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==========
Pagination
==========
Django provides high-level and low-level ways to help you manage paginated data
-- that is, data that's split across several pages, with "Previous/Next" links.
The ``Paginator`` class
=======================
Under the hood, all methods of pagination use the
:class:`~django.core.paginator.Paginator` class. It does all the heavy lifting
of actually splitting a ``QuerySet`` into parts and handing them over to other
components.
Example
=======
Give :class:`~django.core.paginator.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
>>> type(p.page_range)
<class 'range_iterator'>
>>> p.page_range
range(1, 3)
>>> 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()
Traceback (most recent call last):
...
EmptyPage: That page contains no results
>>> 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):
...
EmptyPage: That page number is less than 1
>>> p.page(3)
Traceback (most recent call last):
...
EmptyPage: That page contains no results
.. note::
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.
Paginating a ``ListView``
=========================
:class:`django.views.generic.list.ListView` provides a builtin way to paginate
the displayed list. You can do this by adding
:attr:`~django.views.generic.list.MultipleObjectMixin.paginate_by` attribute to
your view class, for example::
from django.views.generic import ListView
from myapp.models import Contacts
class ContactsList(ListView):
paginate_by = 2
model = Contacts
The only thing your users will be missing is a way to navigate to the next or
previous page. To achieve this, add links to the next and previous page, like
shown in the below example ``list.html``.
.. _using-paginator-in-view:
Using ``Paginator`` in a view
=============================
Here's a slightly more complex example using
:class:`~django.core.paginator.Paginator` in a view to paginate a queryset. We
give both the view and the accompanying template to show how you can display
the results. This example assumes you have a ``Contacts`` model that has
already been imported.
The view function looks like this::
from django.core.paginator import Paginator
from django.shortcuts import render
def listing(request):
contact_list = Contacts.objects.all()
paginator = Paginator(contact_list, 25) # Show 25 contacts per page
page = request.GET.get('page')
contacts = paginator.get_page(page)
return render(request, 'list.html', {'contacts': contacts})
In the template :file:`list.html`, you'll want to include navigation between
pages along with any interesting information from the objects themselves:
.. code-block:: html+django
{% for contact in contacts %}
{# Each "contact" is a Contact model object. #}
{{ contact.full_name|upper }}<br>
...
{% endfor %}
<div class="pagination">
<span class="step-links">
{% if contacts.has_previous %}
<a href="?page=1">« first</a>
<a href="?page={{ contacts.previous_page_number }}">previous</a>
{% endif %}
<span class="current">
Page {{ contacts.number }} of {{ contacts.paginator.num_pages }}.
</span>
{% if contacts.has_next %}
<a href="?page={{ contacts.next_page_number }}">next</a>
<a href="?page={{ contacts.paginator.num_pages }}">last »</a>
{% endif %}
</span>
</div>
|
