class Main:
    def __init__(self):
        self.number = 3

    def func(self):
        self.number = 4
        return self.number

    def __str__(self):
        self.number = 5
        return str(self.number)

if __name__ == '__main__':
    test = Main()
    print (test)

-> 5


class Main:
    def __init__(self):
        self.number = 3

    def func(self):
        self.number = 4
        return self.number

    def __str__(self):
        return str(self.number)

if __name__ == '__main__':
    test = Main()
    print (test)

-> 3

как получить 4 из функции func?