From 81f6beda9e9131983ae17c05f1d83f733e84896a Mon Sep 17 00:00:00 2001
From: Sebastian Rittau <srittau@rittau.biz>
Date: Wed, 3 May 2023 16:30:37 +0200
Subject: [PATCH] Document sys.std* typing (#10135)

---
 stdlib/sys.pyi | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/stdlib/sys.pyi b/stdlib/sys.pyi
index 786db72c7..c2fdbeccc 100644
--- a/stdlib/sys.pyi
+++ b/stdlib/sys.pyi
@@ -57,9 +57,20 @@ if sys.version_info >= (3, 8):
     pycache_prefix: str | None
 ps1: object
 ps2: object
+
+# TextIO is used instead of more specific types for the standard streams,
+# since they are often monkeypatched at runtime. At startup, the objects
+# are initialized to instances of TextIOWrapper.
+#
+# To use methods from TextIOWrapper, use an isinstance check to ensure that
+# the streams have not been overridden:
+#
+# if isinstance(sys.stdout, io.TextIOWrapper):
+#    sys.stdout.reconfigure(...)
 stdin: TextIO
 stdout: TextIO
 stderr: TextIO
+
 if sys.version_info >= (3, 10):
     stdlib_module_names: frozenset[str]