As a verb used when things are blending or being blended together, meld dates only to the first half of the 20th century. In its early days, the word attracted some unfavorable attention. Those who didn't like it tended to perceive it as a misuse of an older meld meaning "to declare or announce (a card or cards) for a score in a card game" (such as pinochle or gin rummy). But the more recent meld, a blend of melt and weld, was an entirely new coinage suggesting a smooth and thorough blending of two or more things into a single, homogeneous whole. The word is no longer controversial.
Hopefully, you're using a version control system like Git. If so, your comparison isn't between two different files but to find differences between the current working file and the one Git knows. Meld understands this, so if you run meld conway.py, where conway.py is known by Git, it'll show you any changes made since the last Git commit:
A caution about meld, I manage a number of CentOS 6 (yeah, we're going to 7 "real soon now") and my users like to use meld, but on a few occasions it's missed some diffs. Unfortunately, I'm usually too swamped to investigate. Perhaps a current version might not have that issue.
But, I still like meld for the nice graphical interface.
There's also tkdiff which comes with the tkcvs package.