Pagination

Django provides a few classes that help you manage paginated data — that is,data that's split across several pages, with "Previous/Next" links. Theseclasses live in django/core/paginator.py.

例如

Give Paginator a list of objects, plus the number of items you'd like tohave on each page, and it gives you methods for accessing the items for eachpage:

  1. >>> from django.core.paginator import Paginator
  2. >>> objects = ['john', 'paul', 'george', 'ringo']
  3. >>> p = Paginator(objects, 2)
  4.  
  5. >>> p.count
  6. 4
  7. >>> p.num_pages
  8. 2
  9. >>> type(p.page_range)
  10. <class 'range_iterator'>
  11. >>> p.page_range
  12. range(1, 3)
  13.  
  14. >>> page1 = p.page(1)
  15. >>> page1
  16. <Page 1 of 2>
  17. >>> page1.object_list
  18. ['john', 'paul']
  19.  
  20. >>> page2 = p.page(2)
  21. >>> page2.object_list
  22. ['george', 'ringo']
  23. >>> page2.has_next()
  24. False
  25. >>> page2.has_previous()
  26. True
  27. >>> page2.has_other_pages()
  28. True
  29. >>> page2.next_page_number()
  30. Traceback (most recent call last):
  31. ...
  32. EmptyPage: That page contains no results
  33. >>> page2.previous_page_number()
  34. 1
  35. >>> page2.start_index() # The 1-based index of the first item on this page
  36. 3
  37. >>> page2.end_index() # The 1-based index of the last item on this page
  38. 4
  39.  
  40. >>> p.page(0)
  41. Traceback (most recent call last):
  42. ...
  43. EmptyPage: That page number is less than 1
  44. >>> p.page(3)
  45. Traceback (most recent call last):
  46. ...
  47. 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. Whendetermining the number of objects contained in the passed object,Paginator will first try calling count(), then fallback to usinglen() if the passed object has no count() method. This allowsobjects such as Django's QuerySet to use a more efficient count()method when available.

Using Paginator in a view

Here's a slightly more complex example using Paginator in a view topaginate a queryset. We give both the view and the accompanying template toshow how you can display the results. This example assumes you have aContacts model that has already been imported.

The view function looks like this:

  1. from django.core.paginator import EmptyPage, PageNotAnInteger, Paginator
  2. from django.shortcuts import render
  3.  
  4. def listing(request):
  5.     contact_list = Contacts.objects.all()
  6.     paginator = Paginator(contact_list, 25) # Show 25 contacts per page
  7.  
  8.     page = request.GET.get('page')
  9.     contacts = paginator.get_page(page)
  10.     return render(request, 'list.html', {'contacts': contacts})

In the template list.html, you'll want to include navigation betweenpages along with any interesting information from the objects themselves:

  1. {% for contact in contacts %}
  2.     {# Each "contact" is a Contact model object. #}
  3.     {{ contact.full_name|upper }}<br />
  4.     ...
  5. {% endfor %}
  6.  
  7. <div class="pagination">
  8.     <span class="step-links">
  9.         {% if contacts.has_previous %}
  10.             <a href="?page=1">&laquo; first</a>
  11.             <a href="?page={{ contacts.previous_page_number }}">previous</a>
  12.         {% endif %}
  13.  
  14.         <span class="current">
  15.             Page {{ contacts.number }} of {{ contacts.paginator.num_pages }}.
  16.         </span>
  17.  
  18.         {% if contacts.has_next %}
  19.             <a href="?page={{ contacts.next_page_number }}">next</a>
  20.             <a href="?page={{ contacts.paginator.num_pages }}">last &raquo;</a>
  21.         {% endif %}
  22.     </span>
  23. </div>

Paginator objects

The Paginator class has this constructor:

  • class Paginator(object_list, per_page, orphans=0, allow_empty_first_page=True)[source]

必选参数

  • object_list
  • A list, tuple, QuerySet, or other sliceable object with a count()or len() method. For consistent pagination, QuerySets shouldbe ordered, e.g. with an order_by()clause or with a default ordering on themodel.

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, becausethe resulting LIMIT/OFFSET query needs to count the number ofOFFSET records which takes longer as the page number gets higher.

  • per_page
  • The maximum number of items to include on a page, not including orphans(see the orphans optional argument below).

可选参数

  • orphans
  • 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 equalto orphans, then those items will be added to the previous page (whichbecomes the last page) instead of leaving the items on a page bythemselves. For example, with 23 items, per_page=10, andorphans=3, there will be two pages; the first page with 10 items andthe 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_page
  • Whether or not the first page is allowed to be empty. If False andobject_list is empty, then an EmptyPage error will be raised.

方法

  • Paginator.getpage(_number)[source]
  • New in Django 2.0.

Returns a Page object with the given 1-based index, while alsohandling out of range and invalid page numbers.

If the page isn't a number, it returns the first page. If the page numberis negative or greater than the number of pages, it returns the last page.

It raises an exception (EmptyPage) only if you specifyPaginator(…, allow_empty_first_page=False) and the object_list isempty.

  • Paginator.page(number)[source]
  • Returns a Page object with the given 1-based index. RaisesInvalidPage if the given page number doesn't exist.

属性

  • 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(). Ifobject_list has no count() method, then Paginator willfallback to using len(object_list). This allows objects, such asDjango's QuerySet, to use a more efficient count() method whenavailable.

  • Paginator.num_pages

  • The total number of pages.

  • Paginator.page_range

  • A 1-based range iterator of page numbers, e.g. yielding [1, 2, 3, 4].

InvalidPage exceptions

  • exception InvalidPage[source]
  • A base class for exceptions raised when a paginator is passed an invalidpage number.

The Paginator.page() method raises an exception if the requested page isinvalid (i.e., not an integer) or contains no objects. Generally, it's enoughto catch the InvalidPage exception, but if you'd like more granularity,you can catch either of the following exceptions:

  • exception PageNotAnInteger[source]

  • Raised when page() is given a value that isn't an integer.

  • exception EmptyPage[source]

  • Raised when page() is given a valid value but no objects exist on thatpage.

Both of the exceptions are subclasses of InvalidPage, so you can handlethem both with a simple except InvalidPage.

Page objects

You usually won't construct Page objects by hand — you'll get themusing Paginator.page().

  • class Page(object_list, number, paginator)[source]
  • A page acts like a sequence of Page.object_list when usinglen() or iterating it directly.

方法

  • Page.has_next()[source]

  • Returns True if there's a next page.

  • Page.has_previous()[source]

  • Returns True if there's a previous page.

  • Page.has_other_pages()[source]

  • Returns True if there's a next or previous page.

  • Page.next_page_number()[source]

  • Returns the next page number. Raises InvalidPage if next pagedoesn't exist.

  • Page.previous_page_number()[source]

  • Returns the previous page number. Raises InvalidPage if previouspage doesn't exist.

  • Page.start_index()[source]

  • Returns the 1-based index of the first object on the page, relative to allof the objects in the paginator's list. For example, when paginating a listof 5 objects with 2 objects per page, the second page'sstart_index() would return 3.

  • Page.end_index()[source]

  • Returns the 1-based index of the last object on the page, relative to allof the objects in the paginator's list. For example, when paginating a listof 5 objects with 2 objects per page, the second page'send_index() would return 4.

属性

  • Page.object_list

  • 此页上的对象列表。

  • Page.number

  • 此页的基于 1 的页码。

  • Page.paginator

  • 关联的 Paginator 对象。