title: Comparing two strings and returning the difference. Python 3
body: <p>My goal is to write a program which compares two strings and displays the difference between the first two non-matching characters.</p>
  
  <p>example: </p>
  
  <pre><code>str1 = 'dog'
  str2 = 'doc'
  </code></pre>
  
  <p>should return <code>'gc'</code></p>
  
  <p>I know that the code which I have tried to use is bad but I am hoping to receive some tips. Here is my poor attempt to solve the exercise which leads me to nowhere:</p>
  
  <pre><code># firstly I had tried to split the strings into separate letters
  str1 = input("Enter first string:").split()
  str2 = input("Enter second string:").split()
  
  # then creating a new variable to store the result after  comparing the strings
  result = ''
  
  # after that trying to compare the strings using a for loop
  for letter in str1:
      for letter in str2:
          if letter(str1) != letter(str2):
              result = result + letter
              print (result)
  </code></pre>