Functions & basics
Reusable building blocks — parameters, returns, scope, and clear function design.
How to Write a Context Manager Class in Python
Define a class with __enter__ and __exit__ to manage file resources safely using the with statement.
class FileReader:
def __init__(self, filename, mode="r"):
self.filename = filename
self.mode = mode
self.file = None
def __enter__(self):
self.file = open(self.filename, self.mode)
return self.file
def __exit__(self, exc_type, exc_val, exc_tb):
if self.file…Write a Pure Function Without Side Effects in Python
Defines a pure function that adds one to a number without modifying external state.
def add_one(x: int) -> int:
"""Adds 1 to the input without modifying any external state."""
return x + 1
if __name__ == "__main__":
original = 5
result = add_one(original)
print(f"Original: {original}")
print(f"Result: {result}")
print(f"Original unchanged: {original}")Browse by section
Each section groups closely related Python snippets.
Functions & basics — Python code examples
What you will find here
This page collects functions & basics snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
Samples vs tutorials and challenges
Samples are quick reference — one concept per page. For step-by-step teaching, use our Python tutorials. To test yourself, try quizzes or coding challenges. Clean up style with the Python formatter.