Magic Methods in Python

The so-called magic method, its official name is actually special method , which is an advanced syntax of Python that allows you to customize functions in classes and bind them to special methods of classes. For example, if you define __str__ () function in class A, when calling str (A ()), it will automatically call __str__ () function and return the corresponding result.

__new__ and __init__

First, let’s talk about __new__ and __init__ . These two methods allow you to change the behavior when creating an object from a class, and these two are also relatively easy to mix up. If you don't know the mechanics of the two methods themselves, you just need to remember, __new__ is the process of creating an object from a class. And __init__ is the process of initializing this object after having this object.

class A:
    def __new__(cls, *args, **kwargs):
        print("__new__")
        return super().__new__(cls, *args, **kwargs)

    def __init__(self):
        print("__init__")


if __name__ == '__main__':
    a = A()

The output is:

__new__
__init__

We can see that both __new__ and __init__ are used. We can roughly imagine:

obj = __new__(A)
__init__(obj)