Re: Debugging Python

From: Harry George (harry.g.george_at_boeing.com)
Date: 01/09/04 

Date: Fri, 9 Jan 2004 10:29:46 GMT

Peter Hansen <peter@engcorp.com> writes:

> Ashley Lloyd wrote:
> >
> > What do people generally use to debug their Python programs? I haven't seen
> > anything out there that walks through the code, but perhaps I'm looking in
> > the wrong places?
>
> When I need to, which is rare, I either use print statements (a very
> solid technology dating from, oh, last century sometime ;-), or the
> Python debugger module: pdb.
>
> Actually, all I ever do with pdb is this:
>
> # this is just before the code that I think is failing
> import pdb
> pdb.set_trace()
>
> # code that I'm about to trace through goes here
>
>
> And about the only features of pdb I've had to use are "r", "n", and
> the ability to inspect arbitrary variables.
>
> I'm not sure about others, but when I design and code using test-driven
> development (TDD), I tend not to need to debug almost ever. The need
> to debug is usually when you aren't sure where a typo, or logic error,
> or other mistake has actually occurred. When using TDD, it's exceedingly
> rare that when a test fails, I don't know exactly where the problem is
> without having to resort to traditional (slow, tedious, annoying) debugging.
>
> -Peter

Interesting. A python newbie asked me the same thing yesterday and I
told him almost exactly what you said: If you are doing test-based
(whether or not it is with someojne else and thus Agile), you don't
get into those grim debug sessions that are part of life in C/C++
land.

Actually what I said was something like

"If you don't make mistakes, you don't need a debugger. The way to
avoid mistakes is to test everytime you edit a line or two of code.

"If you need to, use my homegrown debug statements (which print the
module and method/function name, the message, and then flush). If you
really get stuck, there is a debugger, but typically you just need
debuggers to solve memory problems. Python mistakes tend to be much
higher level, and pretty obvious once you see the data values." 

-- 
harry.g.george@boeing.com
6-6M31 Knowledge Management
Phone: (425) 342-5601

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