Tell me about a Python project you built. What problem did it solve and what would you do differently?

Note: Pick the project with the most interesting constraint, not the one with the most lines. Interviewers are listening for judgement, not scope.

Give it in four beats:

• The problem in business terms. "A nightly reconciliation that took four hours and blocked the finance team" lands far better than "an ETL pipeline".
• Your actual contribution. Be precise about what you wrote versus what existed. Inflating this is trivially exposed by one follow-up question.
• The hard part. Strong candidates: memory blowing up on a large dataset, a third-party API that rate-limited you, making a long job restartable after a failure, or a dependency conflict that forced a packaging decision.
• What you would change. Say something real — that you would have written the tests first, chosen a queue instead of threads, or used generators rather than loading everything into a list.