From e4cc3a7c1f5ba9ea2c3015a5bf09cb5b93db5d47 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Thu, 28 May 2020 09:58:33 -0700
Subject: bpo-40806: itertools.product immediately consumes its inputs
 (GH-20492) (GH-20498)

---
 Doc/library/itertools.rst | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 3e5a673..3c94c4b 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -563,6 +563,9 @@ loops that truncate the stream.
            for prod in result:
                yield tuple(prod)
 
+   Before :func:`product` runs, it completely consumes the input iterables,
+   keeping pools of values in memory to generate the products.  Accordingly,
+   it only useful with finite inputs.
 
 .. function:: repeat(object[, times])
 
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