__new__

class A:
    def __new__(cls, *args, **kwargs):
        print ('new', cls, args, kwargs)
        return super().__new__(cls)
    def __init__(self, *args, **kwargs):
        print ('init', self, args, kwargs)

x = A()

__new__ allows you to modify immutable types before the object instance is created. __new__ occurs before __init__ so things like this are possible:

class Uppercase Tuple(tuple):
    def __new__(cls, iterable):
        upper_iterable = (s.upper() for s in iterable)
        return super().__new__(cls, upper_iterable)

Whereas this was not possible because the class object already exists even if the instance doesnt yet exist. the OBJECT is what we're trying to beat to the punch

class Uppercase Tuple(tuple):
    def __init__(self, iterable):
        print (f'init {iterable}')
        for i, arg in enumerate (iterable):
            self[i] = arg. upper()

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Backlinks

• __new__ Vs __init__ in Python (DevLog)