[EMAIL PROTECTED] a écrit : > I am new to Python but come from a C++ background so I am trying to > connect the dots :) . I am really liking what I see so far but have > some nubee questions on what is considered good form. For one thing I > am used to class variables
I assume you mean "instance attributes". In Python, "class attributes" are attributes that belong to the class object itself, and are shared by all instances. >being accessable only through methods > instaed of directly refrenced from the object instence. C++ have "access restriction" on attributes, which default is "private". Also, C++ makes a strong distinction between fonctions and data. Python's object model is very different here: 1/ There's no language-inforced access restriction. Instead, there's a naming convention stating that names starting with an underscore are implementation detail - ie : not part of the public interface - and as such *should* not be accessed by client code. 2/ Since Python is 100% object, functions (and methods) are objects too - so there's no strong "member variable vs method" distinction : both are attributes. > From what I > have read it looks like when you access a class variable directly in > Python it has something in the background that works similar to a > getter of setter. That's not technically true. *But* since Python has support for computed attributes, it's quite easy to turn a raw attribute into a computed one without the client code noticing it. So from a conceptual POV, you can think of direct attribute acces as a computed attribute acces with implicit getter/setter... > Would you normally write methods to retrive and set your class > variables or just refrence them directly? Depends. Languages like C++ or Java not having support for computed attributes, the tradition is to have a "public methods==behaviour" / "private data==state" mindset. With Python's support for both computed attributes and functions as first class objects, thinks are quite differents. The best approach IMHO is to think in terms of "public interface vs implementation", and choose to use attribute or method syntax based on semantic - how it will be effectively implemented being an orthogonal concern. To make things short : if it's obviously an attribute (ie : person's name etc), start by making it a public attribute and access it directly. If and when you need to control access to this attribute (either to compute it or make it read-only or whatever), then turn it into a property (aka computed attribute). -- http://mail.python.org/mailman/listinfo/python-list
