小编Zet*_*tor的帖子

{class foo(object):
    def __enter__ (self):
        print("Enter")
    def __exit__(self,type,value,traceback):
        print("Exit")
    def method(self):
        print("Method")
with foo() as instant:
    instant.method()}

执行此py文件,控制台显示以下消息:

Enter
Exit

instant.method()
AttributeError: 'NoneType' object has no attribute 'method'

无法找到方法？