pythonANYbreakpointpdbinteractive
python
breakpoint()Uses Python's built-in breakpoint hook. By default this opens pdb in interactive runs.
Python Debugging Cheat Sheet
Core Python debugging commands, traceback inspection, runtime introspection, and practical troubleshooting workflows.
Export
Copy the compact sheet, download it, or print it.
Download
`D` dense toggle · `C` copy all
Breakpoints and pdb
Interactive debugging with built-in breakpoints and pdb.
pythonANYpdbset-tracebreakpoint
python
import pdb; pdb.set_trace()Useful when you want an explicit dependency-free breakpoint in scripts and older codebases.
bashANYpdbclidebugger
bash
python -m pdb app.pyStarts the debugger before the first line of the script and lets you step through execution.
bashANYpdbargumentscli
bash
python -m pdb app.py --env dev --port 8000textANYpdbstep-over
text
nIn pdb, `n` runs the current line and stops at the next line in the same frame.
textANYpdbstep-into
text
stextANYpdbcontinue
text
ctextANYpdbcontrol-flow
text
untiltextANYpdbsource-view
text
ltextANYpdbinspectvariables
text
p variable_nametextANYpdbpretty-print
text
pp complex_objecttextANYpdbstacktrace
text
wtextANYpdbframestraceback
text
u
dtextANYpdbbreakpoints
text
b app.py:42Tracebacks and Exceptions
Capture and inspect failures quickly.
pythonANYtracebackexceptionsdiagnostics
python
import traceback
try:
risky_call()
except Exception:
traceback.print_exc()pythonANYtracebacklogging
python
import traceback
try:
risky_call()
except Exception:
error_text = traceback.format_exc()pythonANYexceptionssystraceback
python
import sys
try:
risky_call()
except Exception:
exc_type, exc_value, exc_tb = sys.exc_info()pythonANYexceptionschainingdebugging
python
try:
parse_config()
except ValueError as exc:
raise RuntimeError("Invalid configuration") from excpythonANYfaulthandlercrashsegfault
python
import faulthandler
faulthandler.enable()bashANYfaulthandlercli
bash
python -X faulthandler app.pybashANYwarningsdiagnostics
bash
python -Wd app.pybashANYdev-moderuntimediagnostics
bash
python -X dev app.pyRuntime Inspection
Inspect objects, frames, environment, and imports.
pythonANYinspectionobjects
python
print(type(obj))
print(dir(obj))pythonANYinspectiondict
python
print(vars(obj))pythonANYpprintinspection
python
from pprint import pprint
pprint(payload)pythonANYinspectsignaturefunctions
python
import inspect
print(inspect.signature(func))pythonANYinspectsource
python
import inspect
print(inspect.getsource(func))pythonANYimportssys-path
python
import sys
for path in sys.path:
print(path)pythonANYimportsmodule-resolution
python
import package_name
print(package_name.__file__)pythonANYenvironmentconfiguration
python
import os
print(os.environ.get("APP_ENV"))Logging and Diagnostics
Use structured, actionable logs for faster debugging.
pythonANYloggingdebug
python
import logging
logging.basicConfig(level=logging.DEBUG)
logging.debug("Starting debug run")pythonANYloggingformat
python
import logging
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s %(levelname)s %(name)s %(message)s',
)pythonANYloggingexceptionstraceback
python
import logging
logger = logging.getLogger(__name__)
try:
risky_call()
except Exception:
logger.exception("Request processing failed")pythonANYloggingcontext
python
import logging
base_logger = logging.getLogger(__name__)
logger = logging.LoggerAdapter(base_logger, {"request_id": request_id})
logger.info("Processing request")pythonANYtimingperformance
python
import time
start = time.perf_counter()
result = expensive_call()
elapsed = time.perf_counter() - start
print(f"Elapsed: {elapsed:.4f}s")bashANYtimeitbenchmark
bash
python -m timeit "sum(range(1000))"pytest and unittest Debugging
Debug tests and isolate flaky or failing behavior.
bashANYpytestfail-fast
bash
pytest -xbashANYpytestpdb
bash
pytest --pdbbashANYpyteststdoutcapture
bash
pytest -sbashANYpytesttargeted-run
bash
pytest tests/test_api.py::test_create_userbashANYpytestlast-failed
bash
pytest --lfbashANYpytesttracebackslocals
bash
pytest -vv --showlocalsbashANYunittestverbose
bash
python -m unittest -v tests.test_serviceProfiling and Memory
Distinguish slow code from broken code and inspect resource usage.
bashANYcprofileprofiling
bash
python -m cProfile app.pybashANYcprofileperformance
bash
python -m cProfile -s tottime app.pypythonANYcprofilein-process
python
import cProfile
import pstats
profiler = cProfile.Profile()
profiler.enable()
expensive_call()
profiler.disable()
pstats.Stats(profiler).sort_stats('tottime').print_stats(20)pythonANYmemorytracemalloc
python
import tracemalloc
tracemalloc.start()
# run code
snapshot = tracemalloc.take_snapshot()
for stat in snapshot.statistics('lineno')[:10]:
print(stat)pythonANYpsutilmemorycpu
python
import os
import psutil
process = psutil.Process(os.getpid())
print(process.memory_info())
print(process.cpu_percent(interval=1.0))Requires the third-party `psutil` package, but it is extremely useful for production debugging and local diagnostics.
Async, Web, and Production Troubleshooting
Common debugging patterns for servers, workers, and async code.
bashANYasynciodebug-mode
bash
PYTHONASYNCIODEBUG=1 python app.pypythonANYasynciodebug
python
import asyncio
async def main():
...
asyncio.run(main(), debug=True)bashANYhttp-serverrepro
bash
python -m http.server 8000bashANYimportsstartupperformance
bash
python -X importtime app.pypythonANYthreadssignalshung-process
python
import faulthandler
import signal
faulthandler.register(signal.SIGUSR1)After registering a signal, send `SIGUSR1` to the process to dump thread stack traces.
More in Python Debugging
Python Profiling and Troubleshooting Cheat Sheet
Profile Python programs, inspect memory and imports, and diagnose slow or stuck processes.
Python Test Debugging Cheat Sheet
pytest and unittest debugging patterns for isolating failures, flaky tests, fixtures, and CI-only issues.
Python Logging and Tracing Cheat Sheet
Reference for Python logging, stack traces, warning visibility, trace hooks, and instrumentation patterns.
Python pdb and Breakpoint Cheat Sheet
Focused reference for pdb commands, breakpoints, stepping, stack frames, and conditional debugging.