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Merged
AA-Turner merged 6 commits into from
Apr 24, 2025
Merged

gh-118761: Optimise import time for shlex#132036

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1fd83f1
Optimise import time for ``shlex``
AA-Turner Apr 2, 2025
8811463
Revert deferral of sys and io
AA-Turner Apr 4, 2025
bd6916a
Switch to bytes.translate() based approach
AA-Turner Apr 6, 2025
192329e
Update Lib/shlex.py
AA-Turner Apr 18, 2025
cc130af
Merge branch 'main' into opt-shlex
AA-Turner Apr 18, 2025
4a640ce
Add test_lazy_imports
AA-Turner Apr 21, 2025
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17 changes: 10 additions & 7 deletions Lib/shlex.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,11 +7,7 @@
# iterator interface by Gustavo Niemeyer, April 2003.
# changes to tokenize more like Posix shells by Vinay Sajip, July 2016.

import os
import re
import sys
from collections import deque

from io import StringIO

__all__ = ["shlex", "split", "quote", "join"]
Expand All@@ -20,6 +16,8 @@ class shlex:
"A lexical analyzer class for simple shell-like syntaxes."
def __init__(self, instream=None, infile=None, posix=False,
punctuation_chars=False):
from collections import deque # deferred import for performance

if isinstance(instream, str):
instream = StringIO(instream)
if instream is not None:
Expand DownExpand Up@@ -278,6 +276,7 @@ def read_token(self):

def sourcehook(self, newfile):
"Hook called on a filename to be sourced."
import os.path
if newfile[0] == '"':
newfile = newfile[1:-1]
# This implements cpp-like semantics for relative-path inclusion.
Expand DownExpand Up@@ -318,13 +317,17 @@ def join(split_command):
return ' '.join(quote(arg) for arg in split_command)


_find_unsafe = re.compile(r'[^\w@%+=:,./-]', re.ASCII).search

def quote(s):
"""Return a shell-escaped version of the string *s*."""
if not s:
return "''"
if _find_unsafe(s) is None:

# Use bytes.translate() for performance
safe_chars = (b'%+,-./0123456789:=@'
b'ABCDEFGHIJKLMNOPQRSTUVWXYZ_'
b'abcdefghijklmnopqrstuvwxyz')
# No quoting is needed if `s` is an ASCII string consisting only of `safe_chars`
if s.isascii() and not s.encode().translate(None, delete=safe_chars):
return s

# use single quotes, and put single quotes into double quotes
Expand Down
4 changes: 4 additions & 0 deletions Lib/test/test_shlex.py
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Original file line numberDiff line numberDiff line change
Expand Up@@ -3,6 +3,7 @@
import shlex
import string
import unittest
from test.support import import_helper


# The original test data set was from shellwords, by Hartmut Goebel.
Expand DownExpand Up@@ -363,6 +364,9 @@ def testPunctuationCharsReadOnly(self):
with self.assertRaises(AttributeError):
shlex_instance.punctuation_chars = False

def test_lazy_imports(self):
import_helper.ensure_lazy_imports('shlex',{'collections', 're', 'os'})


# Allow this test to be used with old shlex.py
if not getattr(shlex, "split", None):
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2025-04-03-00-56-48.gh-issue-118761.Vb0S1B.rst
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@@ -0,0 +1,3 @@
Improve import times by up to 33x for the :mod:`shlex` module,
and improve the performance of :func:`shlex.quote` by up to 12x.
Patch by Adam Turner.
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