分页
当数据库中数据有很多，我们通常会在前端页面做分页展示。
分页的数据可以在前端页面实现，也可以在后端实现分页。
后端实现分页的原理就是每次只请求一页数据。
准备工作
我们使用脚本批量创建一些测试数据（将下面的代码保存到bulk_create.py文件中放到Django项目的根目录，直接执行即可。）：
import os import sys if __name__ == "__main__": os.environ.setdefault("DJANGO_SETTINGS_MODULE", "day71.settings") import django django.setup() from app01 import models # obj = [models.Book(price= i,title='沙河{}'.format(i)) for i in range(1000)] # # models.Book.objects.bulk_create(obj,100) obj = [models.Author(age= i, name='猪八戒{}'.format(i)) for i in range(500)] models.Author.objects.bulk_create(obj,100)
自定义分页
def publisher_list(request): # 从URL中取当前访问的页码数 try: current_page = int(request.GET.get('page')) except Exception as e: # 取不到或者页码数不是数字都默认展示第1页 current_page = 1 # 总数据量 total_count = models.Publisher.objects.count() # 定义每页显示多少条数据 per_page = 10 # 计算出总页码数 total_page, more = divmod(total_count, per_page) if more: total_page += 1 # 定义页面上最多显示多少页码(为了左右对称，一般设为奇数) max_show = 11 half_show = max_show // 2 # 计算一下页面显示的页码范围 if total_page <= max_show: # 总页码数小于最大显示页码数 page_start = 1 page_end = total_page elif current_page + half_show >= total_page: # 右边越界 page_end = total_page page_start = total_page - max_show elif current_page - half_show <= 1: # 左边越界 page_start = 1 page_end = max_show else: # 正常页码区间 page_start = current_page - half_show page_end = current_page + half_show # 数据索引起始位置 data_start = (current_page-1) * per_page data_end = current_page * per_page publisher_list = models.Publisher.objects.all()[data_start:data_end] # 生成页面上显示的页码 page_html_list = [] page_html_list.append('<nav aria-label="Page navigation"><ul class="pagination">') # 加首页 first_li = '<li><a href="/publisher_list/?page=1">首页</a></li>' page_html_list.append(first_li) # 加上一页 if current_page == 1: prev_li = '<li><a href="#"><span aria-hidden="true">«</span></a></li>' else: prev_li = '<li><a href="/publisher_list/?page={}"><span aria-hidden="true">«</span></a></li>'.format(current_page - 1) page_html_list.append(prev_li) for i in range(page_start, page_end + 1): if i == current_page: li_tag = '<li class="active"><a href="/publisher_list/?page={0}">{0}</a></li>'.format(i) else: li_tag = '<li><a href="/publisher_list/?page={0}">{0}</a></li>'.format(i) page_html_list.append(li_tag) # 加下一页 if current_page == total_page: next_li = '<li><a href="#"><span aria-hidden="true">»</span></a></li>' else: next_li = '<li><a href="/publisher_list/?page={}"><span aria-hidden="true">»</span></a></li>'.format(current_page + 1) page_html_list.append(next_li) # 加尾页 page_end_li = '<li><a href="/publisher_list/?page={}">尾页</a></li>'.format(total_page) page_html_list.append(page_end_li) page_html_list.append('</ul></nav>') page_html = "".join(page_html_list) return render(request, "publisher_list.html", {"publisher_list": publisher_list, "page_html": page_html})
class Page(): """自定义分页（Bootstrap版）""" def __init__(self, page_num, total_count, url_prefix, per_page=10, max_page=11): """ :param page_num: 用户提交的当前页码数 :param total_count: 数据总数 :param url_prefix: 当前页面a标签的href的前缀 请求的URL :param per_page: 每个页面显示的数据数量 :param max_page: 页面上最多显示几个页码 """ self.url_prefix = url_prefix self.max_page = max_page # self.per_page = per_page # 每一页显示多少条数据 # 总共需要多少页码来展示 total_page, m = divmod(total_count, per_page) if m: total_page += 1 self.total_page = total_page try: page_num = int(page_num) # 如果输入的最大页数超过了最大页码,默认返回最后一页 if page_num > total_page: page_num = total_page except Exception as e: # 当输入的页码不是正经数字的时候,默认返回第一页 page_num = 1 self.page_num = page_num # 定义两个变量保存数据从哪儿取到哪儿 if total_count: self.data_start = (page_num - 1) * self.per_page else: # 如果数据库没有数据返回第一页 self.data_start=0 self.data_end = page_num * self.per_page # 页面上总共展示多少页码 if total_page < self.max_page: self.max_page = total_page # 页面上展示的页码从哪儿开始 page_start = page_num - (self.max_page // 2) # 页面上展示的页码到哪儿结束 page_end = page_num + (self.max_page // 2) if page_start <= 1: page_start = 1 page_end = self.max_page if page_end >= total_page: page_end = total_page page_start = total_page - self.max_page + 1 self.page_start = page_start self.page_end = page_end @property def start(self): return self.data_start @property def end(self): return self.data_end # 自己拼接分页的HTML代码 def page_html(self): html_str_list = [] # 添加首页 tmp = '<li><a href="{}?page=1">首页</a></li>'.format(self.url_prefix) html_str_list.append(tmp) # 添加上一页 如果上一页为第一页则不可用 if self.page_num <= 1: tmp = '<li class="disabled"><a href="#"><span aria-hidden="true">«</span></a></li>' else: tmp = '<li><a href="{0}?page={1}" aria-label="Previous">' \ '<span aria-hidden="true">«</span></a></li>'.format(self.url_prefix, self.page_num - 1) html_str_list.append(tmp) for i in range(self.page_start, self.page_end + 1): if i == self.page_num: tmp = '<li class="active"><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i) else: tmp = '<li><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i) html_str_list.append(tmp) # 添加下一页 如果下一页为最后一页则不可用 if self.page_num >= self.total_page: tmp = '<li class="disabled"><a href="#"><span aria-hidden="true">»</span></a></li>' else: tmp = '<li><a href="{0}?page={1}"><span aria-hidden="true">»</span></a></li>'.format(self.url_prefix, self.page_num + 1) html_str_list.append(tmp) # 添加尾页 tmp = '<li><a href="{0}?page={1}">尾页</a></li>'.format(self.url_prefix, self.total_page) html_str_list.append(tmp) page_html = ''.join(html_str_list) return page_html
def author(request): # 从URL中取当前访问的页码数 page_num = request.GET.get('page') # 比len(models.Publisher.objects.all())更高效 # 取到当前数据库数据的个数 total_count = models.Author.objects.all().count() # 实例化一个分页对象 page = Page(page_num, total_count,url_prefix='/author/',per_page=10, max_page=7) # 取到当前每页要展示的数据 all_author = models.Author.objects.all()[page.start:page.end] # 取到自定义分页的代码 page_html = page.page_html() return render(request, 'author.html', {'all_author': all_author, 'page_html': page_html})
<!DOCTYPE html> <html lang="zh-CN"> <head> <meta http-equiv="content-Type" charset="UTF-8"> <meta http-equiv="x-ua-compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <title>Title</title> {% load static %} <link rel="stylesheet" href="{% static 'bootstrap/css/bootstrap.min.css' %}"> </head> <body> <div class="container"> <table class="table table-bordered"> <thead> <tr> <th>序号</th> <th>id</th> <th>书名</th> <th>价格</th> </tr> </thead> <tbody> {% for author in all_author %} <tr> <td>{{ forloop.counter }}</td> <td>{{ author.id }}</td> <td>{{ author.name }}</td> </tr> {% endfor %} </tbody> </table> <nav aria-label="Page navigation"> <ul class="pagination"> {{ page_html|safe }} </ul> </nav> </div> </body> </html>
Django内置分页
from django.shortcuts import render from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger L = [] for i in range(999): L.append(i) def index(request): current_page = request.GET.get('p') paginator = Paginator(L, 10) # per_page: 每页显示条目数量 # count: 数据总个数 # num_pages:总页数 # page_range:总页数的索引范围，如: (1,10),(1,200) # page: page对象 try: posts = paginator.page(current_page) # has_next 是否有下一页 # next_page_number 下一页页码 # has_previous 是否有上一页 # previous_page_number 上一页页码 # object_list 分页之后的数据列表 # number 当前页 # paginator paginator对象 except PageNotAnInteger: posts = paginator.page(1) except EmptyPage: posts = paginator.page(paginator.num_pages) return render(request, 'index.html', {'posts': posts})
<!DOCTYPE html> <html> <head lang="en"> <meta charset="UTF-8"> <title></title> </head> <body> <ul> {% for item in posts %} <li>{{ item }}</li> {% endfor %} </ul> <div class="pagination"> <span class="step-links"> {% if posts.has_previous %} <a href="?p={{ posts.previous_page_number }}">Previous</a> {% endif %} <span class="current"> Page {{ posts.number }} of {{ posts.paginator.num_pages }}. </span> {% if posts.has_next %} <a href="?p={{ posts.next_page_number }}">Next</a> {% endif %} </span> </div> </body> </html>