dunder.py

class Stick:
    def __init__(self, color, length, weight):
        self.color = color
        self.length = length
        self.weight = weight


stick = Stick('yellow', 1, 0.324)


class Stick:
    def __init__(self, color, length, weight):
        self.color = color
        self.length = length
        self.weight = weight

    def __repr__(self):
        return f'Stick({self.color!r}, {self.length}, {self.weight})'

    def __str__(self):
        return f'{self.color} stick'


stick = Stick('yellow', 1, 0.324)

print(str(stick))
# yellow stick
print(f'I have a {stick}')
# I have a yellow stick
print(repr(stick))
# Stick('yellow', 1, 0.324)


class Stick:
    def __init__(self, color, length, weight):
        self.color = color
        self.length = length
        self.weight = weight

    def __eq__(self, other):
        return (self.color, self.length, self.weight) == (other.color, other.length, other.weight)

    def __ne__(self, other):
        return not self.__eq__(other)

    def __lt__(self, other):
        return self.length < other.length

    def __le__(self, other):
        return self.length <= other.length

    def __gt__(self, other):
        return self.length < other.length

    def __ge__(self, other):
        return self.length <= other.length

    def __add__(self, other):
        return Stick(f'{self.color}/{other.color}', self.length + other.length, self.weight + other.weight)

    def __repr__(self):
        return f'Stick({self.color!r}, {self.length}, {self.weight})'


stick1 = Stick('yellow', 1, 0.324)
stick2 = Stick('yellow', 1, 0.324)
stick3 = Stick('blue', 0.75, 0.454)

print(stick1 == stick2)
# True
print(stick1 == stick3)
# False
print(stick1 > stick3)
# False
print(sorted([stick2, stick3, stick1]))
# [Stick('blue', 0.75, 0.454), Stick('yellow', 1, 0.324), Stick('yellow', 1, 0.324)]
print(stick1 + stick2 + stick3)
# Stick('yellow/yellow/blue', 2.75, 1.102)


class Stick:
    def __init__(self, color, length, weight):
        self.color = color
        self.length = length
        self.weight = weight

    def __call__(self, *args, **kwargs):
        print('Spank, spank, spank, ...')


stick1 = Stick('yellow', 1, 0.324)
stick1()
# Spank, spank, spank, ...


class FirstNOddNumbers:
    def __init__(self, n):
        self.n = n
        self.count = 0
        self.number = 1

    def __iter__(self):
        return self

    def __next__(self):
        if self.count < self.n:
            cur, self.number = self.number, self.number + 2
            self.count += 1
            return cur
        raise StopIteration()


class Stick:
    def __init__(self, color, length, weight):
        self.color = color
        self.length = length
        self.weight = weight

    def __getitem__(self, item):
        return getattr(self, item)

    def __setitem__(self, key, value):
        setattr(self, key, value)


stick1 = Stick('yellow', 1, 0.324)
stick1['color'] = 'green'
print(stick1['color'])
# green