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22. Debugging with pdb

Python includes a built-in debugger module called pdb for interactive debugging.

Running a Script with pdb​

python -m pdb script.py

Inserting a Breakpoint​

import pdb; pdb.set_trace()

x = 10
y = 20
z = x + y  # execution will pause here

Common pdb Commands​

  • n: next line
  • s: step into function
  • c: continue execution
  • q: quit debugger
  • p var: print variable value

Practice Challenge​

Debug a function that incorrectly calculates the factorial of 5. Use pdb to step through and find the bug.

Wrap-Up​

pdb provides an interactive way to inspect program state step by step.