django/docs/ref/paginator.txt

=========
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`.

For examples, see the :doc:`Pagination topic guide </topics/pagination>`.

.. 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, error_messages=None)

    A paginator acts like a sequence of :class:`Page` when using ``len()`` or
    iterating it directly.

.. 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.

.. attribute:: Paginator.error_messages

    The ``error_messages`` argument lets you override the default messages that
    the paginator will raise. Pass in a dictionary with keys matching the error
    messages you want to override. Available error message keys are:
    ``invalid_page``, ``min_page``, and ``no_results``.

    For example, here is the default error message:

    .. code-block:: pycon

        >>> from django.core.paginator import Paginator
        >>> paginator = Paginator([1, 2, 3], 2)
        >>> paginator.page(5)
        Traceback (most recent call last):
          ...
        EmptyPage: That page contains no results

    And here is a custom error message:

    .. code-block:: pycon

        >>> paginator = Paginator(
        ...     [1, 2, 3],
        ...     2,
        ...     error_messages={"no_results": "Page does not exist"},
        ... )
        >>> paginator.page(5)
        Traceback (most recent call last):
          ...
        EmptyPage: Page does not exist

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:`PageNotAnInteger` if the ``number`` cannot be converted to an integer
    by calling ``int()``. Raises :exc:`EmptyPage` if the given page number
    doesn't exist.

.. method:: Paginator.get_elided_page_range(number, *, on_each_side=3, on_ends=2)

    Returns a 1-based list of page numbers similar to
    :attr:`Paginator.page_range`, but may add an ellipsis to either or both
    sides of the current page number when :attr:`Paginator.num_pages` is large.

    The number of pages to include on each side of the current page number is
    determined by the ``on_each_side`` argument which defaults to 3.

    The number of pages to include at the beginning and end of page range is
    determined by the ``on_ends`` argument which defaults to 2.

    For example, with the default values for ``on_each_side`` and ``on_ends``,
    if the current page is 10 and there are 50 pages, the page range will be
    ``[1, 2, '…', 7, 8, 9, 10, 11, 12, 13, '…', 49, 50]``. This will result in
    pages 7, 8, and 9 to the left of and 11, 12, and 13 to the right of the
    current page as well as pages 1 and 2 at the start and 49 and 50 at the
    end.

    Raises :exc:`InvalidPage` if the given page number doesn't exist.

Attributes
----------

.. attribute:: Paginator.ELLIPSIS

    A translatable string used as a substitute for elided page numbers in the
    page range returned by :meth:`~Paginator.get_elided_page_range`. Default is
    ``'…'``.

.. 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 by
iterating :class:`Paginator`, or by 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``.