class BooleanField(Field):    empty_strings_allowed = False    default_error_messages = {        ‘invalid‘: _(u"‘%s‘ value must be either True or False."),    }    description = _("Boolean (Either True or False)")    def __init__(self, *args, **kwargs):        kwargs[‘blank‘] = True        if ‘default‘ not in kwargs and not kwargs.get(‘null‘):            kwargs[‘default‘] = False        Field.__init__(self, *args, **kwargs)    def get_internal_type(self):        return "BooleanField"    def to_python(self, value):        if value in (True, False):            # if value is 1 or 0 than it‘s equal to True or False, but we want            # to return a true bool for semantic reasons.            return bool(value)        if value in (‘t‘, ‘True‘, ‘1‘):            return True        if value in (‘f‘, ‘False‘, ‘0‘):            return False        msg = self.error_messages[‘invalid‘] % str(value)        raise exceptions.ValidationError(msg)    def get_prep_lookup(self, lookup_type, value):        # Special-case handling for filters coming from a Web request (e.g. the        # admin interface). Only works for scalar values (not lists). If you‘re        # passing in a list, you might as well make things the right type when        # constructing the list.        if value in (‘1‘, ‘0‘):            value = bool(int(value))        return super(BooleanField, self).get_prep_lookup(lookup_type, value)    def get_prep_value(self, value):        if value is None:            return None        return bool(value)    def formfield(self, **kwargs):        # Unlike most fields, BooleanField figures out include_blank from        # self.null instead of self.blank.        if self.choices:            include_blank = (self.null or                             not (self.has_default() or ‘initial‘ in kwargs))            defaults = {‘choices‘: self.get_choices(                                       include_blank=include_blank)}        else:            defaults = {‘form_class‘: forms.BooleanField}        defaults.update(kwargs)        return super(BooleanField, self).formfield(**defaults)

 1     def to_python(self, value): 2         if value in (True, False): 3             # if value is 1 or 0 than it‘s equal to True or False, but we want 4             # to return a true bool for semantic reasons. 5             return bool(value) 6         if value in (‘t‘, ‘True‘, ‘1‘): 7             return True 8         if value in (‘f‘, ‘False‘, ‘0‘): 9             return False10         msg = self.error_messages[‘invalid‘] % str(value)11         raise exceptions.ValidationError(msg)

>>> a = True>>> b = False>>> c = 1>>> d = 0>>> e = 11>>> f = -1>>> a in (True,False)True>>> b in (True,False)True>>> c in (True,False)True>>> d in (True,False)True>>> e in (True,False)False>>> f in (True,False)False>>> 

>>> if 11:    print ‘aa‘    aa>>>