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DAY18-Django之分页和中间件
阅读量:6283 次
发布时间:2019-06-22

本文共 19794 字,大约阅读时间需要 65 分钟。

分页

Django的分页器(paginator)

view

from django.shortcuts import render,HttpResponse# Create your views here.from app01.models import *from django.core.paginator import Paginator, EmptyPage, PageNotAnIntegerdef index(request):    '''    批量导入数据:    Booklist=[]    for i in range(100):        Booklist.append(Book(title="book"+str(i),price=30+i*i))    Book.objects.bulk_create(Booklist)    '''    '''分页器的使用:    book_list=Book.objects.all()    paginator = Paginator(book_list, 10)    #把所有数据按10条一页分    print("count:",paginator.count)           #数据总数    print("num_pages",paginator.num_pages)    #总页数    print("page_range",paginator.page_range)  #页码的列表range(1,8)    page1=paginator.page(1) #第1页的page对象    for i in page1:         #遍历第1页的所有数据对象        print(i)    print(page1.object_list) #第1页的所有数据    page2=paginator.page(2)    print(page2.has_next())            #是否有下一页    print(page2.next_page_number())    #下一页的页码    print(page2.has_previous())        #是否有上一页    print(page2.previous_page_number()) #上一页的页码    # 抛错    #page=paginator.page(12)   # error:EmptyPage    #page=paginator.page("z")   # error:PageNotAnInteger    '''    book_list=Book.objects.all()    paginator = Paginator(book_list, 10)    page = request.GET.get('page',1)     #如果get请求的page为空,则使用默认值1    currentPage=int(page)    try:        print(page)        book_list = paginator.page(page)    except PageNotAnInteger:        book_list = paginator.page(1)    except EmptyPage:        book_list = paginator.page(paginator.num_pages)    return render(request,"index.html",{
"book_list":book_list,"paginator":paginator,"currentPage":currentPage})

 

index.html:

    
Title

分页器

    {% for book in book_list %}
  • {
    { book.title }} -----{
    { book.price }}
  • {% endfor %}

扩展

def index(request):    book_list=Book.objects.all()    paginator = Paginator(book_list, 15)    page = request.GET.get('page',1)    currentPage=int(page)    #  如果页数十分多时,换另外一种显示方式    if paginator.num_pages>30:        if currentPage-5<1:            pageRange=range(1,11)        elif currentPage+5>paginator.num_pages:            pageRange=range(currentPage-5,paginator.num_pages+1)        else:            pageRange=range(currentPage-5,currentPage+5)    else:        pageRange=paginator.page_range    try:        print(page)        book_list = paginator.page(page)    except PageNotAnInteger:        book_list = paginator.page(1)    except EmptyPage:        book_list = paginator.page(paginator.num_pages)    return render(request,"index.html",locals())

 自己写的low版:

from django.shortcuts import render,HttpResponse,redirectfrom app01.models import Bookfrom django.core.paginator import Paginator, EmptyPage, PageNotAnInteger# Create your views here.def index(request):    #插入数据    # obj_list=[]    # for i in range(1,101):    #     obj=Book(title='book%s'%i,price=i*i)    #     obj_list.append(obj)    # Book.objects.bulk_create(obj_list)    # return HttpResponse("ok")    book_list=Book.objects.all()    paginator=Paginator(book_list,5)    currentPage=request.GET.get("page",1)    if not currentPage.isdigit() or currentPage=="0":        currentPage=1    currentPage=int(currentPage)    if currentPage > paginator.num_pages:        currentPage=paginator.num_pages    book_list=paginator.page(currentPage)    start=currentPage-3    if start<2:        start=2    end=start+7    if end>paginator.num_pages:        end=paginator.num_pages    if end-7>2:        start=end-7    page_range=range(start,end)    return render(request,"index.html",locals())
views.py
    
Title
{% for book in book_list %}
{
{ book.title }}----->{
{ book.price }}
{% endfor %}
index.html

 

