Build a URL Shortener (Python)

Build a working URL shortener from scratch in Python - the data model, short-code generation, and lookup - running right in your browser, no setup.

1. The Plan and the Data Model Pin down what a URL shortener actually does, then build the dictionary store that remembers one short code's long URL.
2. Making Short Codes Turn a counting number into a compact base62 short code, using a counter so every link gets a unique, collision-free label.
3. Store and Resolve Join the store and the generator into shorten() and resolve(), handling unknown codes and the same URL submitted twice.
4. A Tiny CLI, and Where to Take It Wrap shorten() and resolve() in a small command loop you can drive with typed commands, then map out how to grow it into a real service.