Python __new__ dundor 方法

Question

我有下面的代码，我理解__new__用于创建一个类的实例，__init__方法用于初始化对象的值.

__init__ 是否只在返回基类的实例时调用？

我想要的是返回另一个类 A 的实例。有没有办法让__init__配置A类的实例？

# Python program to
# demonstrate __new__ method
  
# class whose object
# is returned
class GeeksforGeeks(object):
    def __str__(self):
        return "GeeksforGeeks"
          
# class returning object
# of different class
class Geek(object):
    def __new__(cls):
        return GeeksforGeeks()
          
    def __init__(self):
        print("Inside init")
          
print(Geek())
Output:

GeeksforGeeks

Answer 1

如 docs 中所述:

If __new__() is invoked during object construction and it returns aninstance or subclass of cls, then the new instance’s __init__()method will be invoked like __init__(self[, ...]), where self isthe new instance and the remaining arguments are the same as werepassed to the object constructor.

If __new__() does not return an instance of cls, then the new instance’s __init__() method will not be invoked.

所以不，它不会被调用。您可以自己手动调用它。