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pdb Module¶

The pdb module provides an interactive debugger for Python code, allowing breakpoints, stepping, and inspection of variables.

Complexity Reference¶

Operation	Time	Space	Notes
`set_trace()`	Varies	O(1)	Setup is O(1); interactive runtime is program/user dependent
Breakpoint	O(1) to register	O(1)	Hit checks occur during program execution
Step/continue	Varies	O(1)	Runs until next stop; depends on code executed

Interactive Debugging¶

Setting Breakpoints¶

import pdb

def buggy_function(x):
    # Enter debugger (setup is O(1); runtime depends on program/user)
    pdb.set_trace()

    result = x * 2
    return result

# When called, drops into interactive debugger
# Commands: n=next, s=step, c=continue, l=list, p=print

Post-Mortem Debugging¶

import pdb
import traceback

try:
    1 / 0
except Exception:
    # Debug after exception (setup is O(1); runtime depends on session)
    pdb.post_mortem()