自定义分页器

"""分页组件使用示例:    obj = Pagination(request.GET.get('page',1),len(USER_LIST),request.path_info)    page_user_list = USER_LIST[obj.start:obj.end]    page_html = obj.page_html()    return render(request,'index.html',{'users':page_user_list,'page_html':page_html})"""class Pagination(object):    def __init__(self,current_page,all_count,base_url,per_page_num=2,pager_count=11):        """        封装分页相关数据        :param current_page: 当前页        :param all_count:    数据库中的数据总条数        :param per_page_num: 每页显示的数据条数        :param base_url: 分页中显示的URL前缀        :param pager_count:  最多显示的页码个数        """        try:            current_page = int(current_page)        except Exception as e:            current_page = 1        if current_page <1:            current_page = 1        self.current_page = current_page        self.all_count = all_count        self.per_page_num = per_page_num        self.base_url = base_url        # 总页码        all_pager, tmp = divmod(all_count, per_page_num)        if tmp:            all_pager += 1        self.all_pager = all_pager        self.pager_count = pager_count        self.pager_count_half = int((pager_count - 1) / 2)    @property    def start(self):        return (self.current_page - 1) * self.per_page_num    @property    def end(self):        return self.current_page * self.per_page_num    def page_html(self):        # 如果总页码 < 11个:        if self.all_pager <= self.pager_count:            pager_start = 1            pager_end = self.all_pager + 1        # 总页码  > 11        else:            # 当前页如果<=页面上最多显示11/2个页码            if self.current_page <= self.pager_count_half:                pager_start = 1                pager_end = self.pager_count + 1            # 当前页大于5            else:                # 页码翻到最后                if (self.current_page + self.pager_count_half) > self.all_pager:                    pager_end = self.all_pager + 1                    pager_start = self.all_pager - self.pager_count + 1                else:                    pager_start = self.current_page - self.pager_count_half                    pager_end = self.current_page + self.pager_count_half + 1        page_html_list = []        first_page = '
  • 首页
  • ' % (self.base_url,1,) page_html_list.append(first_page) if self.current_page <= 1: prev_page = '
  • 上一页
  • ' else: prev_page = '
  • 上一页
  • ' % (self.base_url,self.current_page - 1,) page_html_list.append(prev_page) for i in range(pager_start, pager_end): if i == self.current_page: temp = '
  • %s
  • ' % (self.base_url,i, i,) else: temp = '
  • %s
  • ' % (self.base_url,i, i,) page_html_list.append(temp) if self.current_page >= self.all_pager: next_page = '
  • 下一页
  • ' else: next_page = '
  • 下一页
  • ' % (self.base_url,self.current_page + 1,) page_html_list.append(next_page) last_page = '
  • 尾页
  • ' % (self.base_url,self.all_pager,) page_html_list.append(last_page) return ''.join(page_html_list)

    自定义分页(葫芦版)

    data = []for i in range(1, 302):    tmp = {
    "id": i, "name": "alex-{}".format(i)} data.append(tmp)print(data)def user_list(request): # user_list = data[0:10] # user_list = data[10:20] try: current_page = int(request.GET.get("page")) except Exception as e: current_page = 1 per_page = 10 # 数据总条数 total_count = len(data) # 总页码 total_page, more = divmod(total_count, per_page) if more: total_page += 1 # 页面最多显示多少个页码 max_show = 11 half_show = int((max_show-1)/2) if current_page <= half_show: show_start = 1 show_end = max_show else: if current_page + half_show >= total_page: show_start = total_page - max_show show_end = total_page else: show_start = current_page - half_show show_end = current_page + half_show # 数据库中获取数据 data_start = (current_page - 1) * per_page data_end = current_page * per_page user_list = data[data_start:data_end] # 生成页面上显示的页码 page_html_list = [] # 加首页 first_li = '
  • 首页
  • ' page_html_list.append(first_li) # 加上一页 if current_page == 1: prev_li = '
  • 上一页
  • ' else: prev_li = '
  • 上一页
  • '.format(current_page - 1) page_html_list.append(prev_li) for i in range(show_start, show_end+1): if i == current_page: li_tag = '
  • {0}
  • '.format(i) else: li_tag = '
  • {0}
  • '.format(i) page_html_list.append(li_tag) # 加下一页 if current_page == total_page: next_li = '
  • 下一页
  • ' else: next_li = '
  • 下一页
  • '.format(current_page+1) page_html_list.append(next_li) # 加尾页 page_end_li = '
  • 尾页
  • '.format(total_page) page_html_list.append(page_end_li) page_html = "".join(page_html_list) return render(request, "user_list.html", {
    "user_list": user_list, "page_html": page_html})
    稳扎稳打版

