PEP 8 style enforcing program

[montyphyton at gmail.com]

Some recent posts about Python programming style got me thinking.
Since we have the PEP 8 which gives some guidelines about the style to
be used, do we have any program that can check for violations of these
guidelines within the source code? I understand that there are a lot
of code beautifiers out there, but i haven't seen one specially
tailored for Python... Is there even a desire in Python community for
a program like this (by Python community I mean the people in this
group:) ) ? I think it would be a nice little project for practice and
I'd like to do it, but if there is already something like this then I
can probably spend my time on something more productive. So, I'd like
to hear your opinion on this...
There is one thing that I don't understand about PEP 8 - why is using
spaces considered more desirable than using tabs for indentation?