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
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