On Oct 3, 2:27 pm, George Sakkis <[EMAIL PROTECTED]> wrote:
> On Oct 3, 1:04 pm, Adam Lanier <[EMAIL PROTECTED]> wrote:
>
>
>
> > Relatively new to python development and I have a general question
> > regarding good class design.
>
> > Say I have a couple of classes:
>
> > Class Foo:
> > params = [ ]
> > __init__( self, param ):
> > ...
>
> > Class Bar:
> > data = None
> > __init__( self, data ):
> > ...
>
> > The class is going to be a wrapper around a list of Bars() (among other
> > things). I want the ability to pass to the constructor of Foo either:
> > a string 'baz'
> > a Bar object Bar( 'baz' )
> > a list of strings and/or bars ( 'baz', Bar( 'something else' ))
>
> > Am I going to have to use isinstance() to test the parameter to __init__
> > to see what type of data I'm passing in, i.e.,
>
> > Class Foo:
> > params = [ ]
> > __init__( self, param ):
> > if isinstance( param, list ):
> > for p in param:
> > addParam( p )
> > elif isinstance( param, str):
> > addParam( param )
>
> > addParam( self, param ):
> > if isinstance( param, Bar ):
> > self.params.add( param )
> > elif isinstance( param, str ):
> > self.params.add( Bar( param ))
> > else:
> > raise TypeError( "wrong type of input" )
>
> > Am I missing something here or is there a more Pythonic way to
> > accomplish this?
>
> I would use variable argument list for this; it's also consistent with
> your example Foo( 'baz', Bar( 'something else' )), otherwise you need
> to call it as Foo([ 'baz', Bar( 'something else' ) ])
>
> # always inherit from object unless you have a good reason not to
> class Foo(object):
>
> # XXX this is a class instance, shared by all Foo instances;
> # XXX probably not what you intended
> params = [ ]
>
> def __init__(self, *args):
> # uncomment the following line for instance-specific params
> # self.params = []
> for arg in args:
> if not isinstance(arg, Bar):
> # let the Bar constructor to do typechecking or whatnot
> arg = Bar(arg)
> self.params.add(arg)
>
> HTH,
> George
Or even better (Python 2.5):
class Foo(object):
def __init__(self, *args):
self.params = [arg if isinstance(arg, Bar) else Bar(arg) for
arg in args]
George
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