I don't think this should go in in this form.  What he says; plus: why should we support pickling compiled regular expressions when the uncompiled form is so much more portable?

There's maybe another way: sre can import copy_reg and make the registration request.

Rejected at the request of the author.
(Not deleted because the discussion is still valuable.)

Agreed, pickling of REs seems of marginal importance.
I'd have no problem with just dropping the ability, and seeing if anyone complains.  

I'm not entirely happy about having to import SRE
everytime someone wants to use pickle, but I cannot
come up with a better way to do this.

maybe we should drop pickle support?  we don't support
pickling of other code objects, after all...

my original comment was a bit unclear; the code pickles the source pattern (and the flags), and it recompiles the pattern when the pickle is unpacked.

but I think Andrew is right; let's drop this for now, and see if anyone misses it.

now, how do I *remove* a patch?

Implemented Guido's idea: the 'sre' module installs the pickler when it's first imported.  This means that you have to explicitly import 'sre' before you can unpickle a pattern.