import re

from django.contrib.auth.models import User

from django.core.exceptions import ObjectDoesNotExist

from django import forms

class RegistrationForm(forms.Form):

username = forms.CharField(label='Username', max_length=30)

email = forms.EmailField(label='Email')

password1 = forms.CharField(label='Password',

widget=forms.PasswordInput())

password2 = forms.CharField(label='Password (Again)',

widget=forms.PasswordInput())

def clean_password2(self):

if 'password1' in self.cleaned_data:

password1 = self.cleaned_data['password1']

password2 = self.cleaned_data['password2']

if password1 == password2:

return password2

raise forms.ValidationError('Passwords do not match.')

def clean_username(self):

username = self.cleaned_data['username']

if not re.search(r'^\w+$', username):

raise forms.ValidationError('Username can only contain alphanumeric characters and the underscore.')

try:

User.objects.get(username=username)

except ObjectDoesNotExist:

return username

raise forms.ValidationError('Username already taken.')