title: String input validation for a letter followed by a number
body: <p>I want the userinput to be in the format letter number. The letters should
  be from <code>A-H</code> and the numbers should be in between <code>1-7</code> For exampel <code>A4</code> or <code>H7</code>.
  I don't want the the userinput to be for example <code>AA</code>,<code>AAA</code>,<code>2B</code> or <code>22</code>.
  This is what I have done so far:</p>
  
  <pre><code>x=input("Write something:")
  
  if len(x) !=2:
      print("Wrong")
  
  letter=x[0]
  number= x[1]
  
  if number &gt;=8:
      print("Wrong")
  
  if letter not ["A","B","C","D","F","G"]:
      print("Wrong")
  
  if letter == int:
      print("Wrong")
  
  if number == str:
      print("Wrong")
  
  else:
      print("Perfect")
  </code></pre>