Classes

Dave Angel davea at davea.name
Fri Oct 31 18:20:36 CET 2014


On 10/31/2014 12:31 PM, Seymore4Head wrote:

> In this class, we will follow the practice of accessing the contents
> of objects using methods known as getters and setters. While not
> required by Python, this practice encourages the user of the class to
> manipulates class objects solely via class methods. The advantage of
> following this practice is that the implementer of the class
> definition (often someone other than the user of the class) may
> restructure the organization of the data fields associated with the
> object while avoiding the need to rewrite code that uses the class.
>

Written by somebody who doesn't understand a fundamental point about 
Python. It's just not true that the user would have to rewrite code if 
the implementer change the members.

The Python way of writing getters and setters (if/when you get to that 
stage of a Python class) is through the property decorator or its 
equivalent.

class Pet():
     def __init__(self, ....):
         self.internal details set here

     @property()
     def age(self):
         return some_complicated_expression

And the user of the class fetches this by using

mypet = Pet(....)
hisage = mypet.age

No stupid parentheses needed.  When the class is first written, no work 
is needed.  When it's updated to multiply the internal age by 7, just 
write the function, and decorate it to look like a regular attribute.

More complicated things can be done.  But the point is that the user 
should just get the age, by accessing the age attribute, and if the 
implementation needs to change, it can change.

The time to make a class complicated, is when it needs to be.  And the 
user should not have to pay the price for "just in case."

-- 
DaveA



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