Python Recursion Guide

A hands-on Jupyter notebook that teaches recursive programming in Python through clear explanations, side‑by‑side iterative comparisons, simple performance checks, and practice exercises.

What’s inside

• practical_recursion.ipynb — a guided notebook covering fundamentals, patterns, performance, and 10 practical case studies.

Case studies covered

Case	Topic	Difficulty	Key Concept
1	Factorial	Easy	Linear recursion basics
2	Fibonacci	Medium	Binary recursion, exponential growth
3	Sum of List	Easy	Processing sequential data
4	Power Function	Easy	Mathematical recursion
5	Reverse String	Easy	String manipulation
6	Countdown	Easy	Visual recursion flow
7	Palindrome Checker	Medium	Two‑pointer recursion
8	GCD (Euclidean Algorithm)	Medium	Classical algorithm
9	Binary Search	Medium	Divide & conquer
10	Nested List Sum	Hard	Deep recursion with nested structures

Requirements

• Python 3.8 or newer
• Jupyter (Notebook or JupyterLab)
• Optional: VS Code with the Python and Jupyter extensions

Quick start (macOS, zsh)

1. Create and activate a virtual environment (recommended):

python3 -m venv .venv
source .venv/bin/activate
pip install --upgrade pip
pip install jupyter

2. Launch Jupyter in this folder and open the notebook:

jupyter notebook  # or: jupyter lab

3. In the UI, open practical_recursion.ipynb, then run cells top‑to‑bottom.

Open in VS Code (optional)

1. Install the "Python" and "Jupyter" extensions.
2. Open the folder, then open practical_recursion.ipynb.
3. Select the .venv interpreter if prompted and click "Run All".

Tips while learning recursion

• Start by writing a correct base case; then add the recursive case.
• Use small inputs to trace the call stack and verify the flow.
• Compare recursive vs iterative implementations to understand trade‑offs.
• Python’s default recursion depth is ~1000; deep recursion may raise RecursionError. Prefer iterative or optimized approaches, or redesign to avoid deep stacks.

Troubleshooting

• "command not found: jupyter":
  • Ensure the venv is active and run pip install jupyter.
  • If using JupyterLab, install with pip install jupyterlab and launch jupyter lab.
• VS Code can’t find kernel/interpreter:
  • Select the .venv interpreter from the top‑right kernel picker in the notebook.
• RecursionError:
  • Reduce input size, switch to an iterative approach, or apply memoization/alternative patterns.

License

This project is released under the MIT License.