Data structures, control flow, functions, OOP, I/O, and standard-library hints support daily Python and interview prep. The Python roadmap sequences exercises and milestones that reference the same keywords you look up here.

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Python Programming Cheatsheet

Quick reference guide for Python syntax and concepts from basic to advanced level.

Updated Python 3.10+ Comprehensive

Python Basics

Variables & Data Types

# Variable assignment
x = 5
name = "Alice"
is_active = True
pi = 3.14159

# Multiple assignment
a, b, c = 1, 2, 3

# Dynamic typing
x = 5 # integer
x = "five" # now a string

Basic Operators

# Arithmetic
sum = 5 + 3
diff = 10 - 2
product = 4 * 5
quotient = 15 / 3 # float division
floor_div = 15 // 3 # integer division
remainder = 15 % 4
power = 2 ** 3 # 8 (2 to the power of 3)

# Comparison
x == y # equal
x != y # not equal
x > y
x <= y

# Logical
x and y
x or y
not x

Control Flow

Conditionals

# If-elif-else
if x > 0:
  print("Positive")
elif x < 0:
  print("Negative")
else:
  print("Zero")

# Ternary operator
result = "Even" if x % 2 == 0 else "Odd"

# Truthy/Falsy values
if my_list: # False if empty
  print("List has items")

Loops

# For loop
for i in range(5):
  print(i) # 0 to 4

# While loop
count = 0
while count < 5:
  print(count)
  count += 1

# Loop control
for num in range(10):
  if num == 3:
    continue
  if num == 7:
    break
  print(num)

Data Structures

Lists

# List creation
numbers = [1, 2, 3, 4, 5]
mixed = [1, "two", 3.0, True]

# List operations
numbers.append(6) # [1,2,3,4,5,6]
numbers.insert(0, 0) # [0,1,2,3,4,5,6]
numbers.remove(3) # removes first 3
popped = numbers.pop() # removes and returns 6

# Slicing
first_two = numbers[:2]
last_three = numbers[-3:]
reversed_list = numbers[::-1]

# List comprehension
squares = [x**2 for x in numbers if x % 2 == 0]

Dictionaries

# Dictionary creation
person = {"name": "Alice", "age": 30}

# Accessing values
name = person["name"]
age = person.get("age", 0) # 0 is default

# Modifying
person["age"] = 31
person["city"] = "New York"

# Dictionary methods
keys = person.keys()
values = person.values()
items = person.items()

# Dictionary comprehension
squares = {x: x*x for x in range(5)}

# Merging dictionaries (Python 3.9+)
dict1 = {"a": 1}
dict2 = {"b": 2}
merged = dict1 | dict2

Tuples & Sets

# Tuples (immutable)
point = (10, 20)
x, y = point # unpacking

# Single element tuple
single = (42,) # comma is required

# Sets (unique elements)
primes = {2, 3, 5, 7}
primes.add(11)
primes.discard(2)

# Set operations
odds = {1, 3, 5, 7, 9}
evens = {2, 4, 6, 8}
union = odds | evens
intersection = odds & primes
difference = odds - primes

Strings

# String creation
s1 = 'Single quotes'
s2 = "Double quotes"
s3 = f"Hello {name}" # f-string (Python 3.6+)

# String methods
s = " Hello, World! "
s.strip() # "Hello, World!"
s.upper() # " HELLO, WORLD! "
s.replace("World", "Python")
words = s.split(",") # [' Hello', ' World! ']

# String formatting
name, age = "Alice", 30
msg = "{} is {} years old".format(name, age)
msg = f"{name} is {age} years old"

Functions

Function Basics

# Function definition
def greet(name):
  return f"Hello, {name}!"

# Function with default arguments
def power(base, exponent=2):
  return base ** exponent

# Function with variable arguments
def sum_all(*args):
  return sum(args)

# Function with keyword arguments
def person_info(**kwargs):
  for key, value in kwargs.items():
    print(f"{key}: {value}")

Lambda & Advanced Functions

# Lambda functions
square = lambda x: x * x
result = square(5) # 25

# Using lambda with map
numbers = [1, 2, 3, 4]
squared = list(map(lambda x: x**2, numbers))

# Using lambda with filter
evens = list(filter(lambda x: x % 2 == 0, numbers))

# Using lambda with sorted
points = [(1, 2), (3, 1), (5, 0)]
sorted_points = sorted(points, key=lambda x: x[1])

Advanced Topics

Classes & OOP

# Class definition
class Dog:
  # Class attribute
  species = "Canis familiaris"

  # Initializer
  def __init__(self, name, age):
    self.name = name # instance attribute
    self.age = age

  # Instance method
  def description(self):
    return f"{self.name} is {self.age} years old"

# Creating instances
buddy = Dog("Buddy", 9)
miles = Dog("Miles", 4)

# Inheritance
class Bulldog(Dog):
  def run(self, speed):
    return f"{self.name} runs at {speed} mph"

Error Handling

# Try-except block
try:
  result = 10 / 0
except ZeroDivisionError:
  print("Cannot divide by zero!")

# Multiple exceptions
try:
  value = int("not_a_number")
except (ValueError, TypeError):
  print("Value or type error occurred")

# Else and finally
try:
  file = open("file.txt")
except FileNotFoundError:
  print("File not found")
else:
  print(file.read())
  file.close()
finally:
  print("Execution complete")

# Raising exceptions
if x < 0:
  raise ValueError("x should be non-negative")
Quick reference guide

Comprehensive Python Cheatsheet & Examples Cheatsheet Reference

This Python Cheatsheet & Examples cheatsheet on Nikhil Learn Hub collects syntax, commands, and practical snippets for quick revision. Learn Python with syntax, commands, functions, examples, and best practices for beginners and programmers.

Use the reference cards and examples above during coding sessions; return here instead of scattered searches when you need dependable reminders. New learners can pair this sheet with the Python tutorial. Follow the Python learning roadmap when you want structured lessons beyond one-page lookups.

Quick lookup coverage

  • Syntax, built-ins, and data structures
  • File I/O, OOP, and standard-library hints
  • Common scripting and interview patterns

How to study with this sheet

  • Data science and automation cross-over
  • Pair with Python roadmap milestones
  • Contest and notebook speed tricks

Who Should Use This Cheatsheet

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