Class design question

[Adam Lanier]

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?