import pickle

filename = 'test'


class Test:
    def __new__(cls, arg):
        # do some stuff here
        return super().__new__(cls)
    def __init__(self, arg):
        self.arg = arg

x = Test(10)

with open(filename, 'wb') as fp:
    pickle.dump(x, fp)

with open(filename, 'rb') as fp:
    y = pickle.load(fp)