153 lines
4.7 KiB
Plaintext
153 lines
4.7 KiB
Plaintext
==========
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Pagination
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==========
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Django provides high-level and low-level ways to help you manage paginated data
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-- that is, data that's split across several pages, with "Previous/Next" links.
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The ``Paginator`` class
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=======================
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Under the hood, all methods of pagination use the
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:class:`~django.core.paginator.Paginator` class. It does all the heavy lifting
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of actually splitting a ``QuerySet`` into parts and handing them over to other
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components.
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Example
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=======
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Give :class:`~django.core.paginator.Paginator` a list of objects, plus the
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number of items you'd like to have on each page, and it gives you methods for
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accessing the items for each page::
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>>> from django.core.paginator import Paginator
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>>> objects = ['john', 'paul', 'george', 'ringo']
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>>> p = Paginator(objects, 2)
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>>> p.count
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4
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>>> p.num_pages
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2
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>>> type(p.page_range)
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<class 'range_iterator'>
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>>> p.page_range
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range(1, 3)
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>>> page1 = p.page(1)
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>>> page1
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<Page 1 of 2>
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>>> page1.object_list
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['john', 'paul']
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>>> page2 = p.page(2)
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>>> page2.object_list
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['george', 'ringo']
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>>> page2.has_next()
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False
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>>> page2.has_previous()
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True
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>>> page2.has_other_pages()
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True
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>>> page2.next_page_number()
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Traceback (most recent call last):
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...
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EmptyPage: That page contains no results
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>>> page2.previous_page_number()
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1
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>>> page2.start_index() # The 1-based index of the first item on this page
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3
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>>> page2.end_index() # The 1-based index of the last item on this page
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4
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>>> p.page(0)
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Traceback (most recent call last):
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...
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EmptyPage: That page number is less than 1
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>>> p.page(3)
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Traceback (most recent call last):
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...
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EmptyPage: That page contains no results
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.. note::
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Note that you can give ``Paginator`` a list/tuple, a Django ``QuerySet``,
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or any other object with a ``count()`` or ``__len__()`` method. When
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determining the number of objects contained in the passed object,
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``Paginator`` will first try calling ``count()``, then fallback to using
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``len()`` if the passed object has no ``count()`` method. This allows
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objects such as Django's ``QuerySet`` to use a more efficient ``count()``
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method when available.
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Paginating a ``ListView``
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=========================
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:class:`django.views.generic.list.ListView` provides a builtin way to paginate
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the displayed list. You can do this by adding
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:attr:`~django.views.generic.list.MultipleObjectMixin.paginate_by` attribute to
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your view class, for example::
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from django.views.generic import ListView
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from myapp.models import Contacts
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class ContactsList(ListView):
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paginate_by = 2
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model = Contacts
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The only thing your users will be missing is a way to navigate to the next or
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previous page. To achieve this, add links to the next and previous page, like
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shown in the below example ``list.html``.
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.. _using-paginator-in-view:
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Using ``Paginator`` in a view
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=============================
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Here's a slightly more complex example using
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:class:`~django.core.paginator.Paginator` in a view to paginate a queryset. We
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give both the view and the accompanying template to show how you can display
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the results. This example assumes you have a ``Contacts`` model that has
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already been imported.
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The view function looks like this::
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from django.core.paginator import Paginator
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from django.shortcuts import render
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def listing(request):
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contact_list = Contacts.objects.all()
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paginator = Paginator(contact_list, 25) # Show 25 contacts per page
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page = request.GET.get('page')
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contacts = paginator.get_page(page)
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return render(request, 'list.html', {'contacts': contacts})
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In the template :file:`list.html`, you'll want to include navigation between
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pages along with any interesting information from the objects themselves:
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.. code-block:: html+django
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{% for contact in contacts %}
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{# Each "contact" is a Contact model object. #}
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{{ contact.full_name|upper }}<br>
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...
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{% endfor %}
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<div class="pagination">
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<span class="step-links">
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{% if contacts.has_previous %}
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<a href="?page=1">« first</a>
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<a href="?page={{ contacts.previous_page_number }}">previous</a>
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{% endif %}
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<span class="current">
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Page {{ contacts.number }} of {{ contacts.paginator.num_pages }}.
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</span>
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{% if contacts.has_next %}
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<a href="?page={{ contacts.next_page_number }}">next</a>
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<a href="?page={{ contacts.paginator.num_pages }}">last »</a>
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{% endif %}
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</span>
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</div>
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