Patching methods

One thing to understand about decorators for classes is how to define “methods” outside classes and then how to plug them so everything works together.

To fully understand how methods work, you’ll want to learn about descriptors. But you don’t have to learn about descriptors to learn the gist of it.

Methods are “just” functions that are tied to classes, and “tied to” doesn’t mean they’re defined inside the class when the class is defined. “Tied to” just means they’re accessed as if they’re attributes from the class:

class Cls:
    def fn(self):
        pass

print(Cls.fn)  # <function Cls.fn at 0x103505430>
print(type(Cls.fn))  # <class 'function'>

This is exactly the same as if you define the class Cls and the function fn separately, and then assign the function fn to Cls.fn:

class Cls:
    pass

def fn(self):
    pass

Cls.fn = fn
print(Cls.fn)  # <function Cls.fn at 0x103505430>
print(type(Cls.fn))  # <class 'function'>