Raymond, there are very compelling timings/benchmarks for this -- not so much the original issue here (generator vs list, that's not really an issue) but having a scandir() function that returns the stat-like info from the OS so you don't need extra stat calls. This speeds up os.walk() by 7-20 times on Windows and 4-5 times on Linux. See more at: https://github.com/benhoyt/scandir#benchmarks

I've written a draft PEP that I've sent to the PEP editors (if you're interested, it's at https://github.com/benhoyt/scandir/blob/master/PEP.txt). If any of the PEP editors are listening here ... would love some feedback on that at some stage. :-)

Victor -- development has started outside the stdlib here: https://github.com/benhoyt/scandir and PyPI module here: https://pypi.python.org/pypi/scandir Both are being used by various people.