[Python-Dev] displayhook behavior in pdb

[Guido van Rossum]

On Wed, Sep 16, 2009 at 3:48 AM, Paul Moore <p.f.moore at gmail.com> wrote:

> 2009/9/16 Michael Foord <fuzzyman at voidspace.org.uk>:
> > Georg Brandl wrote:
> >>
> >> May I have a short vote on this issue:
> >>
> >>   http://bugs.python.org/issue6903
> >>
> >> In short, pdb (since 2.6) uses a separate displayhook in order to avoid
> >> _ being reassigned (which screws up debugging apps that use _ as
> gettext).
> >> In that displayhook, I did not add the suppression of printing None, as
> >> it can be confusing to look at variables and get no output:
> >>
> >> (Pdb) foo
> >> 1
> >> (Pdb) bar
> >> (Pdb)
> >>
> >> (You could argue that this is what the "p" command is for though.)
> >>
> >> Now in Python 3, where print is a function, if you call print in a loop
> >> (e.g. to debug a list or dictionary, as it is advertised in the pdb docs
> >> under the "alias" command), the output has the printed values
> interspersed
> >> with "None"s.
> >>
> >> Now, what is the lesser evil?
> >>
> >>
> >
> > IMO not showing the extraneous Nones is preferable.
>
> I agree (although I don't use pdb, so my view shouldn't be given too
> much weight...)
>

I *do* use pdb a lot, and I agree that the new behavior is weird.

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)
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