On Feb 06, 2010, at 11:22 PM, exarkun@twistedmatrix.com wrote:
I haven't tried to repro this particular example, but the reason is that we don't want to have to call getpwd() on every import nor do we want to have some kind of in-process variable to cache the current directory. (getpwd() is relatively slow and can sometimes fail outright, and trying to cache it has a certain risk of being wrong.)
Assuming you mean os.getcwd():
exarkun@boson:~$ python -m timeit -s 'def f(): pass' 'f()' 10000000 loops, best of 3: 0.132 usec per loop exarkun@boson:~$ python -m timeit -s 'from os import getcwd' 'getcwd()' 1000000 loops, best of 3: 1.02 usec per loop exarkun@boson:~$ So it's about 7x more expensive than a no-op function call. I'd call this pretty quick. Compared to everything else that happens during an import, I'm not convinced this wouldn't be lost in the noise. I think it's at least worth implementing and measuring.
I'd like to see the effect on command line scripts that are run often and then exit, e.g. Bazaar or Mercurial. Start up time due to import overhead seems to be a constant battle for those types of projects. -Barry