The same thing you'd do yoursef if you wanted to assign it to a namesake local variable even if it was in a dict to begin with: you'd make the dash an underscore.
It would be extremely unlikely that you would replicate the name as a local variable if it was in a dict, but regardless a dict doesn't have that limitation. The namespace thing is atrocious and bad design -- no straightforward way to iterate over them, merging/updating them is awful, collides with keyword methods (keys, items, etc.), and so on; thankfully more modern argument parsing libraries didn't repeat this mistake. It's just a shame this ended up in the standard library, but then Python standard library has never really been any good, e.g. logging and urllib1234567.
It would be extremely unlikely that you would replicate the name as a local variable if it was in a dict, but regardless a dict doesn't have that limitation. The namespace thing is atrocious and bad design -- no straightforward way to iterate over them, merging/updating them is awful, collides with keyword methods (keys, items, etc.), and so on; thankfully more modern argument parsing libraries didn't repeat this mistake. It's just a shame this ended up in the standard library, but then Python standard library has never really been any good, e.g. logging and urllib1234567.