'Django - Reverse for '' not found. '' is not a valid view function or pattern name

I'm working on my project for a course and I'm totally stuck right now. I'm creating a website to sell products through paypal and the paypal return/cancel pages are not rendering properly. I've followed the examples in my lessons and checked the code a hundred times but obviously there is something I'm missing.

I'm getting an error when I go to products, click buy now, login to paypal and then either cancel the purchase or buy the product and return to merchant's page. paypal_return.html and paypal_cancel.html are 2 templates saved under templates/paypal/

Can anybody see what I'm missing?

Here you can see the full code https://github.com/IreneG5/spss_online

Traceback

Environment:


Request Method: GET
Request URL: http://127.0.0.1:8000/paypal-cancel/

Django Version: 1.11.4
Python Version: 2.7.12
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'django_forms_bootstrap',
 'paypal.standard.ipn',
 'home',
 'accounts',
 'paypal_store',
 'products']
Installed 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']


Template error:
In template C:\Users\irene\Documents\Full-Stack-Developer\Stream3\Project\spss_online\templates\base.html, error at line 10
   Reverse for '' not found. '' is not a valid view function or pattern name.   1 : {% load staticfiles %}
   2 : <!DOCTYPE html>
   3 : <html lang="en">
   4 : <head>
   5 :     <meta charset="UTF-8">
   6 :     <title>Buy SPSS Online</title>
   7 :     <meta name="viewport" content="width=device-width, initial-scale=1.0">
   8 :     <meta name="description" content="">
   9 :     <meta name="author" content="">
   10 :     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootswatch/3.3.7/cerulean/bootstrap.min.css">
   11 :     <link rel="stylesheet" href="{% static 'css/style.css' %}">
   12 : 
   13 : 
   14 : </head>
   15 : <body>
   16 : <div class="container">
   17 :     <div class='container-fluid'>
   18 :         <nav id="menu" class="navbar navbar-inverse">
   19 :             <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#myNavbar">
   20 :                 <span class="icon-bar"></span>


Traceback:

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\core\handlers\exception.py" in inner
  41.             response = get_response(request)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\core\handlers\base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\core\handlers\base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "C:\Users\irene\Documents\Full-Stack-Developer\Stream3\Project\spss_online\paypal_store\views.py" in paypal_cancel
  15.     return render(request, 'paypal/paypal_cancel.html', args)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\shortcuts.py" in render
  30.     content = loader.render_to_string(template_name, context, request, using=using)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\loader.py" in render_to_string
  68.     return template.render(context, request)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\backends\django.py" in render
  66.             return self.template.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render
  207.                     return self._render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in _render
  199.         return self.nodelist.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render
  990.                 bit = node.render_annotated(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render_annotated
  957.             return self.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\loader_tags.py" in render
  177.             return compiled_parent._render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in _render
  199.         return self.nodelist.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render
  990.                 bit = node.render_annotated(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render_annotated
  957.             return self.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\loader_tags.py" in render
  72.                 result = block.nodelist.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render
  990.                 bit = node.render_annotated(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\base.py" in render_annotated
  957.             return self.render(context)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\template\defaulttags.py" in render
  458.             url = reverse(view_name, args=args, kwargs=kwargs, current_app=current_app)

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\urls\base.py" in reverse
  91.     return force_text(iri_to_uri(resolver._reverse_with_prefix(view, prefix, *args, **kwargs)))

File "C:\Users\irene\virtualenv\spss_online_env\lib\site-packages\django\urls\resolvers.py" in _reverse_with_prefix
  497.         raise NoReverseMatch(msg)

Exception Type: NoReverseMatch at /paypal-cancel/
Exception Value: Reverse for '' not found. '' is not a valid view function or pattern name.

Solution 1:^[1]

When you use the url tag you should use quotes for string literals, for example:

{% url 'products' %}

At the moment product is treated like a variable and evaluates to '' in the error message.

Solution 2:^[2]

The syntax for specifying url is {% url namespace:url_name %}. So, check if you have added the app_name in urls.py.
In my case, I had misspelled the url_name. The urls.py had the following content path('<int:question_id>/', views.detail, name='question_detail') whereas the index.html file had the following entry <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>. Notice the incorrect name.

Solution 3:^[3]

I was receiving the same error when not specifying the app name before pattern name. In my case:

app-name : Blog

pattern-name : post-delete

reverse_lazy('Blog:post-delete') worked.

Solution 4:^[4]

Add store name to template like {% url 'app_name:url_name' %}

App_name = store

In urls.py, path('search', views.searched, name="searched"),

<form action="{% url 'store:searched' %}" method="POST">

Solution 5:^[5]

Specify app_name in the urls.py file of an app and use this app_name along with the string literal view name of the url in templates:

syntax --> {% url 'app_name:urlname' %}

app_name = "demo".   # right above url patterns in app
url_patterns = [
('login/', views.login, name = 'login')
]

<a href="{% url 'demo:login' %}".  # Use this in templatep

Note: use the app_name right above the url_patterns in urls.py file.

Solution 6:^[6]

Fix urlpatterns in urls.py file

For example, my app name is "simulator",

My URL pattern for login and logout looks like

urlpatterns = [
    ...
    ...
    url(r'^login/$', simulator.views.login_view, name="login"),
    url(r'^logout/$', simulator.views.logout_view, name="logout"),
    ...
    ...

]

Solution 7:^[7]

You can use one of these.

