Functions & basics
Reusable building blocks — parameters, returns, scope, and clear function design.
How to Build a Subcommand Parser Tree with argparse in Python
Create a CLI with nested subcommands (like git) using argparse subparsers, where each subcommand maps to its own handler function.
import argparse
def cmd_add(args):
print(f"Adding {args.num1} + {args.num2} = {args.num1 + args.num2}")
def cmd_sub(args):
print(f"Subtracting {args.num1} - {args.num2} = {args.num1 - args.num2}")
def main():
parser = argparse.ArgumentParser(prog="calculator")
subparsers = parser.add_subparsers(d…How to Implement a Trampoline for Tail Recursion in Python
This code implements a trampoline decorator that converts tail-recursive functions into iterative loops, allowing deep recursion without hitting Python's recursion limit.
def trampoline(fn):
"""Convert a tail-recursive function into an iterative loop."""
def wrapper(*args, **kwargs):
result = fn(*args, **kwargs)
while callable(result):
result = result()
return result
return wrapper
@trampoline
def factorial(n, acc=1):
"""Tail-recursi…Browse by section
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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.