Logic to find permutations of a string

Question

to print all possible combination of characters in a string

Answer 1

p (n,r) = n!/(n-r)!
is the formula for finding the no. of permutations

Answer 2

that was interesting, and I've searched for info. there is a function for this in Python's standard module 'itertools'.
look at my code: http://www.sololearn.com/app/sololearn/playground/ctmEhmAQOsfI/

in future, try finding some info by yourself first, it's a really great skill for a good programmer.