title: Python: What is zip doing in this list comprehension
body: <p>I am trying to understand this:</p>
  
  <pre><code>a = "hello"
  b = "world"
  [chr(ord(x) ^ ord(y)) for (x, y) in zip(a[:len(b)], b)]
  </code></pre>
  
  <p>I understand the <code>XOR</code> part but I don't get what zip is doing.</p>