title: Getting a substring out of a string raises a TypeError
body: <p>Update: The problem was caused by a typo, and therefore shouldn't be reproduced.</p>
  <p>I want to make a script which finds a number N which can be found in Pi starting from the N-th digit.</p>
  <p>Running this code (where pi is a string in the form &quot;31415926...&quot;):</p>
  <pre><code>for i in range(len(pi)):
    if i == pi[i-1,i+len(str(i))]:
      print(i)
  </code></pre>
  <p>Brings up this error: &quot;TypeError: string indices must be integers&quot;</p>