python 2.7 - Ways to set default value for class attribute without using hasattr -

i have set attribute class instance in case if doesn't exist. using code below achieve that:

class o(object):     pass  o = o() if not hasattr(o, 'some_attr'):     setattr(o, 'some_attr', none) print o.some_attr 

is there better way perform such action ?

classes , instances has own namespace represented pre-defined __dict__ attribute dictionary, method setdefault used instead of if hasattr -> setattr flow add new attribute class instance:

class o():     pass  o = o() o.__dict__.setdefault('some_attr', none)  print o.some_attr 

method sugggested @martijnpieters:

also access __dict__ attribute vars function , call setdefault method in code sample above:

vars(o).setdefault('some_attr', none) print o.some_attr