title: python get unicode string size
body: <p>I have a binary file. This file contains an UTF-8 string. Moreover, it is guaranteed that this string is just a single word.
  In python, how can I get number of letters in this string?</p>
  
  <p>Let's say, I opened this file and read bytes:</p>
  
  <pre><code>bytes = open("1.dat", "rb").read()
  </code></pre>
  
  <p>What next have I to do to find out length (in letters, not bytes) of UTF-8 string?</p>