title: TypeError: string indices must be integers..what is the problem
body: <p>i'm getting TypeError: string indices must be integers... how can i solve this?
  And the code is:</p>
  
  <pre><code>def myfunc(x):
      y=''
      for i in x:
          y=y+x[i].upper() +x[i+1]
          i+=2
  
      return y
  </code></pre>