Changes by Serhiy Storchaka storch...@gmail.com:
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resolution: - fixed
stage: patch review - committed/rejected
status: open - closed
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Python tracker rep...@bugs.python.org
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Daniel Holth added the comment:
Thanks. I guess I know who to ask now.
It was just painful seeing so much import-time computation, pretty much
guaranteed to happen every time Python starts up, being wasted on a
feature that is rarely used. On the Raspberry Pi the majority of the
import time is
Larry Hastings added the comment:
Since this isn't a bugfix, it was inappropriate to check this in after
feature-freeze for 3.4. However it looks harmless enough, so I'm not asking
you to revert it at this time.
I guess it's easier to get forgiveness than permission, huh.
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nosy:
Daniel Holth added the comment:
Fixed in http://hg.python.org/cpython/rev/536a2cf5f1d2
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Daniel Holth added the comment:
I am withdrawing zipfile-no-crc32.patch. It did not work correctly.
zdlazy.patch should go in. It avoids creating the rarely-needed crc32 table
until the first time it is needed, saving some memory and the majority of time
needed to import the module.
Serhiy Storchaka added the comment:
I meant my pure Python patch in issue10030. Binding crctable to local variable
is one of microoptimizations. Not the largest one however. So in general I not
objects. Your patch LGTM. Only one nitpick -- instead not
_ZipDecrypter.crctable use
Serhiy Storchaka added the comment:
The objection to zipfile-no-crc32.patch is that binascii.crc32() and _crc32()
have different signatures. binascii.crc32() accepts a byte object while
_crc32() accepts a single integer. With packing this value into a bytes object
_crc32() will be much
New submission from Daniel Holth:
http://hg.python.org/cpython/file/e7305517260b/Lib/zipfile.py#l460
I noticed this table taking up time on import. I'd guess that it pre-dates
zlib.crc32 which is imported at the top of the file. I also suspect that most
of the time this table isn't even used
Daniel Holth added the comment:
Someone who has a better understanding of zipfile may be able to get
zlib.crc32(bytes[ch], running_crc) to work correctly. This patch that passes
the zipfile tests generates the crctable only when _ZipDecrypter() is
instantiated.
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Added file:
Changes by Serhiy Storchaka storch...@gmail.com:
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components: +Library (Lib)
nosy: +alanmcintyre, loewis, serhiy.storchaka
stage: - patch review
type: - performance
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Serhiy Storchaka added the comment:
How much time take it?
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Daniel Holth added the comment:
It takes 706 microseconds.
On my machine
%timeit import sys; del sys.modules['zipfile']; import zipfile import
zipfile
takes 2.51 ms without the patch and 1.7 ms with the patch.
On Sat, Jul 20, 2013, at 12:13 PM, Serhiy Storchaka wrote:
Serhiy Storchaka
Daniel Holth added the comment:
I tried it on a raspberry pi. zipfile takes 36 ms to import and 10 ms if it
does not generate the crctable.
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