[Python-Dev] Proposed PEP: Optimizing Global Variable and Attribute Access
skip at pobox.com
Wed Aug 15 01:25:51 CEST 2001
Roman> Well, I just think that probably interpreter could optimize by
Roman> just IMPLICITLY making caching of global references, like in this
Roman> (current) optimization trick:
Roman> import os # for constants
Roman> def f(x, y, z, # normal atts
Roman> cached_os_O_NONBLOCK=os.O_NONBLOCK, # optimization trick
Roman> cached ....
Roman> # here we use os.O_NONBLOCK, but interpreter uses
Roman> # local _names_ and thus fast lookup.
No, that's not possible in the general case. You are assuming that
os.O_NONBLOCK is truly a constant. There's nothing to prevent me from
having this code:
i = 1
for j in range(1000):
if i % 100 == 0:
i += 1
If you simply cache the value of the global variable i, you'll never print
For those people on python-list who have no idea what this thread is about,
please be patient. Once Barry Warsaw assigns a PEP number to it, I will
announce it to python-list.
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