class SecureString(str):
    MASKED = '*****'

    @classmethod
    def __masked__(cls, *args, **kwargs):
        return SecureString.MASKED

    def __repr__(self):
        return SecureString.__masked__()

    def __str__(self):
        return SecureString.__masked__()

    def __getitem__(self, item):
        if isinstance(item, slice):  # detect slicing
            return SecureString.__masked__()

    def __getattribute__(self, item):
        if 'get' == item:  # Return normal string
            return super(SecureString, self).__str__
        else:  # Return masked string
            return SecureString.__masked__

password = SecureString('abc')

# good
print('\n>>> positive')
print(password.get())
print(password.get().lower())

# bad
print('\n>>> negative')
print(password)
print(password.lower())
print(password.upper())
print(repr(password))
print(str(password))
print(password[::-1])