Made the Paginator class a bit more backwards compatible with the lecacy…

Made the Paginator class a bit more backwards compatible with the lecacy `ObjectPaginator` class by using the `ObjectPaginator`'s `_get_count` method.  Instead of explicitly checking for an instance of `QuerySet`, this now allows any object with a `count()` or `__len__()` method defined to be passed to Paginator.  For one, this is useful when you have custom `QuerySet`-like classes that implement a `count()` method but don't inherit from `QuerySet` explicitly.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@8121 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/paginator.py

@@ -42,10 +42,12 @@ class Paginator(object):
     def _get_count(self):
         "Returns the total number of objects, across all pages."
         if self._count is None:
-            from django.db.models.query import QuerySet
-            if isinstance(self.object_list, QuerySet):
+            try:
                 self._count = self.object_list.count()
-            else:
+            except (AttributeError, TypeError):
+                # AttributeError if object_list has no count() method.
+                # TypeError if object_list.count() requires arguments
+                # (i.e. is of type list).
                 self._count = len(self.object_list)
         return self._count
     count = property(_get_count)
@@ -169,22 +171,8 @@ class ObjectPaginator(Paginator):
             return self.count
         return page_number * self.num_per_page
 
-    def _get_count(self):
-        # The old API allowed for self.object_list to be either a QuerySet or a
-        # list. Here, we handle both.
-        if self._count is None:
-            try:
-                self._count = self.object_list.count()
-            except (AttributeError, TypeError):
-                # AttributeError if object_list has no count() method.
-                # TypeError if object_list.count() requires arguments
-                # (i.e. is of type list).
-                self._count = len(self.object_list)
-        return self._count
-    count = property(_get_count)
-
     # The old API called it "hits" instead of "count".
-    hits = count
+    hits = Paginator.count
 
     # The old API called it "pages" instead of "num_pages".
     pages = Paginator.num_pages

docs/pagination.txt

@@ -59,10 +59,12 @@ page::
     ...
     InvalidPage
 
-Note that you can give ``Paginator`` a list/tuple or a Django ``QuerySet``. The
-only difference is in implementation; if you pass a ``QuerySet``, the
-``Paginator`` will call its ``count()`` method instead of using ``len()``,
-because the former is more efficient.
+Note that you can give ``Paginator`` a list/tuple, a Django ``QuerySet``, or
+any other object with a ``count()`` or ``__len__()`` method. When determining
+the number of objects contained in the passed object, ``Paginator`` will first
+try calling ``count()``, then fallback to using ``len()`` if the passed object
+has no ``count()`` method. This allows objects such as Django's ``QuerySet`` to
+use a more efficient ``count()`` method when available.
 
 ``Paginator`` objects
 =====================

tests/modeltests/pagination/models.py

@@ -140,6 +140,31 @@ True
 >>> p.end_index()
 5
 
+# Paginator can be passed other objects with a count() method.
+>>> class CountContainer:
+...     def count(self):
+...         return 42
+>>> paginator = Paginator(CountContainer(), 10)
+>>> paginator.count
+42
+>>> paginator.num_pages
+5
+>>> paginator.page_range
+[1, 2, 3, 4, 5]
+
+# Paginator can be passed other objects that implement __len__.
+>>> class LenContainer:
+...     def __len__(self):
+...         return 42
+>>> paginator = Paginator(LenContainer(), 10)
+>>> paginator.count
+42
+>>> paginator.num_pages
+5
+>>> paginator.page_range
+[1, 2, 3, 4, 5]
+
+
 ################################
 # Legacy API (ObjectPaginator) #
 ################################