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=========
Paginator
=========
Django provides a few classes that help you manage paginated data -- that is,
data that's split across several pages, with "Previous/Next" links. These
classes live in :source:`django/core/paginator.py`.
.. module:: django.core.paginator
:synopsis: Classes to help you easily manage paginated data.
``Paginator`` class
===================
.. class:: Paginator(object_list, per_page, orphans=0, allow_empty_first_page=True)
.. attribute:: Paginator.object_list
Required. A list, tuple, ``QuerySet``, or other sliceable object with a
``count()`` or ``__len__()`` method. For consistent pagination,
``QuerySet``\s should be ordered, e.g. with an
:meth:`~django.db.models.query.QuerySet.order_by` clause or with a default
:attr:`~django.db.models.Options.ordering` on the model.
.. admonition:: Performance issues paginating large ``QuerySet``\s
If you're using a ``QuerySet`` with a very large number of items,
requesting high page numbers might be slow on some databases, because
the resulting ``LIMIT``/``OFFSET`` query needs to count the number of
``OFFSET`` records which takes longer as the page number gets higher.
.. attribute:: Paginator.per_page
Required. The maximum number of items to include on a page, not including
orphans (see the :attr:`~Paginator.orphans` optional argument below).
.. attribute:: Paginator.orphans
Optional. Use this when you don't want to have a last page with very few
items. If the last page would normally have a number of items less than or
equal to ``orphans``, then those items will be added to the previous page
(which becomes the last page) instead of leaving the items on a page by
themselves. For example, with 23 items, ``per_page=10``, and ``orphans=3``,
there will be two pages; the first page with 10 items and the second
(and last) page with 13 items. ``orphans`` defaults to zero, which means
pages are never combined and the last page may have one item.
.. attribute:: Paginator.allow_empty_first_page
Optional. Whether or not the first page is allowed to be empty. If
``False`` and ``object_list`` is empty, then an ``EmptyPage`` error will
be raised.
Methods
-------
.. method:: Paginator.get_page(number)
Returns a :class:`Page` object with the given 1-based index, while also
handling out of range and invalid page numbers.
If the page isn't a number, it returns the first page. If the page number
is negative or greater than the number of pages, it returns the last page.
Raises an :exc:`EmptyPage` exception only if you specify
``Paginator(..., allow_empty_first_page=False)`` and the ``object_list`` is
empty.
.. method:: Paginator.page(number)
Returns a :class:`Page` object with the given 1-based index. Raises
:exc:`InvalidPage` if the given page number doesn't exist.
Attributes
----------
.. attribute:: Paginator.count
The total number of objects, across all pages.
.. note::
When determining the number of objects contained in ``object_list``,
``Paginator`` will first try calling ``object_list.count()``. If
``object_list`` has no ``count()`` method, then ``Paginator`` will
fall back to using ``len(object_list)``. This allows objects, such as
``QuerySet``, to use a more efficient ``count()`` method when
available.
.. attribute:: Paginator.num_pages
The total number of pages.
.. attribute:: Paginator.page_range
A 1-based range iterator of page numbers, e.g. yielding ``[1, 2, 3, 4]``.
``Page`` class
==============
You usually won't construct ``Page`` objects by hand -- you'll get them using
:meth:`Paginator.page`.
.. class:: Page(object_list, number, paginator)
A page acts like a sequence of :attr:`Page.object_list` when using
``len()`` or iterating it directly.
Methods
-------
.. method:: Page.has_next()
Returns ``True`` if there's a next page.
.. method:: Page.has_previous()
Returns ``True`` if there's a previous page.
.. method:: Page.has_other_pages()
Returns ``True`` if there's a next **or** previous page.
.. method:: Page.next_page_number()
Returns the next page number. Raises :exc:`InvalidPage` if next page
doesn't exist.
.. method:: Page.previous_page_number()
Returns the previous page number. Raises :exc:`InvalidPage` if previous
page doesn't exist.
.. method:: Page.start_index()
Returns the 1-based index of the first object on the page, relative to all
of the objects in the paginator's list. For example, when paginating a list
of 5 objects with 2 objects per page, the second page's
:meth:`~Page.start_index` would return ``3``.
.. method:: Page.end_index()
Returns the 1-based index of the last object on the page, relative to all
of the objects in the paginator's list. For example, when paginating a list
of 5 objects with 2 objects per page, the second page's
:meth:`~Page.end_index` would return ``4``.
Attributes
----------
.. attribute:: Page.object_list
The list of objects on this page.
.. attribute:: Page.number
The 1-based page number for this page.
.. attribute:: Page.paginator
The associated :class:`Paginator` object.
Exceptions
==========
.. exception:: InvalidPage
A base class for exceptions raised when a paginator is passed an invalid
page number.
The :meth:`Paginator.page` method raises an exception if the requested page is
invalid (i.e. not an integer) or contains no objects. Generally, it's enough
to catch the ``InvalidPage`` exception, but if you'd like more granularity,
you can catch either of the following exceptions:
.. exception:: PageNotAnInteger
Raised when :meth:`~Paginator.page` is given a value that isn't an integer.
.. exception:: EmptyPage
Raised when :meth:`~Paginator.page` is given a valid value but no objects
exist on that page.
Both of the exceptions are subclasses of :exc:`InvalidPage`, so you can handle
them both with ``except InvalidPage``.
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