--foo-bar-baz is stored as foo_bar-baz and not foo_bar_baz

[maxtaco]

For hyphenated argument names, only the first hyphen is converted to an underscore, not all of them.

[hpaulj]

I wonder why this replacement is not done on positional dest. It's not done in the python code, where in some ways it matters more.

In the javascript Namespace, if you can't use ns.foo-bar-baz you can still use ns['foo-bar-baz']. But with the python Namespace you have to use getattr(ns, 'foo-bar-baz').

Maybe this needs an issue report in both versions.