Save/restore breakpoints between pdb runs

dieter dieter at
Sat Jul 12 08:05:27 CEST 2014

Ed Blackman <ed at> writes:
> I've recently started using Python for my job (as opposed to writing
> smallish scripts for personal use), and so have needed to debug quite
> a bit more.
> I've been using pdb mainly via 'python -m pdb script args'.  Perhaps
> it's my Java background, but even when I have permissions to change
> the source, I find editing source to insert 'import pdb;
> pdb.set_trace()' unnatural.  The consequence is that I have to
> recreate my breakpoints when I have to exit pdb.
> I've written the following code, which I load from .pdbrc with
> 'execfile(os.path.expanduser('~/'))'

This approach does not seem very robust to me:

  "pdb" resolves all breakpoints to lines (in source files) - and
  any modification to the source may change the lines.
  As a consequence, your breakpoints may no longer be at the
  places where you expect them.

A long time ago, I have developped "dm.pdb" - a slight
extension/improvement over "pdb". One of the extensions
has been to make it possible to set breakpoints from outside
the debugger -- without too many surprises. It looks somehow like that:

  from dm.pdb import Pdb; D = Pdb()
  from ... import f
  from ... import g
  from ... import C
  D.do_break("f") # set breakpoint on "f"
  D.do_break("g") # set breakpoint on "g"
  D.do_breack("C.m") # set breakpoint on method "m" of class "C"

It is more robust than breakpoints on line numbers - but, of course,
it cannot be automated but must be targeted to individual programs.
In addition, the robustness is limited to breakpoints on
executable objects; setting breakpoints on line numbers is possible, too --
but has the same problem with moving lines.

In the meantime, "pdb" itself may support this form of external
control (maybe even better then "dm.pdb").

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