Add shape demonstration classes

lessons/python/shapes/circle.py

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+import numpy as np
+
+from .shape import Shape
+
+MANY_POINTS = 100
+
+
+class Circle(Shape):
+    def __init__(self, center: tuple = (1.0, 1.0), radius: float = 1.0) -> None:
+        self.c = center
+        self.r = radius
+        theta = np.linspace(0.0, 2 * np.pi, MANY_POINTS)
+        x = self.c[0] + self.r * np.cos(theta)
+        y = self.c[1] + self.r * np.sin(theta)
+        super().__init__(x, y)
+
+    def calculate_area(self) -> None:
+        self.area = np.pi * self.r**2

lessons/python/shapes/rectangle.py

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+import numpy as np
+
+from .shape import Shape
+
+
+class Rectangle(Shape):
+    def __init__(
+        self, lower_left: tuple = (1.0, 1.0), upper_right: tuple = (3.0, 2.0)
+    ) -> None:
+        self.ll = lower_left
+        self.ur = upper_right
+        x = [self.ll[0], self.ur[0], self.ur[0], self.ll[0]]
+        y = [self.ll[1], self.ll[1], self.ur[1], self.ur[1]]
+        super().__init__(x, y)
+
+    def calculate_area(self) -> None:
+        width = self.ur[0] - self.ll[0]
+        height = self.ur[1] - self.ll[1]
+        self.area = width * height

lessons/python/shapes/shape.py

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+from abc import ABC, abstractmethod
+
+import numpy as np
+
+
+class Shape(ABC):
+    @abstractmethod
+    def __init__(self, x: np.ndarray, y: np.ndarray) -> None:
+        self.x = x
+        self.y = y
+        self.n_sides = len(x)
+        self.area = None
+
+    @abstractmethod
+    def calculate_area(self) -> None:
+        ...

lessons/python/shapes/square.py

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+import numpy as np
+
+from .rectangle import Rectangle
+
+
+class Square(Rectangle):
+    def __init__(
+        self, lower_left: tuple = (1.0, 1.0), side_length: float = 2.0
+    ) -> None:
+        upper_right = (lower_left[0] + side_length, lower_left[1] + side_length)
+        super().__init__(lower_left, upper_right)