Suggestions for Python debugging tools?

Question

Yesterday I made a simulation using Python. I had a few difficulties with variables and debugging.

Is there any software for Python, which provides a decent debugger?

Related question: What is the best way to debug my Python code?

Answer 1

Don't forget about post-mortem debugging! After an exception is thrown, the stack frame with all of the locals is contained within sys.last_traceback. You can do pdb.pm() to go to the stack frame where the exception was thrown then p(retty)p(rint) the locals().

Here is a function that uses this information to extract the local variables from the stack.

def findlocals(search, startframe=None, trace=False):

    from pprint import pprint
    import inspect, pdb

    startframe = startframe or sys.last_traceback
    frames = inspect.getinnerframes(startframe)

    frame = [tb for (tb, _, lineno, fname, _, _) in frames
             if search in (lineno, fname)][0]

    if trace:
        pprint(frame.f_locals)
        pdb.set_trace(frame)
    return frame.f_locals

Usage:

>>> def screwyFunc():
    a = 0
    return 2/a

>>> screwyFunc()

Traceback (most recent call last):
  File "<pyshell#62>", line 1, in <module>
    screwyFunc()
  File "<pyshell#55>", line 3, in screwyFunc
    return 2/a
ZeroDivisionError: integer division or modulo by zero
>>> findlocals('screwyFunc')
{'a': 0}