary
my_dict = {"name": "Alice", "age": 30}

# Access a value by key
name = my_dict["name"]

# Add a key-value pair to a dictionary
my_dict["location"] = "New York"

# Loop through a dictionary
for key, value in my_dict.items():
    print(key + ": " + str(value))

Classes

  • Blueprint for creating objects
  • Variables and methods inside a class
  • Use class keyword to define a class
  • Examples:
  class Student:
      def __init__(self, roll_no, name):
          self.roll_no = roll_no
          self.name = name
      def display_details(self):
          print("Roll No:", self.roll_no)
          print("Name:", self.name)

Additional Resources