title: fast way to remove lowercase substrings from string?
body: <p>What's an efficient way in Python (plain or using numpy) to remove all lowercase substring from a string <code>s</code>? </p>
  
  <pre><code>s = "FOObarFOOObBAR"
  remove_lower(s) =&gt; "FOOFOOBAR"
  </code></pre>