     

    class Pagination(object):    def __init__(self, current_page, total_count, base_url, per_page=10, max_show=11):        """        :param current_page: 当前页        :param total_count: 数据库中数据总数        :param per_page: 每页显示多少条数据        :param max_show: 最多显示多少页        """        try:            current_page = int(current_page)        except Exception as e:            current_page = 1        self.current_page = current_page        self.total_count = total_count        self.base_url = base_url        self.per_page = per_page        self.max_show = max_show        # 总页码        total_page, more = divmod(total_count, per_page)        if more:            total_page += 1                half_show = int((max_show - 1) / 2)        self.half_show = half_show        self.total_page = total_page    @property    def start(self):        return (self.current_page - 1) * self.per_page    @property    def end(self):        return self.current_page * self.per_page    def page_html(self):        if self.current_page <= self.half_show:            show_start = 1            show_end = self.max_show        else:            if self.current_page + self.half_show >= self.total_page:                show_start = self.total_page - self.max_show                show_end = self.total_page            else:                show_start = self.current_page - self.half_show                show_end = self.current_page + self.half_show                # 生成页面上显示的页码        page_html_list = []        # 加首页        first_li = '
  • 首页
  • '.format(self.base_url) page_html_list.append(first_li) # 加上一页 if self.current_page == 1: prev_li = '
  • 上一页
  • ' else: prev_li = '
  • 上一页
  • '.format(self.base_url, self.current_page - 1) page_html_list.append(prev_li) for i in range(show_start, show_end + 1): if i == self.current_page: li_tag = '
  • {1}
  • '.format(self.base_url, i) else: li_tag = '
  • {1}
  • '.format(self.base_url, i) page_html_list.append(li_tag) # 加下一页 if self.current_page == self.total_page: next_li = '
  • 下一页
  • ' else: next_li = '
  • 下一页
  • '.format(self.base_url, self.current_page + 1) page_html_list.append(next_li) # 加尾页 page_end_li = '
  • 尾页
  • '.format(self.base_url, self.total_page) page_html_list.append(page_end_li) return "".join(page_html_list)
    封装保存版

     

    def user_list(request):    pager = Pagination(request.GET.get("page"), len(data), request.path_info)    user_list = data[pager.start:pager.end]    page_html = pager.page_html()    return render(request, "user_list.html", {
    "user_list": user_list, "page_html": page_html})

    Django内置分页

    from django.shortcuts import renderfrom django.core.paginator import Paginator, EmptyPage, PageNotAnIntegerL = []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})
    内置分页view部分
        
      {
      % for item in posts %}
    • {
      { item }}
    • {
      % endfor %}
    内置分页HTML部分

     

     

    中间件

    中间件的概念

    中间件顾名思义,是介于request与response处理之间的一道处理过程,相对比较轻量级,并且在全局上改变django的输入与输出。因为改变的是全局,所以需要谨慎实用,用不好会影响到性能。

    Django的中间件的定义:

    #Middleware is a framework of hooks into Django’s request/response processing. 
    It’s a light, low-level “plugin” system for globally altering Django’s input or output.

     

    如果你想修改请求,例如被传送到view中的HttpRequest对象。 或者你想修改view返回的HttpResponse对象,这些都可以通过中间件来实现。

    可能你还想在view执行之前做一些操作,这种情况就可以用 middleware来实现。

    大家可能频繁在view使用request.user吧。 Django想在每个view执行之前把user设置为request的属性,于是就用了一个中间件来实现这个目标。所以Django提供了可以修改request 对象的中间件 AuthenticationMiddleware

    Django默认的Middleware

    MIDDLEWARE = [    'django.middleware.security.SecurityMiddleware',    'django.contrib.sessions.middleware.SessionMiddleware',    'django.middleware.common.CommonMiddleware',    'django.middleware.csrf.CsrfViewMiddleware',    'django.contrib.auth.middleware.AuthenticationMiddleware',    'django.contrib.messages.middleware.MessageMiddleware',    'django.middleware.clickjacking.XFrameOptionsMiddleware',]

    每一个中间件都有具体的功能。

    自定义中间件

    中间件中一共有四个方法:

    process_requestprocess_viewprocess_exceptionprocess_response

    process_request,process_response

    当用户发起请求的时候会依次经过所有的的中间件,这个时候的请求时process_request,最后到达views的函数中,views函数处理后,在依次穿过中间件,这个时候是process_response,最后返回给请求者。

