I am no IPv6 expert, but this looks like a reasonable first approximation. The “http.server” module documentation should also be updated to say IPv6 addresses are supported on the command line, and I guess there should be a test case added.

But maybe see Lib/smtpd.py line 657 for how this is done in a more general way for the SMTP server module (Issue 14758), using getaddrinfo(). There is also Issue 20215 proposing to do something equivalent in the lower level “socketserver” module, which would probably make this change redundant.

It would also be nice for it to bind to both IPv4 and IPv6 if possible, but that is apparently not easy to do cross platform; see Issue 3213.