title: How to write Combination and Permutation from 2 numbers n and k in Ruby/Python?
body: <p>For example, if I have 100 distinguishable dogs and I want to randomly pick 3 of them. With a pocket-size calculator, I would do 100C3 or something similar. How can I do this in Ruby and Python?</p>
  <p>Edition 1: My questions were solved from Razvans and Riccardo Bucco solutions. (I flipped a fair coin once to decide to whom I give a check mark and to whom I give an upvote).</p>
  <p>Thank you, everyone.</p>