def __init__(self, act, session, author):
self._session = session<EOL>self._author = author<EOL>self._type = ActType.from_str(act.attrs['<STR_LIT>'])<EOL>useless_tag = act.div.find('<STR_LIT:a>', class_='<STR_LIT>')<EOL>if useless_tag is not None:<EOL><INDENT>useless_tag.extract()<EOL><DEDENT>attribute = self._get_assemble_method(self.type)(act)<EOL>self._attr = attribute.__class__.__name__.lower()<EOL>setattr(self, self._attr, attribute)<EOL>self._time = datetime.fromtimestamp(int(act['<STR_LIT>']))<EOL>
创建用户动态类实例.

        :param bs4.element.Tag act: 表示用户动态的页面元素
        :param Session session: 使用的网络会话
        :param Author author: Activity 所属的用户对象
        :return: 用户动态对象
        :rtype: Activity

        :说明:
            根据Activity.type不同可以获取不同属性，具体请看 :class:`.ActType`