From c7074007272f257a0efab76f03e6b400c30a51b4 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Sun, 25 Nov 2018 17:00:37 -0800
Subject: bpo-35300: Add usage note to the lru_cache() docs (GH-10707)
 (GH-10708)

---
 Doc/library/functools.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index 8924593..d19373b 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -85,6 +85,11 @@ The :mod:`functools` module defines the following functions:
    The cache's size limit assures that the cache does not grow without bound on
    long-running processes such as web servers.
 
+   In general, the LRU cache should only be used when you want to reuse
+   previously computed values.  Accordingly, it doesn't make sense to cache
+   functions with side-effects, functions that need to create distinct mutable
+   objects on each call, or impure functions such as time() or random().
+
    Example of an LRU cache for static web content::
 
         @lru_cache(maxsize=32)
-- 
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