Nicole Zuckerman - The Glory of pdb's set_trace

Everyone needs to debug code, and it can take up a non-trivial portion of our time to wait for code to complete execution and write print messages to stdout. There’s one function in particular in the python debugger (pdb) library that can give you a much clearer understanding of what’s going on in your code, much more quickly; pdb.set_ trace(). In this talk, we’ll identify the most useful things you can do when you use set trace, that can make debugging exponentially more efficient and enjoyable.

https://us.pycon.org/2017/schedule/presentation/753/

Transcript

1. Debugging with pdb.set_trace() Nicole Zuckerman Clover Health @zuckerpunch
2. What is PDB?
3. From the docs: Or:
4. What is this set_trace() that you’re doing a whole talk about?
5. set_trace(), in action
6. But I already have print statements. What more do I need?
7. What’s so great about set_trace()? 1. Inspect contents of variables during real-time execution 2. Traverse call frames 3. Travel through execution order 4. Change live code during execution
8. Code sample time
9. Inspect contents of variables during execution
10. Inspect contents of variables during execution Inspecting arguments of currently paused function:
11. Inspect Variables continued: print/pretty print
12. Inspect Variables continued: print/pretty print
13. Inspect Variables continued: print/pretty print
14. Inspect Variables continued: print/pretty print
15. Traverse frames in call stack
16. Traverse Call Frames
17. Traverse Call Frames
18. Traverse Call Frames
19. Traverse Call Frames
20. Traverse Call Frames
21. Travel through execution
22. Traveling through execution
23. Traveling through execution
24. Traveling through execution
25. Where the heck am I, anyway?
27. List: The Fancy Parts
28. Change live code during execution
29. Changing live code during execution
30. PDB-adjacent coolness: my_thing.__dict__
31. PDB-adjacent coolness: dir(my_thing)
32. PDB-adjacent coolness: dir(my_thing)
33. Pdb gotchas
34. Gotchas pdb commands versus statements
35. Gotchas
36. Gotchas The Enter key
37. Bonus! Post-mortem debugging
38. Code sample with exception-inducing bug
39. Post-mortem at work
40. Breakpoints
41. Break!
42. Break!
43. Clear!
45. https://docs.python.org/2/library/pdb.html Questions