From 2e3e764f80e1f1da2354ac38891efe0988e3be48 Mon Sep 17 00:00:00 2001
From: stijn <stijn@ignitron.net>
Date: Tue, 25 Aug 2015 14:36:45 +0200
Subject: [PATCH] itertools: Make cycle() work with finite generators

---
 itertools/itertools.py | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/itertools/itertools.py b/itertools/itertools.py
index ea6f40e4..8d12ce90 100644
--- a/itertools/itertools.py
+++ b/itertools/itertools.py
@@ -4,8 +4,19 @@ def count(start=0, step=1):
         start += step
 
 def cycle(p):
-    while p:
-        yield from p
+    try:
+        len(p)
+        while p:
+            yield from p
+    except TypeError:
+        # len() is not defined for this type. Assume it is
+        # a finite iterable so we must cache the elements.
+        cache = []
+        for i in p:
+            yield i
+            cache.append(i)
+        while cache:
+            yield from cache
 
 def repeat(el, n=None):
     if n is None: