在Python中，return self的作用为： Returning self from a method simply means that your method returns a reference to the instance object on which it was called. This can sometimes be seen in use with object oriented APIs that are des
在Python中，return self的作用为：
Returning self from a method simply means that your method returns a reference to the instance object on which it was called. This can sometimes be seen in use with object oriented APIs that are designed as a fluent interface that encourages method cascading.
链式调用