Best approach with dynamic classes using Python globals()

result = globals()[classname](param).html

if classname == 'Foo':
    result = Foo(param).html
elif classname == 'Bar':
    ...

class_lookup = {'Class1' : Class1, ... }
 ...
 result = class_lookup[className](param).html

class Namespace(object):
    class Class1(object):
        ...
    class Class2(object):
        ...
...
result = getattr(Namespace, className)(param).html

def register_subclasses(base):
    d={}
    for cls in base.__subclasses__():
        d[cls.__name__] = cls
        d.update(register_subclasses(cls))
    return d


class_lookup = register_subclasses(MyBaseClass)

dispatch = {'Foo': Foo, 'Bar': Bar, 'Bizbaz': Bizbaz}

class Foo:
    lookup = True
    def __init__(self, params):
        # and so on

class_lookup = zip([(c, globals()[c]) for c in dir() if hasattr(globals()[c], "lookup")])