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gh-118761: Improve import time of `mimetypes` by hugovk · Pull Request #126979 · python/cpython · GitHub

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gh-118761: Improve import time of mimetypes #126979

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hugovk merged 4 commits into from
Nov 21, 2024
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gh-118761: Improve import time of mimetypes #126979

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4069061
Improve import time of mimetypes: defer urllib.parse
hugovk Nov 18, 2024
12fc4fe
Update link redirect
hugovk Nov 18, 2024
e6e4752
Improve import time of mimetypes: defer os, sys, posixpath
hugovk Nov 18, 2024
0f2ccf0
Add blurb
hugovk Nov 18, 2024
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22 changes: 16 additions & 6 deletions Lib/mimetypes.py
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Expand Up @@ -23,11 +23,6 @@
read_mime_types(file) -- parse one file, return a dictionary or None
"""

import os

danielhollas Nov 19, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

I wonder if lazy import of os module is worth it here, it is needed three times and the improvement is small and only in a special case.

vstinner Nov 19, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Python always imports os and sys at startup. Moving import sys makes sense, it's only used by _main(). But I'm not sure about moving os.

danielhollas Nov 19, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

In the OP, @hugovk provides timings for when the python is run without the site.py module (python -S), in which case os and sys are not loaded I believe?

hugovk Nov 21, 2024

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Yes, it makes a difference with python -S, compare the last three images above.

But I'm fine reverting any of these, because I expect with site.py is by far the most usual thing.
import sys
import posixpath
import urllib.parse

try:
from _winapi import _mimetypes_read_windows_registry
except ImportError:
Expand Down Expand Up @@ -119,6 +114,10 @@ def guess_type(self, url, strict=True):
Optional 'strict' argument when False adds a bunch of commonly found,
but non-standard types.
"""
# Lazy import to improve module import time
import os
import urllib.parse

# TODO: Deprecate accepting file paths (in particular path-like objects).
url = os.fspath(url)
p = urllib.parse.urlparse(url)
Expand Down Expand Up @@ -146,13 +145,20 @@ def guess_type(self, url, strict=True):
if '=' in type or '/' not in type:
type = 'text/plain'
return type, None # never compressed, so encoding is None

# Lazy import to improve module import time
import posixpath

return self._guess_file_type(url, strict, posixpath.splitext)

def guess_file_type(self, path, *, strict=True):
"""Guess the type of a file based on its path.

Similar to guess_type(), but takes file path instead of URL.
"""
# Lazy import to improve module import time
import os

path = os.fsdecode(path)
path = os.path.splitdrive(path)[1]
return self._guess_file_type(path, strict, os.path.splitext)
Expand Down Expand Up @@ -399,6 +405,9 @@ def init(files=None):
else:
db = _db

# Lazy import to improve module import time
import os

for file in files:
if os.path.isfile(file):
db.read(file)
Expand Down Expand Up @@ -445,7 +454,7 @@ def _default_mime_types():
}

# Before adding new types, make sure they are either registered with IANA,
# at http://www.iana.org/assignments/media-types
# at https://www.iana.org/assignments/media-types/media-types.xhtml
# or extensions, i.e. using the x- prefix

# If you add to these, please keep them sorted by mime type.
Expand Down Expand Up @@ -637,6 +646,7 @@ def _default_mime_types():

def _main():
import getopt
import sys

USAGE = """\
Usage: mimetypes.py [options] type
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2024-11-18-22-02-47.gh-issue-118761.GQKD_J.rst
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@@ -0,0 +1,2 @@
Improve import time of :mod:`mimetypes` by around 11-16 times. Patch by Hugo
van Kemenade.
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