Продвинутое ООП: специальные методы, свойства и MRO

class Money:
    def __init__(self, amount, currency='AZN'):
        self.amount = amount
        self.currency = currency

    def __repr__(self):
        return f'Money({self.amount!r}, {self.currency!r})'

    def __str__(self):
        return f'{self.amount:.2f} {self.currency}'

price = Money(12.5)
print(price)
print(repr(price))
print([price, Money(3, 'USD')])
print(f'{price} | {price!r}')

from functools import total_ordering

@total_ordering
class Money:
    def __init__(self, amount, currency='AZN'):
        self.amount, self.currency = amount, currency

    def __eq__(self, other):
        if not isinstance(other, Money):
            return NotImplemented
        return (self.amount, self.currency) == (other.amount, other.currency)

    def __lt__(self, other):
        if not isinstance(other, Money) or other.currency != self.currency:
            return NotImplemented
        return self.amount < other.amount

    def __hash__(self):
        return hash((self.amount, self.currency))

prices = [Money(5), Money(2.5), Money(10)]
print([m.amount for m in sorted(prices)])
print(Money(5) == Money(5), Money(5) >= Money(2.5), Money(5) == 5)
print(len({Money(1), Money(1)}))

class Vector:
    def __init__(self, x, y):
        self.x, self.y = x, y

    def __repr__(self):
        return f'Vector({self.x}, {self.y})'

    def __add__(self, other):
        return Vector(self.x + other.x, self.y + other.y)

    def __mul__(self, k):
        return Vector(self.x * k, self.y * k)

    __rmul__ = __mul__

    def __abs__(self):
        return (self.x ** 2 + self.y ** 2) ** 0.5

    def __bool__(self):
        return bool(self.x or self.y)

v = Vector(3, 4)
print(v + Vector(1, 1), v * 2, 2 * v)
print(abs(v), bool(Vector(0, 0)))

class Playlist:
    def __init__(self, *songs):
        self._songs = list(songs)

    def __len__(self):
        return len(self._songs)

    def __getitem__(self, index):
        return self._songs[index]

    def __contains__(self, song):
        return song.lower() in (s.lower() for s in self._songs)

p = Playlist('Morning', 'Rain', 'Finale')
print(len(p), p[0], p[-1], p[1:])
print('rain' in p)
for song in p:
    print('>', song)

class Temperature:
    def __init__(self, celsius):
        self.celsius = celsius

    @property
    def celsius(self):
        return self._celsius

    @celsius.setter
    def celsius(self, value):
        if value < -273.15:
            raise ValueError('below absolute zero')
        self._celsius = value

    @property
    def fahrenheit(self):
        return self._celsius * 9 / 5 + 32

t = Temperature(25)
print(t.celsius, t.fahrenheit)
try:
    t.celsius = -300
except ValueError as e:
    print('error:', e)

class Student:
    count = 0

    def __init__(self, name, grade):
        self.name, self.grade = name, grade
        Student.count += 1

    @classmethod
    def from_csv(cls, line):
        name, grade = line.split(',')
        return cls(name, int(grade))

    @staticmethod
    def is_valid_grade(grade):
        return 1 <= grade <= 11

    def __repr__(self):
        return f'{type(self).__name__}({self.name!r}, {self.grade})'

class Graduate(Student):
    pass

print(Student.from_csv('Aysel,9'), Graduate.from_csv('Murad,11'))
print(Student.count, Student.is_valid_grade(12))

class Base:
    def save(self):
        print('Base.save')

class Logged(Base):
    def save(self):
        print('Logged: before')
        super().save()

class Validated(Base):
    def save(self):
        print('Validated: checking')
        super().save()

class Order(Logged, Validated):
    pass

print([c.__name__ for c in Order.__mro__])
Order().save()

from abc import ABC, abstractmethod

class Shape(ABC):
    @abstractmethod
    def area(self): ...

    def describe(self):
        return f'{type(self).__name__} with area {self.area():.2f}'

class Rect(Shape):
    def __init__(self, w, h):
        self.w, self.h = w, h

    def area(self):
        return self.w * self.h

print(Rect(3, 4.5).describe())
try:
    Shape()
except TypeError as e:
    print(e)

class Money:
    def __init__(self, amount):
        self.amount = amount

    def __repr__(self):
        return f'Money({self.amount})'

    # add __add__, __radd__ and __eq__ here

wallet = [Money(5), Money(10), Money(2)]
print(Money(1) + Money(2))
print(sum(wallet))
print(sum(wallet) == Money(17))

class Stack:
    def __init__(self):
        self._items = []

    def push(self, item):
        self._items.append(item)

    def pop(self):
        return self._items.pop()

    # add __len__ and __repr__ here

s = Stack()
print(bool(s))
s.push('a')
s.push('b')
print(s, len(s), bool(s))
print(s.pop(), s)