How would I check if a letter was in a random word?

I am creating a game, and it entails picking a random word from a list, then asking the user for a letter input. I have this. I now need to check if the letter input is in the random word. How would I do this? I don't have Python on my computer so I can't check if my code works until tomorrow(this is a school project so to check my code I use the school computers). I'm not exactly sure where to start with this, so any guidance would be much appreciated, as I am fairly new to Python(as you may have guessed).