How do I attach a remote debugger to a Python process?

use Winpdb. It is a platform independent graphical GPL Python debugger with support for remote debugging over a network, multiple threads, namespace modification, embedded debugging, encrypted communication and is up to 20 times faster than pdb.

Features:

• GPL license. Winpdb is Free Software.
• Compatible with CPython 2.3 through 2.6 and Python 3000
• Compatible with wxPython 2.6 through 2.8
• Platform independent, and tested on Ubuntu Gutsy and Windows XP.
• User Interfaces: rpdb2 is console based, while winpdb requires wxPython 2.6 or later.

_{(source: winpdb.org)}

Well, you can get something quite similar to that using a twisted manhole, which works like this:

from twisted.internet import reactor
from twisted.cred import portal, checkers 
from twisted.conch import manhole, manhole_ssh 

def getManholeFactory(namespace):
    realm = manhole_ssh.TerminalRealm()
    def getManhole(_): 
        return manhole.Manhole(namespace) 
    realm.chainedProtocolFactory.protocolFactory = getManhole
    p = portal.Portal(realm)
    p.registerChecker(
        checkers.InMemoryUsernamePassword DatabaseDontUse(admin='foobar'))
    f = manhole_ssh.ConchFactory(p)
    return f

reactor.listenTCP(2222, getManholeFactory(globals()))
reactor.run() 

Then you just login to the program over ssh;

$ ssh admin@localhost -p 2222
admin@localhost's password: 

Using foobar as the password.

When you login you'll get a normal python prompt where you can just poke at the data. It's not quite the same as getting a traceback sent over to a host.

Now, this might be tricky to integrate to a GUI program, in that case you might need to choose another reactor, for instance for gtk based programs used the gtk2reactor etc.

If you want the actual traceback sent over you need to create a socket channel for both stderr, stdin and stdout which goes over the network instead of printing to your local host. Shouldn't be too hard to accomplish by using twisted.