From cfc6ce4d40f2f01314b7e283fb972a7bb3ed3faa Mon Sep 17 00:00:00 2001
From: Ramil Nugmanov <nougmanoff@protonmail.com>
Date: Thu, 28 May 2020 19:46:22 +0300
Subject: [PATCH] bpo-40806: Clarify that itertools.product immediately
 consumes its inpt (GH-20492)

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

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 3e5a6738981..3c94c4b35dc 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])