इंस्टेंस बनाम क्लास एट्रिब्यूट

class Dog:
    legs = 4
print(Dog.legs)
print(Dog().legs)

class Dog:
    def __init__(self, name):
        self.name = name
d1 = Dog('Rex')
d2 = Dog('Buddy')
print(d1.name, d2.name)

class C:
    x = 10
c = C()
c.x = 99  # instance shadows class attr
print(c.x)  # 99
print(C.x)  # 10

class C:
    items = []
C.items.append(1)
print(C().items)  # [1] — shared!

class C:
    def __init__(self):
        self.items = []
c1 = C(); c2 = C()
c1.items.append(1)
print(c1.items, c2.items)

class Dog:
    legs = 4
    def __init__(self, name): self.name = name
d = Dog('Rex')
print(d.__dict__)
print(Dog.__dict__.keys())

class Date:
    def __init__(self, y, m, d): self.y,self.m,self.d=y,m,d
    @classmethod
    def from_string(cls, s):
        y,m,d=map(int,s.split('-'))
        return cls(y,m,d)
dt=Date.from_string('2024-01-15')
print(dt.y,dt.m,dt.d)

class MathUtils:
    @staticmethod
    def add(a, b): return a + b
print(MathUtils.add(3, 4))

class Widget:
    count = 0
    def __init__(self):
        Widget.count += 1
Widget(); Widget(); Widget()
print(Widget.count)

class P:
    def __init__(self, x): self.x = x
p = P(5)
print(hasattr(p, 'x'), hasattr(p, 'z'))
print(vars(p))