What is happening when a python class is instantiated but it does not have any __init__() method defined?

Question

Given the following class declaration:

class FactorizationModel(ModelWrapper, Saveable, Loader):

in which ModelWrapper , Saveable , and Loader are other base classes of FactorizationModel

This class does not have any __init__ method defined. Instead it has a few def's including

def predict(self, user, product):

def predictAll(self, user_product):

def userFeatures(self):

def productFeatures(self):

Given there is no init method: please explain what is happening in the following invocation of a constructor.

From some client code that imports this class:

    return FactorizationModel(model)

Update OK the first answer here is correct. Adding relevant info to make this clear:

class ModelWrapper(object):
    # the following base class constructor is getting called implicitly..
    def __init__(self, model):
          ...

Answer 1

The initializer is inherited from a parent class, problem solved. It's sort of messed up in multiple inheritance, it will only use the first passed super class if there is a conflict. For example:

class C(A, B): # initializer from A will be used
class C(B, A): # initializer from B will be used

Answer 2

Python中的所有类都继承自一个名为Object的基类，该基类将该类分配到内存中（现在称为Object；一个类的实例。）因此，那些没有初始化程序的类将调用该基类初始化程序