Inspired by what I can only guess is my unsightly python version of greenbar, drewp has created a version with 100 percent more fun to look at. Thanks!
Drewp's version (see here) is what I always hoped greenbar would grow up to look like when it was written by someone who was not me. I wish the enumerate thing would work - I tried that originally too, but no, it's not to be. It works fine if the input is a regular file, but not when you want to read the stdout of another process. There's internal buffering in python that chunks up the input making the most common use of greenbar, watching a growing log file, hopeless.
Combining the two versions results in a super hybrid that works and is easy on your eyes. Tada!
pat = sys.argv
pat = None
lineno = 0
line = sys.stdin.readline()
if not line:
if (pat and pat in line) or (not pat and lineno % 2 == 0):
print "\x1b[7m%s\x1b[0m" % line.rstrip()
lineno = lineno + 1
P.s. The original awk version was shorter still. If I find a copy, I'll bury it so that python looks better.