Basics

Python variables, types, functions, and scope rules.

Python uses snake_case for variables and functions, and PascalCase for classes. The language is dynamically typed but supports optional type hints.

Comments

# Single-line comment
"""
Multi-line
comment / docstring
"""

Python has no keyword to declare a variable — assignment creates it:

name = "Ada"          # str
age = 30              # int
price = 9.99          # float
active = True         # bool

name: str = "Ada"
age: int = 30
prices: list[float] = [9.99, 4.50]

def greet(name: str) -> str:
    return f"Hello, {name}"

# Default arguments
def connect(host: str = "localhost", port: int = 5432):
    ...

square = lambda x: x ** 2

count = 0              # global

def increment():
    global count
    count += 1

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