debugging in python

Question

i am using the python shell to try to do debugging

i set a breakpoint

i did:

>>> import pdb
>>> import mymodule
>>> pdb.run('mymodule.test()')

but it is just running my program without stopping at the breakpoint!

what am i donig wrong?

Answer 1

The typical usage to break into the debugger from a running program is to insert

import pdb; pdb.set_trace()

at the location you want to break into the debugger. You can then step through the code following this statement, and continue running without the debugger using the c command.

The typical usage to inspect a crashed program is:

>>> import pdb
>>> import mymodule
>>> mymodule.test()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "./mymodule.py", line 4, in test
    test2()
  File "./mymodule.py", line 3, in test2
    print spam
NameError: spam
>>> pdb.pm()
> ./mymodule.py(3)test2()
-> print spam
(Pdb)

The Python site offers a very elaborate tutorial for pdb. Go to http://docs.python.org/library/pdb.html.

Answer 2

How did you set a breakpoint? Try adding the line in your code:

import pdb
pdb.set_trace()

and then run it. If you're in the pdb shell, then "break foo.py:45" will break on line 45 of file foo.py.

Here are some useful commands:

h    help, list commands
s    step through current line
n    step to next line
u    go up the stack
c    continue execution

Check the full list by typing 'h'. And "help X" will give you help on command X. Also, see this tutorial:

• Interactive Debugging in Python