From a58594429e766dd2532dfb40828e7517194184da Mon Sep 17 00:00:00 2001
From: Yury Selivanov <yury@magic.io>
Date: Wed, 18 Apr 2018 14:20:36 -0400
Subject: [PATCH] pep-567: Add another reason why Contexts are not mutable
 (#623)

---
 pep-0567.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/pep-0567.rst b/pep-0567.rst
index cbc6920d3..3f5f3fffb 100644
--- a/pep-0567.rst
+++ b/pep-0567.rst
@@ -712,6 +712,15 @@ This proposal was deferred to Python 3.8+ because of the following:
 
      ctx.run(func)
 
+3. If ``Context`` was mutable it would mean that context variables
+   could be mutated separately (or concurrently) from the code that
+   runs within the context.  That would be similar to obtaining a
+   reference to a running Python frame object and modifying its
+   ``f_locals`` from another OS thread.  Having one single way to
+   assign values to context variables makes contexts conceptually
+   simpler and more predictable, while keeping the door open for
+   future performance optimizations.
+
 
 Having initial values for ContextVars
 -------------------------------------