I apologize for being nitpicky, but you shouldn't abuse the tuple assignment syntax. I had to expand out msum2 to be able to read it reasonably.
a = 0; b = (0, 0); c = float('infinity')
is preferable if a, b, and c are logically unrelated compared to a, b, c = 0, (0, 0), float('infinity')
especially as the list gets longer. Why should the reader first count to find where variable `foo' is on the left-hand side before then counting the same number of places on the right?bounds, s, t, j = (0,0), -float('infinity'), 0, 0
See the Python Style Guide: http://www.python.org/dev/peps/pep-0008/ "Compound statements (multiple statements on the same line) are generally discouraged."
There's also no reason to keep it on one line :-)
Newlines and equal signs are cheap; go wild!