[Python-Dev] Startup time (original) (raw)

Alex Martelli aleax@aleax.it
Wed, 7 May 2003 22:57:26 +0200

On Wednesday 07 May 2003 09:05 pm, Skip Montanaro wrote:

Jeff> In encodings.init.py, the only use of re is for the Jeff> normalizeencoding function. It could potentially be replaced with only Jeff> string operations: ... Jeff> .. or the import of re could be moved inside normalizeencoding.

I don't know if this still holds true, but at one point during the 2.x series I think it was pretty expensive to perform imports inside functions, much more expensive than in 1.5.2 at least (maybe right after nested scopes were introduced?). If that is still true, moving the import might be false economy.

Doesn't seem to be true in 2.3, if I understand what you're saying:

[alex@lancelot src]$ python Lib/timeit.py -s'def f(): pass' 'import math; f()' 100000 loops, best of 3: 4.04 usec per loop

[alex@lancelot src]$ python Lib/timeit.py -s'def f(): import math' 'pass; f()' 100000 loops, best of 3: 4.05 usec per loop

or even

[alex@lancelot src]$ python Lib/timeit.py -s'import math' -s'def f(): pass' 'reload(math); f()' 10000 loops, best of 3: 168 usec per loop

[alex@lancelot src]$ python Lib/timeit.py -s'import math' -s'def f(): reload(math)' 'pass; f()' 10000 loops, best of 3: 169 usec per loop

Alex