[program-l] Re: Python: Please Help Me Think Out Loud About When To Make Classes And When Not To Make Them

  • From: Soronel Haetir <soronel.haetir@xxxxxxxxx>
  • To: program-l@xxxxxxxxxxxxx
  • Date: Tue, 30 Oct 2012 10:52:28 -0800

The main item I use when deciding to make classes or not is whether
there is persistent state that should travel with the function
call(s).  If there is no persistent state then I see no reason to make
a class.  It is also one of the things I don't care for about java and
.net (I'm aware that the .net framework itself can handle global
functions, but the languages I use with it cannot so it's pretty much
a waste of effort, and I find static classes a rather silly
substitute)

This factor is not particular to python, instead it extends to pretty
much every language I've used that gives the choice of whether to use
classes or not.

On 10/30/12, Homme, James <james.homme@xxxxxxxxxxxx> wrote:
> Hi,
> I think that my chess project is one in which it's OK to make the class that
> uses the cmd class, but is also OK to import a file that has chess related
> functions, but is not a class. If I'm wrong, please tell me. Here's how I
> view the project in my mind right now, and where it's going. But the big
> question in my mind is this. What makes you either decide to make classes or
> not make them?
>
> I now have a file that I'm going to change so that it returns the results of
> the functions it calls from my chess board module. In order to make the
> functions in my command file see the ones I'm making in the chess board
> file, I put an import statement at the top. When I did this, my functions
> could call the ones in my chess board file.
>
> I'm going to have functions like new game. I think that this makes it so
> that I don't need to instantiate a chess board class. I say this because of
> the way this whole thing is constructed. Every time
> I type a command, it gets ready to receive a new one.  I'm keeping the help
> functions in my commands file, though. I'm not going to migrate them over,
> or put functions in the chess board file that return help text. I may have
> to change my mind, but this is how I see it working right now.
>
> The only thing my commands file will do is start and run the command loop.
>
> I'm hoping that once I learn how to make GUI programs, I can simply swap out
> my command line processing file and make the GUI file just use the functions
> in the chess board file. So, in stead of a command loop, it would make some
> sort of event loop or whatever that GUI thing is called that waits for you
> to click stuff and choose stuff.
>
> So theoretically, I can put out a command line version of my program, and a
> GUI version of it.
>
> But what concerns me is the question of whether I'm constructing it this way
> because I come from a procedural programming back ground and subconsciously
> want to avoid making classes, or whether this is the best way to construct
> the project.
>
> It seems like a nice way to divide things up, though, so that it helps me
> think of each file having a set of functions. For example, maybe there would
> be a third file that does nothing but save and load game data from disk,
> assuming that I want to build in the capability to save and load games in
> progress, and I see no reason I wouldn't want to do that. Here again,
> though, I'm thinking that the chess board file would import the one that
> loads and saves the data. And I'm thinking that the file that does that may
> not need to contain a class that does this. I'm not that far in my thinking
> though.
>
> Thanks for listening.
>
> Jim
>
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-- 
Soronel Haetir
soronel.haetir@xxxxxxxxx
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