Debug with pdb

Start script under the Python debugger

python3 -m pdb script.py

More python commands

Set breakpoint in code

breakpoint() # Python 3.7+ — drops into pdb at this line

Built-in breakpoint() is equivalent to import pdb; pdb.set_trace()
Run tests with pytest

pytest -x -v --tb=short tests/

Stop at first failure, verbose, short traceback
Check syntax without running

python3 -m py_compile script.py && echo OK

Compile to bytecode only to catch syntax errors
Format code with black

black --check --diff . && black .

Preview changes then apply Black formatting
Lint with ruff

ruff check . --fix

Fast linter + auto-fix (replaces flake8, isort, pyupgrade)