If you did not (app_name) This is the solution

in urls.py

urlpatterns = [
    path('', dashboard.as_view(), name='dashboard'),
]

in template.html

<a href="{% url 'dashboard' %}"></a>

If you did (app_name) This is the solution

in urls.py

app_name = 'Blog'
urlpatterns = [
    path('', dashboard.as_view(), name='dashboard'),
]

in template.html

<a href="{% url 'Blog:dashboard' %}"></a>

Solution 8:^[8]

In my case, what I did was a mistake in the url tag in the respective template. So, in my url tag I had something like

{% url 'polls:details' question.id %}

while in the views, I had written something like:

def details(request, question_id): code here

So, the first thing you might wanna check is whether things are spelled as they shoould be. The next thing then you can do is as the people above have suggested.

Solution 9:^[9]

In my case, this error occurred because I forgot to add app_name along with url_name. Below is my app urls.py

    app_name = "wikis"
    urlpatterns = [
        path("", views.index, name="index"),
        path("wiki/<str:name>", views.get_page, name="get_page"),
       ]

Below is my function's return statement where I forgot to put app_name in reverse URL

    return HttpResponseRedirect(reverse("get_page", kwargs={'name':title}))

Correct code would be

    return HttpResponseRedirect(reverse("wikis:get_page", kwargs={'name':title}))

Solution 10:^[10]

In my case, I don't put namespace_name in the url tag ex: {% url 'url_name or pattern name' %}. you have to specify the namespace_name like: {% url 'namespace_name:url_name or pattern name' %}.

Explanation: In project urls.py path('', include('blog.urls',namespace='blog')), and in app's urls.py you have to specify the app_name. like app_name = 'blog'. namespace_name is the app_name.

Solution 11:^[11]

*Always make sure when you use HttpResponseRedirect and reverse, the name you specify inside reverse is the same name you gave to your path inside urls.py

Thats the problem i had and i found out through trial and error*

Solution 12:^[12]

You can also get this error if you forget to add the app url in the project url

Example: Project/urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('app.urls')),
]

and you have a store/urls.py

so if you have html code in store/templates/store and you want to add in app/templates/app an a tag with the url to an html code in store/templates/store

You would have to include the store/urls.py in Project/urls.py

Project/urls.py

from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('', include('app.urls')),
    path('', include('store.urls')),
]

Solution 13:^[13]

I too faced the same issue while testing, for me it was caused when url was empty in html

<td><a href="{% url '' test.id %}"><i class="fa fa-times" aria-hidden="true"></i></a></td>

So after I changed it by putting the url name:

<td><a href="{% url 'task_delete' test.id %}"><i class="fa fa-times" aria-hidden="true"></i></a></td>

Solution 14:^[14]

If you dont define name in the path field, usually the error will come. e.g.: path('crud/',ABC.as_view(),name="crud")

Solution 15:^[15]

Give the same name in urls.py

 path('detail/<int:id>', views.detail, name="detail"),

Solution 16:^[16]

In my case, this error occurred due to a mismatched url name. e.g,

<form action="{% url 'test-view' %}" method="POST">

urls.py

path("test/", views.test, name='test-view'),

Solution 17:^[17]

*Always make sure when you use HttpResponseRedirect and reverse, the name you specify inside reverse is the same name you gave to your path inside urls.py

'return HttpResponseRedirect(reverse("index")) path("index/",views.index,name="index")'

Thats the problem i had and i found out through trial and error*

Solution 18:^[18]

I have faced the same problem. The mistake was I declared same name for multiple urlpatterns.

 path('file', views.sender, name='sender'),

Here the name should be different and unique for different url.

Solution 19:^[19]

Let's say in your template home.html you are having a form that does a POST request, like:

<form id="form_id" action = "{% url 'home' %}" method = "post" > .. </form>

In your urls.py you have

url(r'^$', views.home_view, name='home')

in your view, you can check the passed data from template like this.

def home_view(request): print(request.POST)

it is important in urls.py to declare a name='home' and on your action part on the form to include this url action = "{% url 'home' %}"

Solution 20:^[20]

I've been reading this for past two days to compare mine to see why it didn't work. it turns out a space between ":" matters: mine had a space between ":" and "index":

<a href="{% url 'namespace: index' %}">Home</a>

thought this worth mentioning in case someone like me scratching their heads in the future: No space around the colon, or anywhere before or after "namespace" and "index"

Solution 21:^[21]

The simple solution is

 path('detail/', views.detail, name="This_is_the_solution"),

you have to give the name value to the url,

<a href="{% url 'This_is_the_solution' %}"></a>

Solution 22:^[22]

On line 10 there's a space between s and t. It should be one word: stylesheet.

Solution 23:^[23]

The common error that I have find is when you forget to define your url in yourapp/urls.py

we don't want any suggetion!! solution plz..

Solution 24:^[24]

appname=demo url=/student

href="{% url 'demo:student' %}"

Make Sure you should not have space before or after : (colon)

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1
Solution 2	Aditya Mishra
Solution 3	Krishna
Solution 4	Kamar
Solution 5	Ank
Solution 6	Dartion
Solution 7	shoja
Solution 8	Varun Sharma
Solution 9	bguiz
Solution 10
Solution 11	Gesy Darati
Solution 12	AnonymousUser
Solution 13	Akshay
Solution 14	Aleksey Potapov
Solution 15	Raja Kumar More
Solution 16	shoaib21
Solution 17	Gesy Darati
Solution 18	Md. Babul Hasan
Solution 19	A.Ktns
Solution 20
Solution 21	Md Rakibul Islam
Solution 22	4b0
Solution 23	Community
Solution 24	sreekanth

'Django - Reverse for '' not found. '' is not a valid view function or pattern name

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