Debugging running Python scripts with PDB via GDB

I like to add this function to my Python scripts so that I can drop into pdb by sending a signal:

    import signal

    def sigusr1_handler(signum, stack):
        breakpoint()

    signal.signal(signal.SIGUSR1, sigusr1_handler)

And then I can drop into pdb by sending a signal:

    $ kill -s sigusr1 $PID

I also want to highlight something non-obvious about debugging mixed native and Python code. Because Python is interpreted, it is possible to run both gdb and pdb on a process at the same time, and set breakpoints using both, without issue. This can be really nice when you're working on Python bindings.

i was one of the lucky 10,000 that discovered pdb a year ago. jsut wanted to point out that you can alias your normal `python` command to run `python -m pdb -c c` and it will always run in pdb mode for most development https://twitter.com/jeremyphoward/status/1756541454288396402

You can also inspect python frames, objects/variables etc directly from GDB: https://docs.python.org/3/howto/gdb_helpers.html

Probably worth mention madbg⁽¹⁾, a fully-featured remote and preemptive debugger for Python with both a CLI and an API, that allows attaching to running programs preemptively (but does not require gdb).

⁽¹⁾https://github.com/kmaork/madbg