[Python-Dev] Withdrawn PEP 288 and thoughts on PEP 342

[Raymond Hettinger]

[Joachim Koenig-Baltes]
> > My use case for this is a directory tree walking generator that
> > yields all the files including the directories in a depth first
manner.
> > If a directory satisfies a condition (determined by the caller) the
> > generator shall not descend into it.
> >
> > Something like:
> >
> > DONOTDESCEND=1
> > for path in mywalk("/usr/src"):
> >     if os.path.isdir(path) and os.path.basename(path) == "CVS":
> >         continue DONOTDESCEND
> >     # do something with path
> >
> > Of course there are different solutions to this problem with
callbacks
> > or filters but i like this one as the most elegant.


[Donovan Baarda]
> I have implemented almost exactly this use-case using the standard
> Python generators, and shudder at the complexity something like this
> would introduce.
> 
> For me, the right solution would be to either write your own generator
> that "wraps" the other generator and filters it, or just make the
> generator with additional (default value) parameters that support the
> DONOTDECEND filtering.
> 
> FWIW, my usecase is a directory comparison generator that walks two
> directorys producing tuples of corresponding files. It optionally will
> not decend directories in either tree that do not have a corresponding
> directory in the other tree. See;
> 
> http://minkirri.apana.org.au/~abo/projects/utils/


Thank both of you for the excellent posts.  This is exactly kind of
feedback and analysis that will show whether continue EXPR is worth it.


Raymond