Add caching to guarded_import to boost performance

CHANGES.rst

@@ -7,6 +7,8 @@ For changes before version 3.0, see ``HISTORY.rst``.
 7.4 (unreleased)
 ----------------
 
+- Add caching for ``guarded_import`` in Python Scripts. This can speed up the
+  execution of Scripts considerably if they use many ``import`` statements.
 
 7.3 (2025-11-16)
 ----------------

src/AccessControl/ZopeGuards.py

@@ -416,6 +416,12 @@ def guarded_zip(*seqs):
 
 import_default_level = 0
 
+# Cache of (mname, fromlist) pairs whose security check has already passed.
+# Module security in Zope is configured globally, so the result is the same
+# for every request/user — skipping the repeated validate() calls saves
+# significant CPU on instances where Scripts run many imports per request.
+_guarded_import_cache = set()
+
 
 def guarded_import(mname, globals=None, locals=None, fromlist=None,
                    level=import_default_level):
@@ -430,6 +436,10 @@ def guarded_import(mname, globals=None, locals=None, fromlist=None,
         raise Unauthorized("Using import with a level specification isn't "
                            "supported by AccessControl: %s" % mname)
 
+    cache_key = (mname, tuple(fromlist))
+    if cache_key in _guarded_import_cache:
+        return __import__(mname, globals, locals, fromlist)
+
     mnameparts = mname.split('.')
     validate = getSecurityManager().validate
     module = load_module(None, None, mnameparts, validate, globals, locals)
@@ -443,6 +453,7 @@ def guarded_import(mname, globals=None, locals=None, fromlist=None,
         if not validate(module, module, name, v):
             raise Unauthorized
     else:
+        _guarded_import_cache.add(cache_key)
         return __import__(mname, globals, locals, fromlist)