> > @area.setter > def area(self, value): > self._area = value > self._radius = self.area / (2 * math.pi) > > Uh oh... I'm in the middle of teaching Session 10 and couldn't figure out why my radius for a smaller area was bigger. Couldn't be. I did my algebra wrong, duh. Here's the debugged version:
# -*- coding: utf-8 -*- """ Created on Thu Oct 20 15:43:14 2016 @author: Kirby Urner toggle the import model_property on and off to see the example works the same either way. model_property contains a pure Python emulator of the built in property type. Related reading: https://mail.python.org/pipermail/edu-sig/2016-October/011548.html """ from model_property import Property as property import math class Circle: """setting either the radius or area attribute sets the other as a dependent value. Initialized with radius only, unit circle by default. """ def __init__(self, radius = 1): self.radius = radius @property def area(self): return self._area @property def radius(self): return self._radius @area.setter def area(self, value): self._area = value self._radius = math.sqrt(self._area / math.pi) #duh @radius.setter def radius(self, value): self._radius = value self._area = math.pi * (self._radius ** 2) def __repr__(self): return "Circle(radius = {})".format(self.radius) the_circle = Circle(5) print("the_circle:", the_circle) print("Area: ", the_circle.area) the_circle.area = 50 print("Radius when Area=50:", the_circle.radius)
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