Debugging practice pieces

Learning to debug code is a critical skill in programming; debugging is one of the major components of any programmer's job. These practice pieces will both introduce classic errors, but also techniques for dealing with them.

1. Getting it working / decomposition.
2. Understanding messages from Python; see also this list of classic messages.
3. Close reading.
4. Using print.
5. Using the debugger.
6. At this stage, check out this list of practical advice on solving issues.
7. Type hints.
8. Using a profiler.
9. Documentation.
10. Doctests.
11. Unit tests.
12. Code management.
13. Continuous integration.