为什么我会收到 AttributeError: 'NoneType' object has no attribute 'something'？

我收到一条错误消息：

AttributeError: 'NoneType' object has no attribute 'something'

我该如何理解这个消息？

哪些一般情况可能会导致这种情况AttributeError，以及如何识别问题？

_{This is a special case of AttributeErrors. It merits separate treatment because there are a lot of ways to get an unexpected None value from the code, so it's typically a different problem; for other AttributeErrors, the problem might just as easily be the attribute name.}

_{See also What is a None value? and What is a 'NoneType' object? for an understanding of None and its type, NoneType.}

NoneType 意味着您实际上拥有的不是您认为正在使用的任何类或对象的实例None。这通常意味着上面的赋值或函数调用失败或返回意外结果。