gistfile1.py

# a URL field that supports webcal:// links for Django
#
from django.forms.fields import URLField, URL_VALIDATOR_USER_AGENT, RegexField

import re

url_re = re.compile(
    r'^(https?|webcal)://' # http:// or https://
    r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+[A-Z]{2,6}\.?|' #domain...
    r'localhost|' #localhost...
    r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' # ...or ip
    r'(?::\d+)?' # optional port
    r'(?:/?|/\S+)$', re.IGNORECASE)
    
class URLWebCalField(URLField):
    def __init__(self, max_length=None, min_length=None, verify_exists=False,
            validator_user_agent=URL_VALIDATOR_USER_AGENT, *args, **kwargs):
        RegexField.__init__(self, url_re, max_length, min_length, 
                                                *args, **kwargs)
        self.verify_exists = verify_exists
        self.user_agent = validator_user_agent