How do you get oriented in a big Python repo?

Don’t try to read the whole thing from top to bottom. Pick one concrete task or user-visible behavior, run the project if you can, then trace that one path from its entry point. Tests and a debugger can show which code actually runs, while the rest can wait.

I’d start with the README, project configuration, and directory layout, then look for the public entry points: a command-line script, application startup, or documented API. After that, use your editor’s search and go-to-definition tools to follow calls. A small diagram or a few notes about key modules can keep the connections from becoming a blur.

If someone knows the project, ask them for a quick architecture tour and one example of a feature moving through the code. Even a rough explanation gives you a useful starting point. If nobody is available, tests can serve as examples of intended behavior, and nearby code may reveal the conventions the project uses.

Before changing anything, get specific about the outcome you need. Find a similar feature or code path and follow its pattern, rather than making broad changes based on a guessed understanding of the whole system. Run the relevant tests before and after, then add or adjust a focused test for your change.

Some repositories are genuinely difficult to understand, especially if the structure and tests are thin. You don’t need a complete mental model to make progress. Keep track of what you’ve verified, follow one dependency chain at a time, and be willing to ask whether a confusing area is poorly organized rather than assuming you’re missing something obvious.