[Answer]-Is it OK to reuse Django URL patterns. If so, how?

It’s certainly fine to do this. You can pass extra kwargs by specifying them in a dictionary after the pattern:

(r'^a/foo/$', my_view, {'b': False}),
(r'^b/foo/$', my_view, {'b': True}),

Alternatively, you could capture the prefix itself as a kwarg and check that in the dispatch method.