From 5cd184fa32e29bc9c690ce15346b9fccea5f5df2 Mon Sep 17 00:00:00 2001
From: correctmost <134317971+correctmost@users.noreply.github.com>
Date: Fri, 10 May 2024 15:46:58 -0400
Subject: [PATCH] Improve performance of _get_zipimporters

_get_zipimporters can call isinstance millions of times when
running pylint's import-error checker on a codebase like yt-dlp.

Checking for None first avoids the overhead of invoking isinstance.

Closes pylint-dev/pylint#9607.
---
 astroid/interpreter/_import/spec.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/astroid/interpreter/_import/spec.py b/astroid/interpreter/_import/spec.py
index 469508da83..59546a016a 100644
--- a/astroid/interpreter/_import/spec.py
+++ b/astroid/interpreter/_import/spec.py
@@ -341,7 +341,7 @@ def _is_setuptools_namespace(location: pathlib.Path) -> bool:
 
 def _get_zipimporters() -> Iterator[tuple[str, zipimport.zipimporter]]:
     for filepath, importer in sys.path_importer_cache.items():
-        if isinstance(importer, zipimport.zipimporter):
+        if importer is not None and isinstance(importer, zipimport.zipimporter):
             yield filepath, importer