Fix a "Good First Issue"
The best way to learn a codebase is to fix something real inside it.
Key Insight
PyTorch labels some open issues "good first issue" — small, well-scoped bugs or features meant for newcomers. Fixing one walks you through the full contributor workflow: find the code, change it, test it, and open a pull request.
Why This Matters
Reading the source teaches you how PyTorch works; fixing an issue teaches you how to change it. It is the step that turns you from a user of PyTorch into a contributor to it.