I guess the slow bit is the DNS propagation? It is slow, yes -- but it makes some kind of sense. Basically, there can be loads of machines around the world caching DNS settings -- that's why it's fast enough to be usable :-)
One thing you can do to make it faster next time you make a change is modify the "TTL" value. That's the "Time to Live", a number in seconds that tells caching DNS servers how long they should cache before they get the server's details again. A lower TTL means that changes propagate faster -- but it does mean that access to your site can be marginally slower, because (of course) stuff isn't cached so much.
A useful tool to track DNS propagation is What's my DNS. You enter the hostname into the first input, then select the record type from the second (you'll probably want "CNAME" for a PythonAnywhere web app) then hit the "Search" button, and it'll tell you what values it gets from a bunch of locations around the world.
[edit] We've found 300 seconds to be a good TTL value.