Python中__get__()方法解析：动态生成方法代码疑问

Hey there! Let's break down exactly what that line is doing—this ties into Python's descriptor protocol, which is one of those behind-the-scenes mechanics that's super important but easy to miss.

First, remember this key fact: regular functions in Python are non-data descriptors—they come with a built-in __get__ method. When you call method.__get__(self), you're explicitly binding the function method to your MethodGen instance (the self here). The result is a bound method object—this is the exact same type of object you get when you reference a normal instance method like my_instance.my_method.

What does a bound method actually do? #

A bound method automatically passes the instance (self) as the first argument when you call it. So if your dynamically generated method expects self as its first parameter, calling the bound version will handle that argument injection for you—just like how regular instance methods work when you call them normally.

Why this line matters in your MethodGen setup #

Since your class uses __getattr__ to dynamically generate methods on the fly, these two lines work together to make the system efficient and behave like regular methods:

1. method.__name__ = name makes sure the dynamically created method has the correct name (matching the attribute name you're generating it for). This is crucial for debugging, introspection, or any code that checks method names.
2. setattr(self, name, method.__get__(self)) does two critical things:
   • It creates a bound method that's tied directly to your current MethodGen instance.
   • It stores this bound method as an attribute on the instance itself. This acts as a cache—next time you access self.name, it'll pull the already-bound method from the instance's attributes instead of triggering __getattr__ to regenerate it from scratch.

Quick concrete example #

Suppose your dynamically generated method looks like this:

def dynamic_method(self):
    print(f"Called on instance: {self}")

When you run dynamic_method.__get__(my_methodgen_instance), you get a bound method. Calling that bound method is identical to running dynamic_method(my_methodgen_instance)—the self argument is automatically passed in for you.

By storing this bound method on the instance, you avoid redundant method generation and make subsequent attribute accesses faster.

内容的提问来源于stack exchange，提问作者arun raju