Daniel Nogradi wrote:
> I'm relatively new to object oriented programming, so get confused
> about its usage once in a while. Suppose there is a class Image that
> has a number of methods, rotate, open, verify, read, close, etc. Then
> to use this class my natural guess would be to have something like
>
> image = Image( )
> image.read( "myfile.jpg" )
> image.rotate( )
> image.close( )
>
> But now it turns out that the PIL module uses this as
>
> image = Image.open( "myfile.jpg" )
> image.verify( )
> image.rotate( )
> image.close( )
>
> Perhaps the real Image class of PIL doesn't have these methods
> exactly, but doesn't matter, my point is the way it works. Is it
> normal that instead of first creating an instance of a class, it
> starts right away with one its methods? I of course understand that
> the PIL people simply made a choice that their module works this way,
> period, but I'm just wondering if it wouldn't have been more "logical"
> to do it along the way of my first example.
>
> I guess it's just a matter of convention or how the programmer feels
> like, but there are no conventions of this type? Which would be more
> pythonic? Or I shouldn't worry and it's totally up to the developer?
If I were coding a class like that, I'd probably do it like this:
image = Image("myfile.jpg")
image.rotate()
image.close()
And, in addition, there would be an image.open() method. In the above,
__init__ just calls it on its own when the filename is specified.
(Though, of course, I'm not at all familiar with the PIL module; there
might be more stuff going on behind the scenes with the way they do it.)
-Kirk McDonald
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