utils.py 文件源码

def __setattr__(self, name, value):
        """Mimic attr.s(frozen=True) behaviour but allow for attributes
        to be initialized after class instantiation.

        Useful when you would like a class to be immutable after a
        certain action, such as a save to a database.

        Any attributes created with ``attr.ib(init=False)`` or are
        initially set to ``None`` in ``__init__()`` are allowed to have
        their values be set once after initialization. Any other
        attributes with initial values set are immediately frozen upon
        initialization.

        **Note**: Obviously, this doesn't stop anyone from setting the
        uninitialized attributes before you've set it yourself.
        Hopefully, you've got responsibile users.

        Raises:
            :class:`attr.exceptions.FronzenInstanceError`: if a frozen
                attribute is set
        """
        current_value = getattr(self, name, None)
        if current_value is None or isinstance(current_value, attr.Attribute):
            super().__setattr__(name, value)
        else:
            raise attr.exceptions.FrozenInstanceError()