TutorialJan30.py

# Abstract Data Type
class PointT:
    def __init__(self, x, y):
        self.__point = (x, y)

    # sum : PointT -> R
    # sum is an instance method.
    # It acts on one instance.
    # In Python we call an instance an object.
    # An object from the class PointT is an object
    #    of type PointT.
    #  p : PointT
    def sum(self):
        # self.__point is the state variable 'point'.
        return self.__point[0] + self.__point[1]

p = PointT(1, 1)
q = PointT(2, 2)
print('p sum:', p.sum()) # 1 + 1 = 2
print('q sum:', q.sum()) # 2 + 2 = 4


# Abstract Object
# You might here "singleton"
class Data:
    Points = []

    def __init__(self):
        return None

    # "staticmethod" is called in Python "decorator"
    # You can recognize by its @
    @staticmethod
    def first_sum():
        return Data.Points[0].sum()

# NOT GOING TO DO THIS:
#d = Data()
#another_d = Data()

Data.S = [p, q]

d = Data()
d.x = 4
print(d.x)