Several ways to "add two number strings"

I was presented with an anecdote from a guy doing software development job interviews that went like this: &#xA; Interviewer: Show me how you would add two big numbers represented as strings?&#xA; Candidate: How about `adder = lambda a,b: return int(a)+int(b)`?&#xA; Interviewer: No, the numbers are too big `int(a)` would fail.&#xA; Candidate: ...&#xA; First off, Python is a bit unique among modern…