import json
from datetime import date

today = date(2025, 6, 9)

def handle(obj):
    if isinstance(obj, date):
        return obj.isoformat()
    raise TypeError("Not serializable")

print(json.dumps({"today": today}, default=handle))

def g(lst):
    return 0 if len(lst) == 0 else g(lst[1:]) - lst[0]
 
print(g([]))

class B:
    __y = 10

b = B()
print(b.__y)

class C:
    z = 5
    items = []

c1, c2 = C(), C()
c1.z = 8
c2.items.append('ok')
print(c1.z, len(c1.items))

class D:
    shared = {}

d1 = D()
d2 = D()

d1.shared['a'] = 1
d2.shared['b'] = 2

print(d1.shared)

class F:
    value = 7

f1 = F()
f2 = F()

del F.value
print(f2.value)

class H:
    level = 3

h = H()
h.level = 4

print(H.__dict__['level'], h.__dict__['level'])

class J:
    pass

j = J()
setattr(j, 'color', 'red')

print(j.color)

s = list(map(lambda x: x * x, (1, 2, 3, 4)))
print(s)