Why do we nned both - __init__() and __new__()
Andrej Viktorovich <viktorovichandrej at gmail.com> writes:
> For my understanding both - __init__() and __new__() works like constructors. And __new__() looks is closer to constructor. __init__() is more for variable initialization. Why I can't just initialize in __init__() ?
> class ExampleClass(object):
> def __new__(cls,value):
> print("creating new instance with val %s" % (value,) )
> instance = super(ExampleClass,cls).__new__(cls)
> return instance
> def __init__(self, value):
> print("Initialising instance... with val %s" % (value,))
> self.payload = value
> exampleInstance = ExampleClass(42)
In this special case (as others already explained, it is quite common),
you do not need "__new__".
In the general case, constructing an object can be split into two
subtasks: obtain a raw piece of storage able to manage the object's state;
initialize the object's state. The first subtask is handled by "__new__",
the second by "__init__".
Python has defaults for both subtasks -- and as others already pointed
out, the default "__new__" is almost always sufficient.