How to set breakpoint in another module (don't set it on function definition line, if you want to break when function starts being executed)

Question

I'm trying to debug a module "main", which calls a function "broken_function" at line 356 of "another_module". I'm having an error in that function and want to put a breakpoint at its start. Below is the listing. Am I doing something wrong? Cause, the breakpoint doesn't work:

$ python -m pdb main (Pdb) import sys (Pdb) sys.path.append("/home/user/path/to/another/module") (Pdb) import another_module (Pdb) b another_module:356 Breakpoint 1 at /home/user/path/to/another/module/another_module.py:356 (Pdb) c Traceback (most recent call last): ... File "/home/user/path/to/another/module/another_module.py", line 383, in broken_function f=open("../jobs/temptree.tre", "r") IOError: [Errno 2] No such file or directory: '../jobs/temptree.tre' Uncaught exception. Entering post mortem debugging ... 

Answer 1

You are setting the breakpoint correctly. I imagine it is not stopping because the line of code you are breaking on is not called. Put the break on line 383.

Answer 2

You can also set the breakpoint directly with the file and line number, without having to import either sys or another_module.

(Pdb) b /home/user/path/to/another/module/another_module.py:383 Breakpoint 1 at /home/user/path/to/another/module/another_module.py:383 

Note that /home/user/path/to/another/module/another_module.py needs to be imported and line 383 needs executable and in the path of execution for it to break, as others have pointed out.

For more help, type help b (or for that matter help followed by any other command) to get more information on that command.