def __setitem__(self, name, value):
        """Set the value of the named field. If there is 0 or multiple fields
        by that name, it is an error.

        Multiple checkboxes of the same name are special-cased; a list may be
        assigned to them to check the checkboxes whose value is present in the
        list (and uncheck all others).

        Setting the value of a ``<select>`` selects the given option (and
        confirms it is an option). Setting radio fields does the same.
        Checkboxes get boolean values. You cannot set hidden fields or buttons.

        Use ``.set()`` if there is any ambiguity and you must provide an index.
        """
        fields = self.fields.get(name)
        assert fields is not None, (
            "No field by the name %r found (fields: %s)"
            % (name, ', '.join(map(repr, self.fields.keys()))))
        all_checkboxes = all(isinstance(f, Checkbox) for f in fields)
        if all_checkboxes and isinstance(value, list):
            values = set(utils.stringify(v) for v in value)
            for f in fields:
                f.checked = f._value in values
        else:
            assert len(fields) == 1, (
                "Multiple fields match %r: %s"
                % (name, ', '.join(map(repr, fields))))
            fields[0].value = value

    def _get_value_for_text(self, text):
        for i, (option_value, checked, option_text) in enumerate(self.options):
            if option_text == utils.stringify(text):
                return option_value

        raise ValueError("Option with text %r not found (from %s)"
                         % (text, ', '.join(
                             [repr(t) for o, c, t in self.options])))

 def value__set(self, value):
     if self._forced_value is not NoValue:
         self._forced_value = NoValue
     for i, (option, checked) in enumerate(self.options):
         if option == utils.stringify(value):
             self.selectedIndex = i
             break
     else:
         raise ValueError("Option %r not found (from %s)" % (value, ", ".join([repr(o) for o, c in self.options])))

    def _get_value_for_texts(self, texts):
        str_texts = [utils.stringify(text) for text in texts]
        value = []
        for i, (option, checked, text) in enumerate(self.options):
            if text in str_texts:
                value.append(option)
                str_texts.remove(text)

        if str_texts:
            raise ValueError(
                "Option(s) %r not found (from %s)"
                % (', '.join(str_texts),
                   ', '.join([repr(t) for o, c, t in self.options])))

        return value

 def test_stringify_other(self):
     self.assertEquals(utils.stringify(123), "123")

 def test_stringify_binary(self):
     self.assertEquals(utils.stringify(b"foo"), "foo")

 def test_stringify_text(self):
     self.assertEquals(utils.stringify("foo"), "foo")