تعدد الأشكال والطرق السحرية

class Dog:
    def speak(self):
        return "Woof!"

class Cat:
    def speak(self):
        return "Meow!"

class Duck:
    def speak(self):
        return "Quack!"

# تعدد الأشكال: بغض النظر عن الفئة، طالما لديها طريقة speak()
animals = [Dog(), Cat(), Duck()]
for animal in animals:
    print(animal.speak())

Woof!
Meow!
Quack!

class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height
    
    def area(self):
        return self.width * self.height

class Circle:
    def __init__(self, radius):
        self.radius = radius
    
    def area(self):
        return 3.14159 * self.radius ** 2

class Triangle:
    def __init__(self, base, height):
        self.base = base
        self.height = height
    
    def area(self):
        return 0.5 * self.base * self.height

# تعدد الأشكال — بغض النظر عن الشكل، فقط احسب المساحة
shapes = [Rectangle(3, 4), Circle(5), Triangle(6, 8)]
for shape in shapes:
    print(f"Area: {shape.area():.2f}")

Area: 12.00
Area: 78.54
Area: 24.00

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def __str__(self):
        """تمثيل نصي سهل للمستخدم"""
        return f"{self.name} ({self.age} years old)"
    
    def __repr__(self):
        """تمثيل نصي للمطور"""
        return f"Person('{self.name}', {self.age})"

p = Person("Zhang San", 25)
print(p)                    # Zhang San (25 years old) — يستدعي __str__
print(repr(p))              # Person('Zhang San', 25) — يستدعي __repr__

class Team:
    def __init__(self, members=None):
        self.members = members or []
    
    def add(self, member):
        self.members.append(member)
    
    def __len__(self):
        return len(self.members)
    
    def __str__(self):
        return f"Team({', '.join(self.members)})"

team = Team()
team.add("Zhang San")
team.add("Li Si")
team.add("Wang Wu")

print(len(team))            # 3 — يستدعي __len__
print(team)                 # Team(Zhang San, Li Si, Wang Wu)

class Playlist:
    def __init__(self):
        self.songs = []
    
    def add(self, song):
        self.songs.append(song)
    
    def __getitem__(self, index):
        return self.songs[index]
    
    def __len__(self):
        return len(self.songs)

playlist = Playlist()
playlist.add("Sunny Day")
playlist.add("Seven Li Fragrance")
playlist.add("Nocturne")

print(playlist[0])          # Sunny Day — يستدعي __getitem__
print(len(playlist))        # 3

# يدعم التقطيع والتكرار
for song in playlist:
    print(song, end=" ")    # Sunny Day Seven Li Fragrance Nocturne

class Demo:
    def __init__(self, value):      # المُنشئ
        self.value = value
    
    def __str__(self):              # str() / print()
        return str(self.value)
    
    def __repr__(self):             # repr() / تصحيح
        return f"Demo({self.value})"
    
    def __len__(self):              # len()
        return 1
    
    def __bool__(self):             # bool() / شرط if
        return self.value != 0
    
    def __eq__(self, other):        # ==
        return self.value == other.value
    
    def __lt__(self, other):        # < (للترتيب)
        return self.value < other.value
    
    def __add__(self, other):       # عامل +
        return Demo(self.value + other.value)
    
    def __getitem__(self, key):     # obj[key]
        return key

class Fraction:
    """فئة الكسر — تدعم الجمع"""
    def __init__(self, numerator, denominator=1):
        if denominator == 0:
            raise ValueError("Denominator cannot be zero")
        self.numerator = numerator
        self.denominator = denominator
    
    def __str__(self):
        if self.denominator == 1:
            return str(self.numerator)
        return f"{self.numerator}/{self.denominator}"
    
    def __add__(self, other):
        new_den = self.denominator * other.denominator
        new_num = self.numerator * other.denominator + other.numerator * self.denominator
        return Fraction(new_num, new_den)
    
    def __eq__(self, other):
        return (self.numerator * other.denominator) == (other.numerator * self.denominator)

f1 = Fraction(1, 3)
f2 = Fraction(1, 6)
print(f1)                           # 1/3
print(f1 + f2)                      # 9/18
print(Fraction(1, 2) == Fraction(2, 4))  # True

from dataclasses import dataclass

@dataclass
class Point:
    x: float
    y: float

@dataclass
class Student:
    name: str
    age: int
    score: float = 0.0    # قيمة افتراضية

# يحصل تلقائياً على __init__, __repr__, __eq__
p1 = Point(3.0, 4.0)
p2 = Point(3.0, 4.0)
print(p1)                   # Point(x=3.0, y=4.0)
print(p1 == p2)             # True (يقارن جميع الحقول تلقائياً)

s = Student("Zhang San", 20, 85.5)
print(s)                    # Student(name='Zhang San', age=20, score=85.5)