Django错误：匹配查询不存在

Question

我正在开发一个博客项目，我收到“匹配查询不存在”错误。我尝试使用try块认为模型类可能没有返回任何值。因此，修改了我的views.py如下： -

from django.shortcuts import render, HttpResponseRedirect
from django.contrib.auth import authenticate, login, logout
from django.contrib.auth.models import User
from django.contrib.auth.hashers import make_password
from django.db.models import Q
from .forms import *

# Create your views here.

def home(request):
    print("I am home")
    try:
        blog_data = BlogPost.objects.all()
        print("blog_data", blog_data)
    except BlogPost.DoesNotExist:
        blog_data = None
        print("blog_data", blog_data)
    try:
        last_element = BlogPost.objects.filter(id = len(blog_data))[0]
        print("last_element", last_element)
    except BlogPost.DoesNotExist:
        last_element = None
        print("last_element", last_element)
    tags_list = BlogPost.objects.values_list("tags", flat = True).distinct()
    #tags_list = BlogPost.objects.all().distinct()
    context = {'blog_data':blog_data, "last_element":last_element, "tags_list":tags_list}
    #last_element = list(BlogPost.objects.all().reverse()[0])
    print("last_element",last_element, "blog_data",blog_data,"context",context)
    return render(request, 'blog/home.html', context)

# def home(request):   
#     blog_data = BlogPost.objects.all()
#     context = {'blog_data':blog_data}   
#     print('context', context)
#     last_element = BlogPost.objects.all().reverse()[0]
#     #last_element = BlogPost.objects.all().reverse()[0]
#     return render(request, 'blog/home.html', context)
def new_post(request):      
    if request.method == 'POST':        
        form = BlogForm(data = request.POST)
        if form.is_valid():
            form.save()
            return HttpResponseRedirect('home')
    else:
        form = BlogForm()       
    return render(request, 'blog/blogform.html', {'form':form })

def login_user(request): 
    username = password = ''
    state = "Please log in"    
    if request.POST:        
        username = request.POST.get('Username')
        password = request.POST.get('Password')         
        user = authenticate(username=username, password=password)              
        if user is not None:
            if user.is_active:
                login(request, user)
                state = "You're successfully logged in!"
                return HttpResponseRedirect('/blog/home')
            else:
                state = "Your account is not active, please contact the site admin."
        else:
            state = "Your username and/or password were incorrect."

    #return render_to_response('main/login.html',{'state':state, 'username': username})
    return render(request, "blog/login.html", {'state':state, 'username': username, 'next_page':"home.html"})
    #return HttpResponseRedirect("home.html")

def logout_user(request): 
    logout(request)
    return render(request,'blog/home.html')

def register_user(request):
    username = password = password_again = email = ''
    state = ''
    if request.method == 'POST':
        username = request.POST.get('Username')
        password = request.POST.get('Password')
        password_again = request.POST.get('Password_again')
        email = request.POST.get('Email')
        print('email', email)
        if password == password_again:
            password = make_password(password, salt = None, hasher = 'default')
        else:
            state = "Password and password re-entered do not match, please try again..."
            return HttpResponseRedirect('login')
        print("at 63")
        try:
            user = User.objects.get(username = username)
            print('user at 67', user)
        except Exception as e:
            print("Error is :", e)
            user = None
        print("user", user)
        try:
            emailID = User.objects.get(email = email)
            print("emailID", emailID)
        except Exception as e:
            print("Error is :", e)
            emailID = None
            print("emailID exception", emailID)        
        if user is not None:
            state = 'Username already exists, please try another one...'
        else:
            if emailID is None:
                new_user = User(username = username, password = password, email = email)
                ##Adding new logic for securityQAs vvv
                #new_SQA = SecurityQA(user_email = email, security_question = security_question, security_answer = security_answer)
                ##Adding new logic for securityQAs ^^^
                new_user.save()
                #new_SQA.save()
                state = 'You are successfully registered.. Thanks'
                return HttpResponseRedirect('login')
            else:
                state = "Email ID already registered, try a new one.."
                print('state at else', state)
                #return HttpResponseRedirect('login')

    return render(request, "blog/register.html", {'state':state, 'username':username, 'next_page':'home.html'})

def forgot_password(request):
    pass
def comment_posted(request):
    return render(request, "blog/comment_posted.html")

def blog_search(request):
    qset = Q()
    keyword = ''
    keyword = request.POST.get('keyword')
    print("keyword", keyword)
    for word in keyword.split():
        qset |= (Q(title__contains = word)|Q(description__contains = word))

    print('qset', qset)
    result = BlogPost.objects.filter(qset)
    context = {'result':result}
    return render(request, 'blog/blog_search.html', context)

