Python getters and setters

[MRAB]

On 17/08/2013 17:53, Fernando Saldanha wrote:
> I am new to Python.
>
> I understand that it is "unpythonic" to write getters and setters, and that property() can be used if necessary.
>
> This deals with the case of attributes, but there are other kinds of information available within a class.
>
> Suppose my class contains an attribute called "data" that can potentially provide a lot of information that will be needed by class users. I have two options:
>
> 1) For each piece of information within data (e.g., length) I write a method that retrieves that information:
>
>      def data_length(self):
>          return len(self.data)
>
> 2) I do not create such a method. Users that are interested in that information will have to write len(obj.data), where obj is a previously instantiated object of my class.
>
> Which one of the two alternatives fits better with the Python philosophy? The first alternative is more work for me, creates a "heavier" class and may have slower performance, but makes things easier for the user and is more implementation independent.
>
If the attribute is public, i.e. the user is expected to write obj.data, 
then
len(obj.data) is the right way to get its length.