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 django/core/paginator.py.
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
>>> 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
注解
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.
PaginatorPHere's a slightly more complex example using 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 list.html, you'll want to include navigation between
pages along with any interesting information from the objects themselves:
{% 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>
Paginator 对象PPaginator 类的构造方法是:
object_listA list, tuple, QuerySet, or other sliceable object with a count()
or __len__() method. For consistent pagination, QuerySets should
be ordered, e.g. with an order_by()
clause or with a default ordering on the
model.
Performance issues paginating large QuerySets
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.
per_pageorphans optional argument below).orphansorphans, 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.allow_empty_first_pageFalse and
object_list is empty, then an EmptyPage error will be raised.Paginator.get_page(number)[源代码]PReturns a 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.
It raises an exception (EmptyPage) only if you specify
Paginator(..., allow_empty_first_page=False) and the object_list is
empty.
Paginator.page(number)[源代码]PReturns a Page object with the given 1-based index. Raises
InvalidPage if the given page number doesn't exist.
Paginator.countPThe total number of objects, across all pages.
注解
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 len(object_list). This allows objects, such as
Django's QuerySet, to use a more efficient count() method when
available.
Paginator.num_pagesPThe total number of pages.
Paginator.page_rangePA 1-based range iterator of page numbers, e.g. yielding [1, 2, 3, 4].
InvalidPage exceptionsPThe 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:
EmptyPage[源代码]PRaised 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 objectsP你通常不会手动实例化Page对象 - 你会使用方法Paginator.page()。
Page(object_list, number, paginator)[源代码]PA page acts like a sequence of Page.object_list when using
len() or iterating it directly.
Page.next_page_number()[源代码]PReturns the next page number. Raises InvalidPage if next page
doesn't exist.
Page.previous_page_number()[源代码]PReturns the previous page number. Raises InvalidPage if previous
page doesn't exist.
Page.start_index()[源代码]PReturns 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.
Page.end_index()[源代码]PReturns 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.
8月 23, 2019