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title Python Debugpy
verification metadata-normalized
source skill-pipeline
status draft
created 2026-05-09

背景

（此 lesson 从 skill python-debugpy 自动提取，待补全）

根因

（待补充）

修复

Python Debugger (pdb + debugpy)

Overview

Three tools, picked by situation:

Tool When
breakpoint() + pdb Local, interactive, simplest. Add breakpoint() in the source, run normally, get a REPL at that line.
python -m pdb Launch an existing script under pdb with no source edits. Useful for quick poking.
debugpy Remote / headless / "attach to already-running process." Talks DAP, scriptable from terminal, works for long-lived processes (gateway, daemon, PTY children).

Start with breakpoint(). It's the cheapest thing that works.

When to Use

  • A test fails and the traceback doesn't reveal why a value is wrong
  • You need to step through a function and watch a collection mutate
  • A long-running process (hermes gateway, tui_gateway) misbehaves and you can't restart it
  • Post-mortem: an exception fired in prod-ish code and you want to inspect locals at the crash site
  • A subprocess / child (Python _SlashWorker, PTY bridge worker) is the actual bug site

Don't use for: things print() / logging.debug solve in under a minute, or things pytest -vv --tb=long --showlocals already reveals.

pdb Quick Reference

Inside any pdb prompt ((Pdb)):

Command Action
h / h cmd help
n next line (step over)
s step into
r return from current function
c continue
unt N continue until line N
j N jump to line N (same function only)
l / ll list source around current line / full function
w where (stack trace)
u / d move up / down in the stack
a print args of the current function
p expr / pp expr print / pretty-print expression
display expr auto-print expr on every stop
b file:line set breakpoint
b func break on function entry
b file:line, cond conditional breakpoint
cl N clear breakpoint N
tbreak file:line one-shot breakpoint
!stmt execute arbitrary Python (assignments included)
interact drop into full Python REPL in current scope (Ctrl+D to exit)
q quit

The interact command is the most powerful — you can import anything, inspect complex objects, even call methods that mutate state. Locals are read-only by default; use !x = 42 from the (Pdb) prompt to mutate.

Recipe 1: Local breakpoint

Easiest. Edit the file:

def compute(x, y):
    result = some_helper(x)
    breakpoint()           # <-- drops into pdb here
    return result + y

Run the code normally. You land at the breakpoint() line with full access to locals.

Don't forget to remove breakpoint() before committing. Use git diff or a pre-commit grep:

rg -n 'breakpoint\(\)' --type py

Recipe 2: Launch a script under pdb (no source edits)

python -m pdb path/to/script.py arg1 arg2
# Lands at first line of script
(Pdb) b path/to/script.py:42
(Pdb) c

Recipe 3: Debug a pytest test

The herm

验证

（待补充）