title: listdir a directory and find if a file name that endswith ".mp4""
body: <p>Original question:</p>
  
  <pre><code>a = [1, 2, 3, 4, 5, 6, 4]
  
  print [True for i in a if i == 4]
  </code></pre>
  
  <p>result:</p>
  
  <pre><code>[True, True]
  </code></pre>
  
  <p>How do I code to break at first number 4?</p>
  
  <p>Following comments, edited to:</p>
  
  <p>I exactly want to listdir a directory with so many files. And find if a file endswith ".mp4".</p>