Question

I’m looking for a clean, simple way to update class-level dictionaries, which are inherited from base classes. For example:

class Foo(object):
    adict = {'a' : 1}

class Bar(Foo):
    adict.update({'b' : 2})  # this errors out since it can't find adict

so that:

Foo.adict == {'a' : 1}
Bar.adict == {'a' : 1, 'b' : 2}

I’d prefer to not use instances here, and if possible not use class methods either.

Answer 1

Note that even if that worked, you’d update the same dictionary instead of creating a new one (so Foo.adict is Bar.adict and thus Foo.adict == Bar.adict).

In any case, the simplest way is to explicitly refer to the parent class’s dict (and copy it, see above):

class Bar(Foo):
    adict = dict(Foo.adict)
    adict.update({'b': 2})