title: python3 ZipFile.extractall extracts a empty file
body: <p>Say I compress a <code>.txt</code> file as a <code>.zip</code> format with a password 123, the <code>.txt</code> file has a few characters like <code>abcd</code>. Then I make a new thread, using the <code>zipfile</code> lib in python3 to uncompress the <code>.zip</code> file. The core code in the thread is:</p>
  
  <pre><code>import zipfile as zf
  zipf = zf.ZipFile(target)
  zipf.extractall(path='./', pwd=password)
  </code></pre>
  
  <p>However, the <code>.txt</code> file extracted is empty, namely there is no character in it. Then I do the same experiment with a <code>.jpeg</code> image, this time, the image could be extracted perfectly.</p>
  
  <p>I am so confuse about this, could anyone propose a reasonable explanation ?</p>