added example of function vs. oop

python_3_oop/chapter05/polygon.py

@@ -0,0 +1,51 @@
+import math
+
+
+# version with 2 separate functions
+
+def distance(p1, p2):
+    return math.sqrt((p1[0] - p2[0]) ** 2 + (p1[1] - p2[1]) ** 2)
+
+def perimeter(polygon):
+    perimeter = 0
+    points = polygon + [polygon[0]]
+    for i in range(len(polygon)):
+        perimeter += distance(points[i], points[i + 1])
+    return perimeter
+
+
+# oop version with classes
+
+class Point:
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def distance(self, p2):
+        return math.sqrt((self.x - p2.x) ** 2 + (self.y - p2.y) ** 2)
+
+
+class Polygon:
+
+    def __init__(self, points = []):
+        self.vertices = []
+        for point in points:
+            if isinstance(point, tuple):
+                # *point splits point into 2 parameters for Point.__init__()
+                point = Point(*point)
+            self.vertices.append(point)
+
+    def add_point(self, point):
+        self.vertices.append((point))
+
+    def perimeter(self):
+        perimeter = 0
+        try:
+            points = self.vertices + [self.vertices[0]]
+        except IndexError:
+            print("The polygon has no points.")
+        else:
+            for i in range(len(self.vertices)):
+                perimeter += points[i].distance(points[i + 1])
+            return perimeter