Compare object sizes in python 3.6

test2.py

from pympler import asizeof

class Coordinates():
    def __init__(self, x, y):
        self.x = x
        self.y = y


class CoordinatesSlots():
    __slots__ = ('x', 'y')

    def __init__(self, x, y):
        self.x = x
        self.y = y

a = Coordinates(x=1, y=2)
b = CoordinatesSlots(x=1, y=2)

print('No slot: ', asizeof.asizeof(a))
print('With slot: ', asizeof.asizeof(b))

$ py test2.py
No slot:  344
With slot:  120