title: How do I check an input answer in python 3
body: <p>I am a beginner in Python. As a step to try and learn it
  I am now creating a story type game. </p>
  
  <p>So I want to check if the user has entered a valid input.</p>
  
  <pre><code>print("You see two roads, one to the left and one to the right...\n")
  time.sleep(1)
  answer = input("Do you want to go left or right?[Valid answer is yes/no\n").lower
  
  if answer == "yes" :
        print("You start to walk left")
  else:
        print("You end your journey here, thanks for playing")
        quit()
  </code></pre>
  
  <p>Ok, so basically the only check I get here is if the user types yes or no, but what if the user types something else? 
  I would then love to have an option that prints out "Please type yes or no" and then sends the user the same question again??</p>
  
  <p>Sorry if I did not manage to answer this in a good way, english is not my native language. </p>