[1.5.x] Fixed #20094 - Be more careful when checking for Iterator

Python 2.6 has some different behaviour when checking
isinstance(foo, collections.Iterator).
Backport of 829dc3c5 from master.

1 files changed, 14 insertions, 1 deletions

diff --git a/django/utils/itercompat.py b/django/utils/itercompat.py
index aa329c152e..2c555bd5ce 100644
--- a/django/utils/itercompat.py
+++ b/django/utils/itercompat.py
@@ -4,10 +4,12 @@ Where possible, we try to use the system-native version and only fall back to
 these implementations if necessary.
 """
 
-from django.utils.six.moves import builtins
+import collections
 import itertools
+import sys
 import warnings
 
+
 def is_iterable(x):
     "A implementation independent way of checking for iterables"
     try:
@@ -17,6 +19,17 @@ def is_iterable(x):
     else:
         return True
 
+def is_iterator(x):
+    """An implementation independent way of checking for iterators
+
+    Python 2.6 has a different implementation of collections.Iterator which
+    accepts anything with a `next` method. 2.7+ requires and `__iter__` method
+    as well.
+    """
+    if sys.version_info >= (2, 7):
+        return isinstance(x, collections.Iterator)
+    return isinstance(x, collections.Iterator) and hasattr(x, '__iter__')
+
 def product(*args, **kwds):
     warnings.warn("django.utils.itercompat.product is deprecated; use the native version instead",
                   PendingDeprecationWarning)