另外，找到我的models.py

from django.db import models
from django.contrib.auth.models import User
#from django.core.files.storage import FileSystemStorage

#fs = FileSystemStorage(location='E:\django\myblog\\blog\uploaded images')
# Create your models here.
class BlogPost(models.Model):
    title = models.CharField(max_length = 30)
    posted_by = models.CharField(max_length = 30)
    posted_on = models.DateTimeField(auto_now_add = True)
    description = models.CharField(max_length = 200)
    comment = models.CharField(max_length = 150) 
    tags = models.CharField(max_length=50, default = "notag")
    image = models.ImageField(upload_to = 'uploaded_images', default = None, null = True, blank = True)

    def __str__(self):
        #return "{0} : {1}".format(self.title, self.description)
        return self.title

模板代码如下（home.html）。在这里，我收到错误行“{％get_comment_list for blog.blogpost last_element.id as comment_list％}”

{% load staticfiles %}
{%load comments%}
<!DOCTYPE html>
<html lang="en">

<head>

    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="">
    <meta name="author" content="">

    <title>Sourav's blog</title>

    <!-- Bootstrap Core CSS -->
    {%block styling%}
    <link href="{%static 'css/bootstrap.min.css'%}" rel="stylesheet">

    <!-- Custom CSS -->
    <link href="{%static 'css/blog-post.css'%}" rel="stylesheet">

    {%endblock styling%}

    <!-- HTML5 Shim and Respond.js IE8 support of HTML5 elements and media queries -->
    <!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
    <!--[if lt IE 9]>
        <script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
        <script src="https://oss.maxcdn.com/libs/respond.js/1.4.2/respond.min.js"></script>
    <![endif]-->

</head>

<body>

    <!-- Navigation -->
    <nav class="navbar navbar-inverse navbar-fixed-top" role="navigation">
        <div class="container">
            <!-- Brand and toggle get grouped for better mobile display -->
            <div class="navbar-header">
                <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1">
                    <span class="sr-only">Toggle navigation</span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>
                </button>
                <a class="navbar-brand" href="#">Ideate</a>
            </div>
            <!-- Collect the nav links, forms, and other content for toggling -->
            <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                <ul class="nav navbar-nav">
                    <li>
                        <a href="{%url 'blog_new_post'%}">New idea</a>
                    </li>
                    <!-- <li><a href="{%url 'blog_login'%}">Login</a></li> -->
                    {{user.is_authenticated}}
                    {% if user.is_authenticated %}
                    <li>
                        <a href="{%url 'blog_logout'%}">Logout</a>
                    </li>
                    {% else %}
                    <li>
                        <a href="{%url 'blog_login'%}">Login</a>
                    </li>
                    {% endif %}
                    <li>
                        <a href="#">Help</a>
                    </li>
                    {% if user.is_authenticated %}
                    <li>
                        <a href="#">Hi {{user.username}}</a>
                    </li>
                    {%else%}

                    {% endif %}
                </ul>
            </div>
            <!-- /.navbar-collapse -->
        </div>
        <!-- /.container -->
    </nav>

    <!-- Page Content -->
    <div class="container">

        <div class="row">

            <!-- Blog Post Content Column -->
            <div class="col-lg-8">

                <!-- Blog Post -->

                <!-- Title -->
                <h1>Idea Blog</h1>

                <!-- Author -->
                <p class="lead">
                    by <a href="#">Sourav</a>
                </p>

                <hr>

                <!-- Date/Time -->
                <p><span class="glyphicon glyphicon-time"></span> 
                Posted on
                <!-- {%for i in blog_data%} 
                    {{i.posted_on}}
                {%endfor%}</p> -->
                {{last_element.posted_on}}


                <hr>

                <!-- Preview Image -->
                <img class="img-responsive" src="http://placehold.it/900x300" alt="">

                <hr>

                <!-- Post Content -->
                <!-- <p>Below is the result</p> -->
                <!-- <p>{{blog_data}}</p> -->
                <p>

                    <!-- {%for i in blog_data%}                        
                       <h1>{{i.title}}</h1> 
                       <p>{{i.description}}</p>  

