title: Some ways to combine sets in python
body: <p>I am trying to write a game that uses grids, and I need a way to make sets by combining two other sets.</p>
  
  <p>For example, if I had <code>[a, b, c]</code> and <code>[1, 2, 3]</code>, are there are any functions in Python 3 that will give me <code>[a1, a2, a3, b1, b2, b3, c1, c2, c3]</code>?</p>