django/docs/pagination.txt

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==========
Pagination
==========
**New in Django development version**
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 the module ``django/core/paginator.py``.
Example
=======
Give ``Paginator`` a list of objects, plus the number of items you'd like to
have on each page, and it gives you methods for accessing the items for each
page::
>>> from django.core.paginator import Paginator
>>> objects = ['john', 'paul', 'george', 'ringo']
>>> p = Paginator(objects, 2)
>>> p.count
4
>>> p.num_pages
2
>>> p.page_range
[1, 2]
>>> page1 = p.page(1)
>>> page1
<Page 1 of 2>
>>> page1.object_list
['john', 'paul']
>>> page2 = p.page(2)
>>> page2.object_list
['george', 'ringo']
>>> page2.has_next()
False
>>> page2.has_previous()
True
>>> page2.has_other_pages()
True
>>> page2.next_page_number()
3
>>> page2.previous_page_number()
1
>>> page2.start_index() # The 1-based index of the first item on this page
3
>>> page2.end_index() # The 1-based index of the last item on this page
4
>>> p.page(0)
Traceback (most recent call last):
...
InvalidPage
>>> p.page(3)
Traceback (most recent call last):
...
InvalidPage
``Paginator`` objects
=====================
Required arguments
------------------
``object_list``
A list, tuple, Django ``QuerySet``, or other sliceable object with a
``count()`` or ``__len__()`` method.
``per_page``
The maximum number of items to include on a page, not including orphans
(see the ``orphans`` optional argument below).
Optional arguments
------------------
``orphans``
The minimum number of items allowed on the last page, defaults to zero.
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.
``allow_empty_first_page``
Whether or not the first page is allowed to be empty. If ``False`` and
``object_list`` is empty, then a ``EmptyPage`` error will be raised.
Methods
-------
``page(number)``
Returns a ``Page`` object with the given 1-based index. Raises
``InvalidPage`` if the given page number doesn't exist.
Attributes
----------
In addition to the arguments above, which get stored as attributes, a
``Paginator`` object also has the following attributes:
``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 fallback to using ``object_list.__len__()``. This allows
objects, such as Django's ``QuerySet``, to use a more efficient ``count()``
method when available.
``num_pages``
The total number of pages.
``page_range``
A 1-based range of page numbers, e.g., ``[1, 2, 3, 4]``.
``InvalidPage`` exceptions
==========================
The ``page()`` method raises ``InvalidPage`` if the requested page is invalid
(i.e., not an integer) or contains no objects. Generally, it's enough to trap
the ``InvalidPage`` exception, but if you'd like more granularity, you can trap
either of the following exceptions:
``PageNotAnInteger``
Raised when ``page()`` is given a value that isn't an integer.
``EmptyPage``
Raised when ``page()`` is given a valid value but no objects exist on that
page.
Both of the exceptions are subclasses of ``InvalidPage``, so you can handle
them both with a simple ``except InvalidPage``.
``Page`` objects
================
Methods
-------
``has_next()``
Returns ``True`` if there's a next page.
``has_previous()``
Returns ``True`` if there's a previous page.
``has_other_pages()``
Returns ``True`` if there's a next *or* previous page.
``next_page_number()``
Returns the next page number. Note that this is "dumb" and will return the
next page number regardless of whether a subsequent page exists.
``previous_page_number()``
Returns the previous page number. Note that this is "dumb" and will return
the previous page number regardless of whether a previous page exists.
``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 ``start_index()``
would return ``3``.
``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 ``end_index()``
would return ``4``.
Attributes
----------
``object_list``
The list of objects on this page.
``number``
The 1-based page number for this page.
``paginator``
The associated ``Paginator`` object.