[Python-Dev] pprint(iterator)

[Aahz]

On Tue, Jan 27, 2009, Raymond Hettinger wrote:
>
> It is becoming the norm in 3.x for functions to return iterators,
> generators, or views whereever possible.
>
> I had a thought that pprint() ought to be taught to print iterators:
>
>    pprint(enumerate(seq))
>    pprint(map(somefunc, somedata))
>    pprint(permutations(elements))
>    pprint(mydict.items())

Along the lines of what others have said: pprint() cannot consume an
unknown iterator.  Therefore, you can pretty up the existing output
slightly or special-case certain known iterators.  There might also be an
API change to pprint() that allowed it to consume iterators.

The reason I'm chiming in is that I would welcome a PEP that created a
__pprint__ method as an alternative to special-casing.  I think that it
would be generically useful for user-created objects, plus once you've
added this feature other people can easily do some of the grunt work of
extending this through the Python core.  (Actually, unless someone
objects, I don't think a PEP is required, but it would be good for the
usual reasons that PEPs are written, to provide a central place
documenting the addition.)

This can also be done for Python 2.7, too.
-- 
Aahz (aahz at pythoncraft.com)           <*>         http://www.pythoncraft.com/

Weinberg's Second Law: If builders built buildings the way programmers wrote 
programs, then the first woodpecker that came along would destroy civilization.