Django snippets

class SwithchedValueTypedChoiceField(MultipleChoiceField):
    """
    Return selected data as value instead of value html ttribute.
    """        
    def to_python(self, value):        
        if not value:
            return []
        elif not isinstance(value, (list, tuple)):
            raise ValidationError(self.error_messages['invalid_list'])
        
        def switched(value, choices):
            """
            Switched value generator
            """
            count = 0
            max_count = len(value)
            while count < max_count:
                yield choices[value[count]]
                count += 1

        value = list(switched(value, dict(self._choices)))
        return value
        
    def valid_value(self, value):
        "Check to see if the provided value is a valid choice"
        for k, v in self.choices:
            if isinstance(v, (list, tuple)):
                # This is an optgroup, so look inside the group for options
                for k2, v2 in v:
                    if value == smart_unicode(v2):
                        return True
            else:
                if value == smart_unicode(v):
                    return True
        return False