Django 之 Paginator 分页功能

Django Paginator

Django 分页官方文档  https://docs.djangoproject.com/en/1.10/topics/pagination/

 此分页方法没有限制显示出来的页码的个数，会显示全部的页码，待改进。

后端代码

由于代码是先object_list = model_obj.model.objects.all()，然后调用 paginator = Paginator(object_list, 2)，如果数据量很大就会消耗很多的性能。

如果是这样呢写呢？ paginator = Paginator(model_obj.model.objects.all(), 2）  这样能利用queryset的惰性机制吗？ 

看了下Paginator源码，应该是可行的

class Paginator(object):

    def __init__(self, object_list, per_page, orphans=0,
                 allow_empty_first_page=True):
        self.object_list = object_list
        self.per_page = int(per_page)
        self.orphans = int(orphans)
        self.allow_empty_first_page = allow_empty_first_page

    def validate_number(self, number):
        """
        Validates the given 1-based page number.
        """
        try:
            number = int(number)
        except (TypeError, ValueError):
            raise PageNotAnInteger('That page number is not an integer')
        if number < 1:
            raise EmptyPage('That page number is less than 1')
        if number > self.num_pages:
            if number == 1 and self.allow_empty_first_page:
                pass
            else:
                raise EmptyPage('That page contains no results')
        return number

    def page(self, number):
        """
        Returns a Page object for the given 1-based page number.
        """
        number = self.validate_number(number)
        bottom = (number - 1) * self.per_page
        top = bottom + self.per_page
        if top + self.orphans >= self.count:
            top = self.count
        return self._get_page(self.object_list[bottom:top], number, self)

    def _get_page(self, *args, **kwargs):
        """
        Returns an instance of a single page.

        This hook can be used by subclasses to use an alternative to the
        standard :cls:`Page` object.
        """
        return Page(*args, **kwargs)

    @cached_property
    def count(self):
        """
        Returns the total number of objects, across all pages.
        """
        try:
            return self.object_list.count()
        except (AttributeError, TypeError):
            # AttributeError if object_list has no count() method.
            # TypeError if object_list.count() requires arguments
            # (i.e. is of type list).
            return len(self.object_list)

    @cached_property
    def num_pages(self):
        """
        Returns the total number of pages.
        """
        if self.count == 0 and not self.allow_empty_first_page:
            return 0
        hits = max(1, self.count - self.orphans)
        return int(ceil(hits / float(self.per_page)))

    @property
    def page_range(self):
        """
        Returns a 1-based range of pages for iterating through within
        a template for loop.
        """
        return six.moves.range(1, self.num_pages + 1)


QuerySetPaginator = Paginator   # For backwards-compatibility.

#需要导入 的模块
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger 


def display_table_objs(request,app_name,table_name):
    print(app_name,'----',table_name)
    #获取数据库数据
    model_obj = king_admin.enabled_admins[app_name][table_name]

    #分页
    object_list = model_obj.model.objects.all()
    paginator = Paginator(object_list, 2)  # Show 2 contacts per page
    # paginator = JuncheePaginator(object_list, 1)  # Show 2 contacts per page

    page = request.GET.get('page')
    try:
        contacts = paginator.page(page)
    except PageNotAnInteger:
        # If page is not an integer, deliver first page.
        contacts = paginator.page(1)
    except EmptyPage:
        # If page is out of range (e.g. 9999), deliver last page of results.
        contacts = paginator.page(paginator.num_pages)

    return render(request,'king_admin/table_objs.html',{"model_obj":model_obj,
                                                        "query_sets":contacts,})

前端模板代码

其中的标签样式引用的Bootstrap的样式

 <ul class="pagination">
                    {# topics.paginator.page_range 这个函数返回包含一个所有页码数的 range 对象 #}
                    {# 即 range(1, topics.paginator.num_pages + 1) #}
                    {% if query_sets.has_previous %}
                        <li><a href="?page={{ query_sets.previous_page_number }}">上一页</a></li>
                    {% else %}
                        <li><span>没了</span></li>
                    {% endif %}
                    {% for page_number in query_sets.paginator.page_range %}

                        {% ifequal page_number  query_sets.number %}
                            <li class="disabled"><span>{{ page_number }}</span></li>

                        {% else %}
                            <li ><a href="?page={{ page_number }}">{{ page_number }}</a></li>

                        {% endifequal %}
                    {% endfor %}

                    {% if query_sets.has_next %}
                        <li><a href="?page={{ query_sets.next_page_number }}">下一页</a></li>
                    {% else %}
                        <li><span>没了</span></li>
                    {% endif %}
                </ul>

效果如下：