Why do I get an 404 Error in part 4 of the Django tutorial “Writing you first Django app”

I am trying to complete the Django tutorial: Writing your first Django app. I am currently stuck on part 4.

After updating my template polls/templates/polls/detail.html, rewriting my polls/views.py and creating a results.html located at polls/templates/polls/results.html, I ran the server and tried to go to http://127.0.0.1:8000/polls/1/, but I get this Error:

Page not found (404)
No Question matches the given query.
Request Method: GET
Request URL:    http://127.0.0.1:8000/polls/1/
Raised by:  polls.views.detail
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:

polls/ [name='index']
polls/ <int:question_id>/ [name='detail']
The current path, polls/1/, matched the last one.

You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.

JavaScript
​x
 
Page not found (404)
No Question matches the given query.
Request Method: GET
Request URL:    http://127.0.0.1:8000/polls/1/
Raised by:  polls.views.detail
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:
​
polls/ [name='index']
polls/ <int:question_id>/ [name='detail']
The current path, polls/1/, matched the last one.
​
You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page. 
​

I see that the error is raised by the html-file detail which looks like this:

<form action="{ url 'polls:vote' question.id }" method="post">
{ csrf_token }
<fieldset>
    <legend><h1>{{ question.question_text }}</h1></legend>

    { if error_message }<p><strong>{{ error_message }}</strong></p>{ endif }
    { for choice in question.choice_set.all }
        <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}">
        <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br>
    { endfor }
</fieldset>
<input type="submit" value="Vote">
</form>

JavaScript
 
<form action="{ url 'polls:vote' question.id }" method="post">
{ csrf_token }
<fieldset>
    <legend><h1>{{ question.question_text }}</h1></legend>
​
    { if error_message }<p><strong>{{ error_message }}</strong></p>{ endif }
    { for choice in question.choice_set.all }
        <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}">
        <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br>
    { endfor }
</fieldset>
<input type="submit" value="Vote">
</form>
​

My other two templates (html-files) index and result looks like this:

index.html:

{ if latest_question_list }
    <ul>
    { for question in latest_question_list }
        <li><a href="{ url 'polls:detail' question.id }">{{ question.question_text }}</a></li>
    { endfor }
    </ul>
{ else }
    <p>No polls are available.</p>
{ endif }

JavaScript
 
{ if latest_question_list }
    <ul>
    { for question in latest_question_list }
        <li><a href="{ url 'polls:detail' question.id }">{{ question.question_text }}</a></li>
    { endfor }
    </ul>
{ else }
    <p>No polls are available.</p>
{ endif }
​

results.html:

<h1>{{ question.question_text }}</h1>

<ul>
{ for choice in question.choice_set.all }
    <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{ endfor }
</ul>

<a href="{ url 'polls:detail' question.id }">Vote again?</a>

JavaScript
 
<h1>{{ question.question_text }}</h1>
​
<ul>
{ for choice in question.choice_set.all }
    <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{ endfor }
</ul>
​
<a href="{ url 'polls:detail' question.id }">Vote again?</a>
​

When I try to run just http://127.0.0.1:8000, I get this Error Message:

Page not found (404)
Request Method: GET
Request URL:    http://127.0.0.1:8000/
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:

polls/
admin/
The empty path didn’t match any of these.

You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.

JavaScript
 
Page not found (404)
Request Method: GET
Request URL:    http://127.0.0.1:8000/
Using the URLconf defined in mysite.urls, Django tried these URL patterns, in this order:
​
polls/
admin/
The empty path didn’t match any of these.
​
You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.
​

I tried to re-do the steps mentioned above (the first three steps of Part 4), making sure I use the correct paths, but I still get errors.

This is how my .py’s look:

…pollsviews.py :

from django.http import HttpResponseRedirect
from django.shortcuts import render, get_object_or_404
from django.urls import reverse

from .models import Choice, Question


def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    context = {'latest_question_list': latest_question_list}
    return render(request, 'polls/index.html', context)


def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})


def results(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/results.html', {'question': question})


def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        return render(request, 'polls/detail.html', {  # Redisplay the question voting form
            'question': question,
            'error_message': "You didn't select a choice"
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing with POST data.
        # This prevents data from being posted twice if a user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

JavaScript
 
from django.http import HttpResponseRedirect
from django.shortcuts import render, get_object_or_404
from django.urls import reverse
​
from .models import Choice, Question
​
​
def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]
    context = {'latest_question_list': latest_question_list}
    return render(request, 'polls/index.html', context)
​
​
def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})
​
​
def results(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/results.html', {'question': question})
​
​
def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        return render(request, 'polls/detail.html', {  # Redisplay the question voting form
            'question': question,
            'error_message': "You didn't select a choice"
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing with POST data.
        # This prevents data from being posted twice if a user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))
​

…/polls/urls.py:

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.index, name='index'),  # ex: /polls/
    path('<int:question_id>/', views.detail, name='detail'),  # ex: /polls/5/
    path('<int:question_id>/results/', views.results, name='results'),  # ex: /polls/5/results/
    path('<int:question_id>/vote/', views.vote, name='vote'),  # ex: /polls/5/vote/
]

JavaScript
 
from django.urls import path
​
from . import views
​
app_name = 'polls'
urlpatterns = [
    path('', views.index, name='index'),  # ex: /polls/
    path('<int:question_id>/', views.detail, name='detail'),  # ex: /polls/5/
    path('<int:question_id>/results/', views.results, name='results'),  # ex: /polls/5/results/
    path('<int:question_id>/vote/', views.vote, name='vote'),  # ex: /polls/5/vote/
]
​

I have already looked at these questions:

Page not found (404) Request Method: GET Request URL: http://127.0.0.1:8000/

How to fix “Page not found (404)” error (“Django tried these URL patterns… The empty path didn’t match any of these.”)

Page not found 404 on Django site?

Django Error: Page not found (404) Request Method: GET Request URL: http://127.0.0.1:8000/helpdesk/login/?next=/

How to fix “Page not found (404)” error (“Django tried these URL patterns… The empty path didn’t match any of these.”)

Django Http404 message not showing up

Django Page not found(404) error (Library not found)

Django 404 error-page not found

(and many more) trying to figure this out for two days, but I can’t seem to figure it out. I realize that this question probably is a duplicate, but I’m desperate, and I appreciate any help I can get.

Answer

So this isn’t a problem with any of your HTML files or the URLs file. The clue to that can be found in the error message, here: Raised by: polls.views.detail

Which indicates that detail returns a 404 object. If we look at that part of views, you have this line:

question = get_object_or_404(Question, pk=question_id)

My guess is that you don’t have a question in the database with the ID 1 OR the database is empty. If either of those are true, get_object_or_404 would return a 404.

If there was an issue with the page actually not being found, you would not see the “Raised by” part of the error at all.

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Answer