forms.py

from django import forms
from django.forms.util import ValidationError
from django.contrib.auth.models import User

class RegistrationForm(forms.Form):
    first_name = forms.CharField(help_text = 'Your first name')
    email = forms. EmailField(help_text = 'Email id')
    username = forms.RegexField(regex = r'^\w+$', max_length = 30, help_text = 'Username must contain only alphabets / digits')
    password = forms.CharField(widget = forms.PasswordInput, help_text = 'Password must contain at least 6 characters', min_length = 6)
    confirm_password = forms.CharField(widget = forms.PasswordInput, help_text = 'Confirm Password', min_length = 6)
    
    def clean_username(self):
        data = self.cleaned_data
        try:
            user = User.objects.get(username = data['username'])
        except User.DoesNotExist:
            return data['username']
        raise forms.ValidationError(u'Username already exists')
    
    def clean_confirm_password(self):
        data = self.cleaned_data
        pass1 = data['password']
        pass2 = data['confirm_password']
        if pass1 and pass2:
            if pass1 != pass2: raise forms.ValidationError(u'Passwords do not match')
        return self.cleaned_data['confirm_password']