title: Use of findall and parenthesis in Python
body: <p>I need to extract all letters <em>after</em> the <code>+</code> sign or at the beginning of a string like this:</p>
  
  <pre><code>formula = "X+BC+DAF"
  </code></pre>
  
  <p>I tried so, and I do not want to see the <code>+</code> sign in the result. I wish see only <code>['X', 'B', 'D']</code>.</p>
  
  <pre><code>&gt;&gt;&gt; re.findall("^[A-Z]|[+][A-Z]", formula)
  ['X', '+B', '+D']
  </code></pre>
  
  <p>When I grouped with parenthesis, I got this strange result:</p>
  
  <pre><code>re.findall("^([A-Z])|[+]([A-Z])", formula)
  [('X', ''), ('', 'B'), ('', 'D')]
  </code></pre>
  
  <p>Why it created tuples when I try to group ? How to write the regexp directly such that it returns <code>['X', 'B', 'D']</code> ?</p>