自定义分页
- 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
import os if __name__ == '__main__': os.environ.setdefault("DJANGO_SETTINGS_MODULE", "new_pagedemo.settings") import django django.setup() from app01 import models # 列表生成式, 批量生成数据 create_list = (models.Book(title="book_%s" % i, price=i * i) for i in range(500)) # bulk_create()创建大量数据时使用 models.Book.objects.bulk_create(create_list)
学习研究版
def book_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.Book.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 + 1 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 book_list = models.Book.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="/book_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="/book_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="/book_list/?page={0}">{0}</a></li>'.format(i) else: li_tag = '<li><a href="/book_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="/book_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="/book_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, "book_list.html", {"book_list": book_list, "page_html": page_html})
<!DOCTYPE html> <html lang="zh-CN"> <head> <meta charset="utf-8"> <meta name="description" content=""> <meta name="author" content=""> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="/static/bootstrap/css/bootstrap.css"> <title>title</title> </head> <body> <div class="container"> <div class="row"> <table class="table table-bordered"> <thead> <tr> <th>ID</th> <th>title</th> <th>price</th> </tr> </thead> <tbody> {% for book in book_list %} <tr> <td>{{ book.id }}</td> <td>{{ book.title }}</td> <td>{{ book.price }}</td> </tr> {% endfor %} </tbody> </table> <nav aria-label="Page navigation"> <ul class="pagination"> {{ page_html|safe }} </ul> </nav> </div> </div> </body> </html>
封装保存
学习研究的例子，只能用于一个模型上，所以我们把它封装成一个组件让其它模型也可以使用
封装保存成组件
utils/mypage.py
class Page(): def __init__(self, page_num, total_count, url_prefix, per_page=10, max_page=11): """ :param page_num: 当前页码数 :param total_count: 数据总数 :param url_prefix: a标签href的前缀 :param per_page: 每页显示多少条数据 :param max_page: 页面上最多显示几个页码 """ self.url_prefix = url_prefix self.max_page = max_page # 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) # 如果输入的页码数超过了最大的页码数，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 默认返回第一页的数据 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 self.data_start = (page_num - 1) * 10 self.data_end = page_num * 10 # 页面上总共展示多少页码 if total_page < self.max_page: self.max_page = total_page half_max_page = self.max_page // 2 # 页面上展示的页码从哪儿开始 page_start = page_num - half_max_page # 页面上展示的页码到哪儿结束 page_end = page_num + half_max_page # 如果当前页减一半 比1还小 if page_start <= 1: page_start = 1 page_end = self.max_page # 如果 当前页 加 一半 比总页码数还大 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 def page_html(self): # 自己拼接分页的HTML代码 html_str_list = [] # 加上第一页 html_str_list.append('<li><a href="{}?page=1">首页</a></li>'.format(self.url_prefix)) # 判断一下 如果是第一页，就没有上一页 if self.page_num <= 1: html_str_list.append( '<li class="disabled"><a href="#"><span aria-hidden="true">«</span></a></li>'.format( self.page_num - 1)) else: # 加一个上一页的标签 html_str_list.append( '<li><a href="{}?page={}"><span aria-hidden="true">«</span></a></li>'.format(self.url_prefix, self.page_num - 1)) for i in range(self.page_start, self.page_end + 1): # 如果是当前页就加一个active样式类 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) # 加一个下一页的按钮 # 判断，如果是最后一页，就没有下一页 if self.page_num >= self.total_page: html_str_list.append('<li class="disabled"><a href="#"><span aria-hidden="true">»</span></a></li>') else: html_str_list.append( '<li><a href="{}?page={}"><span aria-hidden="true">»</span></a></li>'.format(self.url_prefix, self.page_num + 1)) # 加最后一页 html_str_list.append('<li><a href="{}?page={}">尾页</a></li>'.format(self.url_prefix, self.total_page)) page_html = "".join(html_str_list) return page_html
使用示例
from django.shortcuts import render from app01 import models def book_list(request): # 从URL中取参数,用户想访问的是哪一页 page_num = request.GET.get("page") # 总数据有多少条 total_count = models.Book.objects.all().count() from utils.mypage import Page page_obj = Page(page_num,total_count,url_prefix='/book_list/') book_list = models.Book.objects.all()[page_obj.data_start:page_obj.data_end] return render(request, 'book_list.html', {"book_list": book_list, "page_html": page_obj.page_html()}) def depts(request): # 从URL取参数 page_num = request.GET.get("page") # 总数据是多少 total_count = models.Dept.objects.all().count() from utils.mypage import Page page_obj = Page(page_num, total_count, per_page=10, url_prefix="/depts/", max_page=11, ) ret = models.Dept.objects.all()[page_obj.start:page_obj.end] return render(request, "dept.html", {"depts": ret, "page_html": page_obj.page_html()})