Receving a NoReverseMatch error in Django with Python

Question

I am currently working on a tutorial in the "Python Crash course" Book.

The tutorial is about creating a "Learning Log" Webapp with Django. The idea of the app is to allow users to: 1. create "Topics" they have learned about 2. add "Entries" to those Topics, describing details they have learned specific to those topics

I am currently stuck at creating an Entry form and receive an Error, when I run http://127.0.0.1:8000/new_entry/1

NoReverseMatch at /new_entry/1
Reverse for 'topic' with arguments '('',)' not found. 1 pattern(s) tried: ['topics/(?P<topic_id>[0-9]+)/$']
Request Method: GET
Request URL:    http://127.0.0.1:8000/new_entry/1
Django Version: 3.0.5
Exception Type: NoReverseMatch
Exception Value:    
Reverse for 'topic' with arguments '('',)' not found. 1 pattern(s) tried: ['topics/(?P<topic_id>[0-9]+)/$']
Exception Location: C:\Users\DR\Desktop\learning_log\ll_env\lib\site-packages\django\urls\resolvers.py in _reverse_with_prefix, line 677
Python Executable:  C:\Users\DR\Desktop\learning_log\ll_env\Scripts\python.exe
Python Version: 3.8.2
Python Path:    
['C:\\Users\\DR\\Desktop\\learning_log',
 'C:\\Program '
 'Files\\WindowsApps\\PythonSoftwareFoundation.Python.3.8_3.8.752.0_x64__qbz5n2kfra8p0\\python38.zip',
 'C:\\Program '
 'Files\\WindowsApps\\PythonSoftwareFoundation.Python.3.8_3.8.752.0_x64__qbz5n2kfra8p0\\DLLs',
 'C:\\Program '
 'Files\\WindowsApps\\PythonSoftwareFoundation.Python.3.8_3.8.752.0_x64__qbz5n2kfra8p0\\lib',
 'C:\\Users\\DR\\AppData\\Local\\Microsoft\\WindowsApps\\PythonSoftwareFoundation.Python.3.8_qbz5n2kfra8p0',
 'C:\\Users\\DR\\Desktop\\learning_log\\ll_env',
 'C:\\Users\\DR\\Desktop\\learning_log\\ll_env\\lib\\site-packages']
Server time:    Wed, 15 Apr 2020 19:46:06 +0000

The forms.py file:

from django import forms

from .models import Topic, Entry

class TopicForm(forms.ModelForm):
    class Meta:
        model = Topic
        fields = ['text']
        labels = {'text': ''}

class EntryForm(forms.ModelForm):
    class Meta:
        model = Entry
        fields = ['text']
        labels = {'text': ''}
        widgets = {'text': forms.Textarea(attrs={'cols': 80})}

The urls.py file:

from django.urls import path
from . import views

app_name = "learning_logs"
urlpatterns = [
    # --snip--
    # Page for adding new entry
    path('new_entry/<int:topic_id>', views.new_entry, name='new_entry'),
]

And views.py:

from django.shortcuts import render, redirect

from .models import Topic
from .forms import TopicForm, EntryForm


#--snip
def new_entry(request, topic_id):
    """Add a new entry for a particular topic."""
    topic = Topic.objects.get(id=topic_id)

    if request.method != 'POST':
        # No data submitted; create a blank form.
        form = EntryForm()
    else:
        # POST data submitted; process data.
        form = EntryForm(data=request.POST)
        if form.is_valid():
            new_entry = form.save(commit=False)
            new_entry.topic = topic
            new_entry.save()
            return redirect('learning_logs:topic', topic_id=topic_id)

    # Display a blank or invalid form.
    context = {'topic': topic, 'form': form}
    return render(request, 'learning_logs/new_entry.html', context)

And finally the new_entry.html:

{% extends "learning_logs/base.html" %}

{% block content %}

    <p><a href="{% url 'learning_logs:topic' topic_id %}">{{ topic }}</a></p>

    <p>Add a new entry:</p>

    <form action="{% url 'learning_logs:new_entry' topic.id %}" method='post'>
        {% csrf_token %}
        {{ form.as_p }}
        <button name="submit">Add entry</button>
    </form>

{% endblock content %}

And topic.html:

{% extends "learning_logs/base.html" %}

{% block content %}

    <p>Topic: {{ topic }}</p>

    <p>Entries:</p>

    <p>
        <a href="{% url 'learning_logs:new_entry' topic.id %}">Add new entry</a>
    </p>

    <ul>
    {% for entry in entries %}
        <li>
            <p>{{ entry.date_added|date:'M d, Y H:i' }}</p>
            <p>{{ entry.text|linebreaks }}</p>
        </li>
    {% empty %}
        <li>There are no entries for this topic yet.</li>
    {% endfor %}
    </ul>

{% endblock content %}

Any help would be much appreciated!

Answer 1

The mistake was in new_entry.html:

It should read:

{% url 'learning_logs:topic' topic.id %}

and not:

{% url 'learning_logs:topic' topic_id %}

Thanks to Klaus for pointing me at the line!