Ticket #2265: iterator_choices_try2.patch

django/db/models/fields/__init__.py

@@ -7 +7 @@
 from django.utils.functional import curry
 from django.utils.text import capfirst
 from django.utils.translation import gettext, gettext_lazy
+from django.utils._itertools import tee
 import datetime, os, time
 
 class NOT_PROVIDED:
@@ -80 +81 @@
         self.prepopulate_from = prepopulate_from
         self.unique_for_date, self.unique_for_month = unique_for_date, unique_for_month
         self.unique_for_year = unique_for_year
-        self.choices = choices or []
+        self._choices = choices or []
         self.radio_admin = radio_admin
         self.help_text = help_text
         self.db_column = db_column
@@ -324 +325 @@
     def bind(self, fieldmapping, original, bound_field_class):
         return bound_field_class(self, fieldmapping, original)
 
+    def _get_choices(self):
+        if hasattr(self._choices, 'next'):
+            choices, self._choices = tee(self._choices)
+        else:
+            choices = self._choices
+
+        return choices
+    choices = property(_get_choices)
+
 class AutoField(Field):
     empty_strings_allowed = False
     def __init__(self, *args, **kwargs):

django/utils/_itertools.py

@@ +1 @@
+try:
+    from itertools import tee
+except ImportError:
+    from itertools import count
+
+    def tee(iterable, n=2):
+        """
+        A little bit modified code for n iterators
+        from http://www.python.org/doc/2.3.5/lib/itertools-example.html
+
+        Return n independent iterators from a single iterable
+        """
+        def gen(next, data={}, cnt=[0]):
+            dpop = data.pop
+            for i in count():
+                if i == cnt[0]:
+                    item = data[i] = next()
+                    cnt[0] += 1
+                else:
+                    item = dpop(i)
+                yield item
+        next = iter(iterable).next
+        return (gen(next) for x in xrange(n))