Modern Python Cookbook

How to do it...

We'll break this into two parts. First, the general overview of defining settable properties, then the details of how to track state changes:

1. Define a class with a meaningful name.

2. Provide hidden attributes. These will be exposed as properties:


        class Leg: 
        def __init__(self): 
            self._rate= rate 
            self._time= time 
            self._distance= distance. 

3. For each gettable property, provide a method to compute the property value. In many cases, these will parallel the hidden attributes:


        @property 
        def rate(self): 
            return self._rate 

4. For each settable property, provide a method to set the property value:


        @rate.setter 
        def rate(self, value): 
            self._rate = value 
            self._calculate('rate')
 

The setter method has a special property decorator ...