There's a solution to all of this: TAoCP has thought through these issues carefully, and it would probably be best to study the tradeoffs Knuth presented. Pyth

There's a solution to all of this: TAoCP has thought through these issues carefully, and it would probably be best to study the tradeoffs Knuth presented. Python handles common cases, but it breaks when you push it too far: >>> 1e100 1e+100 >>> 1e100+0.1 1e+100 >>> 1e100+0.1 == 1e100 True >>> 9007199254740992 + 0.5 9007199254740992.0 >>> 9007199254740992 + 0.5 == 9007199254740992 True >>> 9007199254740992 + 0.5 + 1 9007199254740992.0 >>> x = 9007199254740992 >>> y = x >>> y += 1 >>> x == y False >>> x = 9007199254740992 + 0.5 >>> y = x >>> x += 1 >>> x == y True You could argue that handling the common cases is all that's needed, but stuff like this pops up in e.g. writing software rasterizers. It might also be one reason why PyPy can't quite match the speed of native programs, though that's just a guess.