gh-156363: Speed up import of rlcompleter by deferring inspect and re

rlcompleter imported inspect and re at module scope, but each is used in
exactly one completion method (inspect in Completer._callable_postfix, re
in Completer.attr_matches).  Neither is needed to construct a Completer or
set up interactive completion, only to compute completions.

inspect in particular is a heavy import (it pulls in dis, tokenize, ...),
so importing rlcompleter dropped from ~16.4ms to ~1.8ms of cumulative
import time on a local build.  Defer both imports into the methods that use
them and add a lazy-import guard test.

Author: maxday

Lib/rlcompleter.py

@@ -31,9 +31,7 @@
 
 import atexit
 import builtins
-import inspect
 import keyword
-import re
 import __main__
 import warnings
 import types
@@ -105,6 +103,7 @@ def complete(self, text, state):
 
     def _callable_postfix(self, val, word):
         if callable(val):
+            import inspect
             word += "("
             try:
                 if not inspect.signature(val).parameters:
@@ -153,6 +152,7 @@ def attr_matches(self, text):
         with a __getattr__ hook is evaluated.
 
         """
+        import re
         m = re.match(r"(\w+(\.\w+)*)\.(\w*)", text)
         if not m:
             return []

Lib/test/test_rlcompleter.py

@@ -4,6 +4,7 @@
 import types
 import rlcompleter
 from test.support import MISSING_C_DOCSTRINGS
+from test.support.import_helper import ensure_lazy_imports
 
 class CompleteMe:
     """ Trivial class used in testing rlcompleter.Completer. """
@@ -252,5 +253,9 @@ def test_duplicate_globals(self):
         self.assertEqual(completer.complete('Ellipsis', 0), 'Ellipsis()')
         self.assertIsNone(completer.complete('Ellipsis', 1))
 
+    def test_lazy_imports(self):
+        ensure_lazy_imports("rlcompleter", {"inspect", "re"})
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2026-08-25-12-43-10.gh-issue-156363.RlzImp.rst

@@ -0,0 +1,5 @@
+Speed up ``import rlcompleter`` by deferring the imports of :mod:`inspect`
+and :mod:`re` into the completion methods that use them.  They are only
+needed while computing completions, so importing :mod:`rlcompleter` (for
+example when setting up interactive completion) no longer pays their import
+cost.