import timeit
base = """
Is = []
for i in range(1000):
    I = C()
    I.a = 1; I.b = 2; I.c = 3; I.d = 4
    t = I.a + I.b + I.c + I.d
    Is.append(I)
"""

stmt = """
class C:
    __slots__ = ['a', 'b', 'c', 'd']
""" + base
print('Slots   =>', end=' ')
print(min(timeit.repeat(stmt, number=1000, repeat=5)))

stmt = """
class C:
    pass
""" + base
print('Nonslots=>', end=' ')
print(min(timeit.repeat(stmt, number=1000, repeat=5)))