The Python community or whoever wrote pdb.py is largely responsible
Richard Wolff worked on the pydb.py that is in ddd. He
also contributed a little to pdb.py. In email he relates:
.. there was no attempt to make the two systems congruent. I
haven't done any work on either for quite some time. I'm retired
now and it's more than just unlikely that I'll ever do anything more
on either. Which means that as far as ddd and pydb have anything to
do with me, you're more than welcome to do whatever you like.
This effort merges in changes that were in the ddd pydb.py but not in
pdb.py. In particular, display expressions.
The command interface is from GDB, and so much of the error messages
and some parts of the documentation too.
Coordination for putting this together is by Rocky Bernstein.