circle: added comments related to TH's solution; removed calls to self._radius that bypass setter call.

circle/circle.py

@@ -2,6 +2,7 @@ from math import pi
 
 
 class Circle:
+    # Missing docstring
     def __init__(self, radius=1):
         self.radius = radius
 
@@ -20,18 +21,19 @@ class Circle:
 
     @property
     def diameter(self):
-        return 2 * self._radius
+        return 2 * self.radius
 
     @diameter.setter
     def diameter(self, diameter):
         if diameter < 0:
             raise ValueError("Diameter cannot be negative")
-        self._radius = diameter / 2
+        self.radius = diameter / 2
 
     @property
     def area(self):
-        return pi * self._radius ** 2
+        return pi * self.radius ** 2
 
     @area.setter
     def area(self, area):
+        # Not required: property without setter will raise AttributeError when set
         raise AttributeError("Can't set attribute")