Django KeyError at forms.py

I'm learning django and I'm playing around with forms and registering users.
When I submit the registration form with the username, email, password, and confirm password fields filled, I get an error that states:

KeyError at director/register/
"confirm_password"

However, when I look at the POST data in the error message I clearly see the data I'm trying to access.

csrfmiddlewaretoken: blahblahblabh

username: dasdasd

email: dasd@dsada.com

password: test123!

confirm_password: test123!

Below are the forms.py, portion of the views.py, register.html files.

forms.py

from django import forms
from django.contrib.auth.forms import UserCreationForm, UserChangeForm
from .models import CustomUser
class CustomUserCreationForm(UserCreationForm):
class Meta:
model = CustomUser
fields = ("email", "password")
class CustomUserChangeForm(UserChangeForm):
class Meta:
model = CustomUser
fields = ("email", "password")
class RegisterUser(forms.Form):
username = forms.CharField(max_length=64, required=True)
email = forms.EmailField()
password = forms.CharField(max_length=128, widget=forms.PasswordInput(), required=True)
confirm_password = forms.CharField(max_length=128, widget=forms.PasswordInput(), required=True)
def clean_username(self):
username = self.cleaned_data["username"]
if CustomUser.objects.filter(username=username).exists():
raise forms.ValidationError("Email already exists")
return username
def clean_email(self):
email = self.cleaned_data['email']
if CustomUser.objects.filter(email=email).exists():
raise forms.ValidationError("Email already exists")
return email
def clean_password(self):
password = self.cleaned_data['password']
confirm_password = self.cleaned_data['confirm_password']
if password != confirm_password:
raise forms.ValidationError("Passwords do not match")
return password```

views.py (register_view)

def register_view (request):
if request.method == "POST":
form = RegisterUser(request.POST)
if form.is_valid():
new_user = form.save()
login(request, new_user)
return redirect('home')
else:
form = RegisterUser()
return render(request, 'pokedex/register.html', {'form': form})

register.html

{% extends 'pokedex/layout.html' %}
{% block title %}Register{% endblock title %}
{% block body %}
<h1>Register</h1>
{% if form.errors %}
<div class="alert alert-danger">
<ul>
{% for error in form.errors.values %}
<li>{{ error }}</li>
{% endfor %}
</ul>
</div>
{% endif %}
<form action="{% url 'register' %}" method="post">
{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Register">
</form>
{% endblock body %}

EDIT: Added Traceback

Environment:
Request Method: POST
Request URL: http://127.0.0.1:8000/pokedex/register/
Django Version: 4.1.7
Python Version: 3.9.2
Installed Applications:
['pokedex',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles']
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']
Traceback (most recent call last):
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\core\handlers\exception.py", line 56, in inner
response = get_response(request)
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\core\handlers\base.py", line 197, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:\Users\Alice\Documents\Code\stepchallenge\pokedex\views.py", line 45, in register_view
if form.is_valid():
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\forms\forms.py", line 205, in is_valid
return self.is_bound and not self.errors
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\forms\forms.py", line 200, in errors
self.full_clean()
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\forms\forms.py", line 437, in full_clean
self._clean_fields()
File "C:\Users\Alice\Documents\Code\env\lib\site-packages\django\forms\forms.py", line 452, in _clean_fields
value = getattr(self, "clean_%s" % name)()
File "C:\Users\Alice\Documents\Code\stepchallenge\pokedex\forms.py", line 38, in clean_password
confirm_password = self.cleaned_data['confirm_password']
Exception Type: KeyError at /pokedex/register/
Exception Value: 'confirm_password'

As described in the Django official documentation in the section Forms at Cleaning and validating fields that depend on each other, you cannot read self.cleaned_data['confirm_password'] inside the function clean_password, as the field might not be populated yet.

I suggest you to do the validation overriding the clean function like this:

class RegisterForm(forms.Form):
    username = forms.CharField(max_length=64, required=True)
    email = forms.EmailField()
    password = forms.CharField(max_length=128, widget=forms.PasswordInput(), required=True)
    confirm_password = forms.CharField(max_length=128, widget=forms.PasswordInput(), required=True)

    def clean_username(self):
        username = self.cleaned_data["username"]
        if CustomUser.objects.filter(username=username).exists():
            raise forms.ValidationError("Email already exists")
        return username
    
    def clean_email(self):
        email = self.cleaned_data['email']
        if CustomUser.objects.filter(email=email).exists():
            raise forms.ValidationError("Email already exists")
        return email
    
    # Removed clean_password function to use the default validation
    
    # Moved password check after all field are cleaned
    def clean(self):
        cleaned_data = super().clean()
        password = cleaned_data['password']
        confirm_password = cleaned_data['confirm_password']
        if password != confirm_password:
            raise forms.ValidationError("Passwords do not match")

I suggest also to take a look to Django official documentation - Forms as it describes how to avoid most errors.