NoReverseMatch error during url

Question

New to Django framework. Mostly reading through documentations. But this one i am unable to crack.

Trying to add a URL to an headline, that will be forwarded to the 'headlines' post.

The Error:

NoReverseMatch at / Reverse for 'assignment_detail' with arguments '('',)' not found. 1 pattern(s) tried: ['assignment_detail/'] Request Method: GET Request URL: http://127.0.0.1:8000/ Django Version: 2.0.2 Exception Type: NoReverseMatch Exception Value: Reverse for 'assignment_detail' with arguments '('',)' not found. 1 pattern(s) tried: ['assignment_detail/'] Exception Location: C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib\\site-packages\\django\\urls\\resolvers.py in _reverse_with_prefix, line 632 Python Executable: C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\Scripts\\python.exe Python Version: 3.6.2 Python Path:
['C:\\Users\\internit\\Dropbox\\Python\\codepython\\codepython', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\Scripts\\python36.zip', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\DLLs', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\Scripts', 'c:\\program files (x86)\\python36-32\\Lib', 'c:\\program files (x86)\\python36-32\\DLLs', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env', 'C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib\\site-packages'] Server time: Thu, 8 Feb 2018 14:53:07 +0000 Error during template rendering In template C:\\Users\\internit\\Dropbox\\Python\\codepython\\codepython\\codepython\\templates\\base.html, error at line 0

Reverse for 'assignment_detail' with arguments '('',)' not found. 1 pattern(s) tried: ['assignment_detail/'] 1 {% load static %} 2 3 4 5 6 7 8 9 10 CODEPYTHON.NET Traceback Switch to copy-and-paste view C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib\\site-packages\\django\\core\\handlers\\exception.py in inner response = get_response(request) ... ▶ Local vars C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib\\site-packages\\django\\core\\handlers\\base.py in _get_response response = self.process_exception_by_middleware(e, request) ... ▶ Local vars C:\\Users\\internit\\Dropbox\\Python\\codepython\\env\\lib\\site-packages\\django\\core\\handlers\\base.py in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) ... ▶ Local vars C:\\Users\\internit\\Dropbox\\Python\\codepython\\codepython\\home\\views.py in home return render(request, 'home.html', {'post':post}) ... ▶ Local vars

home/urls.py

from django.conf.urls import url
from django.conf import settings
from django.conf.urls.static import static
from codepython.posts import views
from posts import views as ps


app_name ='home'

urlpatterns = [
    url(r'^$/', views.create, name='create'),
    url(r'(?P<pk>\d+)/$', views.home, name='home'),
    url(r'(?P<pk>\d+)/$', views.userposts, name='userposts')
    url(r'^posts/(?P<post_id>[0-9]+)/$', ps.assignment_detail, name='assignment_detail'),


]+ static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)

home/views.py

from django.shortcuts import render, get_object_or_404
from django.apps import apps


# Create your views here.

def home(request):
    posts = apps.get_model("posts", "Post")
    post = posts.objects.all().order_by('-pub_date')[0:6]

    return render(request, 'home.html', {'post':post})

def assignment_detail(request, post_id):
    posts = apps.get_model('posts', 'Post')
    post = get_object_or_404(posts, pk=post_id)

    return render(request, "assignment_detail.html", {'post': post})

home.html

<div class="row">
    {% for post in post.all %}
        <div class="col-md-4">
            <div class="thumbnail">

                <div class="caption">
                    <p>Level: {{post.assignment_level}}</p>
                    <a href="{% url 'assignment_detail' post_id %}"><h3>{{ post.title }}</h3></a>
                    <p>by {{post.author}} from {{post.pub_date}}</p>
                    <h4>{{post.assignment_body}}</h4>

                    <p><a href="#" class="btn btn-primary" role="button">Read...</a></p>
                </div>
            </div>
        </div>
    {% endfor %}
</div>
{% endblock%}

myproject/urls.py

url(r'^assignment_detail/', views.assignment_detail,name='assignment_detail'),

What am I missing here. Thank you in advance.

Answer 1

Your url does not imply that you have to pass an id, but you're passing one in the template:

<a href="{% url 'assignment_detail' post_id %}"><h3>{{ post.title }}</h3></a>

It should be:

url(r'^assignment_detail/(?P<post_id>[0-9]+)', views.assignment_detail,name='assignment_detail'),

Answer 2

That error is Django telling you that it can't find any URLs named 'assignment_detail' that have an argument to pass in.

This is because your url entry in myproject/urls.py is missing the argument ( post_id ) that you use in your view. You'll need to update that url line to something similar to this:

url(r'^assignment_detail/(?P<post_id>[0-9]+)/$', views.assignment_detail, name='assignment_detail'),

The change at the end of the URL adds a named regular expression to capture the post_id value which will then be passed into the view.

Looking at your template code, you'll need to update your {% url %} block to use post.id (notice period) not post_id