If the integer is 2013, then the maximum number would be 3.

How would I proceed to doing so?

max([int(c) for c in str(2013)])

First you convert the number to a string, this allows to look at every digit one by one, then you convert it into a list of single digits and look for the maximum.

Another solution is

max = -1for c in str(2013):i = int(c)if i > max:max = i