class A:
    x = 1

class B(A):
    pass

class C(A):
    pass

B.x = 2
A.x = 3

print(C.x)

data = [1, 2, 3]
data += [4, 5]
data = data[1:-1]
print(sum(data))

class Model:
    val = 1
    lst = [val for _ in range(3)]

print(Model.lst)

data = [1, 2, 3]
data += [4, 5]
data = data[1:-1]
print(sum(data))

class Model:
    val = 1
    lst = [val for _ in range(3)]

print(Model.lst)

class Model:
    val = 1
    lst = [val for _ in range(3)]

print(Model.lst)

def increment(x):
    x += 10
    return x

value = 5
new_value = increment(value)
print(value + new_value)

data = [5, 10, 15, 20]
data.extend([x // 2 for x in data[:2]])
print(sum(data))

class MetaClass(type):
    def __new__(cls, name, bases, dct):
        dct['meta_value'] = 100
        return super().__new__(cls, name, bases, dct)
    
    def __init__(cls, name, bases, dct):
        cls.meta_value += len(name)

class A(metaclass=MetaClass):
    pass

class B(metaclass=MetaClass):
    pass

print(A.meta_value + B.meta_value)

gen = (x for x in range(3))
print(list(gen), list(gen))