python · AA-Turner · Apr 24, 2025 · Apr 2, 2025 · Apr 4, 2025 · Apr 6, 2025
diff --git a/Lib/shlex.py b/Lib/shlex.py
@@ -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"]
@@ -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:
@@ -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.
@@ -318,7 +317,14 @@ def join(split_command):
    return ' '.join(quote(arg) for arg in split_command)


-_find_unsafe = re.compile(r'[^\w@%+=:,./-]', re.ASCII).search
+def _find_unsafe(s, /):
+    # this function replaces itself with the compiled pattern on execution,
+    # to allow as deferred import of re for performance
+    global _find_unsafe
+    import re
+    _find_unsafe = re.compile(r'[^\w@%+=:,./-]', re.ASCII).search
+    return _find_unsafe(s)
+

 def quote(s):
    """Return a shell-escaped version of the string *s*."""

diff --git a/Misc/NEWS.d/next/Library/2025-04-03-00-56-48.gh-issue-118761.Vb0S1B.rst b/Misc/NEWS.d/next/Library/2025-04-03-00-56-48.gh-issue-118761.Vb0S1B.rst
@@ -0,0 +1,2 @@
+Improve import times by up to 33x for the :mod:`shlex` module. Patch by Adam
+Turner.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Improve import times by up to 33x for the :mod:`shlex` module. Patch by Adam
		Turner.