                    {%empty%}
                        <span>No data</span>
                    {%endfor%} -->
                    <!-- {{last_element}} -->
                    <h1>{{last_element.title}}</h1><span> posted by {{last_element.posted_by}}</span>
                    <p>Description : {{last_element.description}}</p>
                    {{last_element.image}}
                    <p>Tags : {{last_element.tags}}</p>

                    {% get_comment_count for blog.blogpost last_element.id as comment_count %}
                    <p>{{ comment_count }} comments have been posted.</p> 

                    {% get_comment_list for blog.blogpost 1 as comment_list %}
                    {% for comment in comment_list %}
                    <p>Posted by: {{ comment.user_name }} on {{ comment.submit_date }}</p>

                    <p>Comment: {{ comment.comment }}</p>

                    {% endfor %}


                    {% get_comment_form for blog.blogpost last_element.id as form %}
                    <!-- A context variable called form is created with the necessary hidden
                    fields, timestamps and security hashes -->
                    <table>
                      <form action="{% comment_form_target %}" method="post">
                        {% csrf_token %}
                        {{ form }}
                        <tr>
                          <td colspan="1">
                            <input type="submit" name="submit" value="Post">
                            <input type="submit" name="preview" value="Preview">
                            <input type="hidden" name="next" value="{% url 'comment_posted' %}" />
                          </td>
                        </tr>
                      </form>
                    </table>

                {% get_comment_list for blog.blogpost last_element.id as comment_list %}
                {%for comment in comment_list%}
                    <li><b>{{comment.name}}</b> has posted comment on {{comment.submit_date}} </li>
                        <ul><li>{{comment.comment}}</li></ul>
                    <a name="c{{ comment.id }}"></a>
                    <a href="{% get_comment_permalink comment %}">
                        see comment details
                    </a>
                {%endfor%}
                </p>               



                    </div>
                    <div class="col-md-4">

                <!-- Blog Search Well -->
                <form action = "{%url 'blog_search'%}" method = "POST">
                <div class="well">
                    <h4>Blog Search</h4>                    
                    <div class="input-group">                        
                        {%csrf_token%}
                        <input type="text" class="form-control" name = "keyword", placeholder = "Enter search keyword">
                        <span class="input-group-btn">
                            <button class="btn btn-default" type="submit">
                                <span class="glyphicon glyphicon-search"></span>
                        </button>
                        </span>                        
                    </div>                    
                    <!-- /.input-group -->
                </div>
                </form>

                <!-- Blog Categories Well -->
                <div class="well">
                    <h4>Tags</h4>
                    <div class="row">
                        <div class="col-lg-6">
                            <ul class="list-unstyled">
                                <!-- {%for a in tags_list%}
                                    <a href="">{{a}}</a>
                                {%endfor%} -->
                                <!-- {%for a in tags_list%}
                                    <a href="">{{a}}</a>
                                {%endfor%} -->
                                {%for a in tags_list%}
                                    <a href="">{{a}},</a>
                                {%endfor%}
                                <!-- <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li> -->
                            </ul>
                        </div>
                        <div class="col-lg-6">
                            <ul class="list-unstyled">
                                <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li>
                                <li><a href="#">Category Name</a>
                                </li>
                            </ul>
                        </div>
                    </div>
                    <!-- /.row -->
                </div>

                <!-- Side Widget Well -->
                <div class="well">
                    <h4>Side Widget Well</h4>
                    <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Inventore, perspiciatis adipisci accusamus laudantium odit aliquam repellat tempore quos aspernatur vero.</p>
                </div>

            </div>

        </div>
                </div>

            </div>

            <!-- Blog Sidebar Widgets Column -->

        <!-- /.row -->

        <hr>

        <!-- Footer -->
        <footer>
            <div class="row">
                <div class="col-lg-12">
                    <p>Copyright &copy; Your Website 2014</p>
                </div>
            </div>
            <!-- /.row -->
        </footer>

    </div>
    <!-- /.container -->

    <!-- jQuery -->
    {%block javascript%}
    <script src="{%static 'js/jquery.js'%}"></script>

    <!-- Bootstrap Core JavaScript -->
    <script src="{%static 'js/bootstrap.min.js'%}"></script>
    {%endblock javascript%}

</body>

</html>

当我加载我的主页（home.html）时，我没有遇到任何问题，但是，当我在登录后尝试注销时，我正面临错误。我的注销视图也在渲染home.html。但是，在这种情况下，它不起作用。请帮我解决这个问题。我被卡住了。

Answer 1

我的快速回答是注销视图功能没有提供home.html模板所需的上下文变量。请尝试重定向到主视图。