    上述截图中的中间件都是django中的,我们也可以自己定义一个中间件,我们可以自己写一个类,但是必须继承MiddlewareMixin

    需要导入

    from django.utils.deprecation import MiddlewareMixin

    注意,自定义的中间件模块名称和存放位置也不用固定,也可以放到具体应用文件夹中.

    in views:

    def index(request):    print("view函数...")    return HttpResponse("OK")

    in Mymiddlewares.py:

    from django.utils.deprecation import MiddlewareMixinfrom django.shortcuts import HttpResponseclass Md1(MiddlewareMixin):    def process_request(self,request):        print("Md1请求")     def process_response(self,request,response):        print("Md1返回")        return responseclass Md2(MiddlewareMixin):    def process_request(self,request):        print("Md2请求")        #return HttpResponse("Md2中断")    def process_response(self,request,response):        print("Md2返回")        return response

    结果:

    Md1请求Md2请求view函数...Md2返回Md1返回

    注意:如果当请求到达请求2的时候直接不符合条件返回,即return HttpResponse("Md2中断"),程序将把请求直接发给中间件2返回,然后依次返回到请求者,结果如下:

    返回Md2中断的页面,后台打印如下:

    Md1请求Md2请求Md2返回Md1返回

     

    流程图如下:

    process_view

    process_view(self, request, callback, callback_args, callback_kwargs)

     

     Mymiddlewares.py修改如下

    from django.utils.deprecation import MiddlewareMixinfrom django.shortcuts import HttpResponseclass Md1(MiddlewareMixin):    def process_request(self,request):        print("Md1请求")        #return HttpResponse("Md1中断")    def process_response(self,request,response):        print("Md1返回")        return response    def process_view(self, request, callback, callback_args, callback_kwargs):        print("Md1view")class Md2(MiddlewareMixin):    def process_request(self,request):        print("Md2请求")        return HttpResponse("Md2中断")    def process_response(self,request,response):        print("Md2返回")        return response    def process_view(self, request, callback, callback_args, callback_kwargs):        print("Md2view")

    结果如下:

    Md1请求Md2请求Md1viewMd2viewview函数...Md2返回Md1返回

    下图进行分析上面的过程:

     

    当最后一个中间的process_request到达路由关系映射之后,返回到中间件1的process_view,然后依次往下,到达views函数,最后通过process_response依次返回到达用户。

    process_view可以用来调用视图函数:

    class Md1(MiddlewareMixin):    def process_request(self,request):        print("Md1请求")        #return HttpResponse("Md1中断")    def process_response(self,request,response):        print("Md1返回")        return response    def process_view(self, request, callback, callback_args, callback_kwargs):        # return HttpResponse("hello")        response=callback(request,*callback_args,**callback_kwargs)        return response

    结果如下:

    Md1请求Md2请求view函数...Md2返回Md1返回

    注意:process_view如果有返回值,会越过其他的process_view以及视图函数,但是所有的process_response都还会执行。

    process_exception

    process_exception(self, request, exception)

    示例修改如下:

    class Md1(MiddlewareMixin):    def process_request(self,request):        print("Md1请求")        #return HttpResponse("Md1中断")    def process_response(self,request,response):        print("Md1返回")        return response    def process_view(self, request, callback, callback_args, callback_kwargs):        # return HttpResponse("hello")        # response=callback(request,*callback_args,**callback_kwargs)        # return response        print("md1 process_view...")    def process_exception(self):        print("md1 process_exception...")class Md2(MiddlewareMixin):    def process_request(self,request):        print("Md2请求")        # return HttpResponse("Md2中断")    def process_response(self,request,response):        print("Md2返回")        return response    def process_view(self, request, callback, callback_args, callback_kwargs):        print("md2 process_view...")    def process_exception(self):        print("md1 process_exception...")

    结果如下:

    Md1请求Md2请求md1 process_view...md2 process_view...view函数...Md2返回Md1返回

    流程图如下:

    当views出现错误时:

      将md2的process_exception修改如下:

    def process_exception(self,request,exception):        print("md2 process_exception...")        return HttpResponse("error")

    结果如下:

    Md1请求Md2请求md1 process_view...md2 process_view...view函数...md2 process_exception...Md2返回Md1返回

     

    转载于:https://www.cnblogs.com/guoyunlong666/p/8996907.html

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