title: Add multiple extensions in one filetypes mac - tkinter/filedialog/askopenfilename
body: <p>I am trying to use <code>tkinter.filedialog</code> to choose the file in Mac.</p>
  <p>It works fine with one filetype in this way:</p>
  <pre><code>filedialog.askopenfilename(filetypes=[(&quot;Excel files&quot;, &quot;*.xlsx&quot;)])
  </code></pre>
  <p>However, I want to choose either <code>xlsx</code> or <code>xls</code> files. I searched and found a question <a href="https://stackoverflow.com/questions/9239514/filedialog-tkinter-and-opening-files">filedialog, tkinter and opening files</a>. I use the similar way but it does not work with Mac if I change to this:</p>
  <pre><code>filedialog.askopenfilename(filetypes=[(&quot;Excel files&quot;, &quot;*.xlsx; *.xls&quot;)])
  </code></pre>
  <p>How should I change to choose either <code>xlsx</code> or <code>xls</code> files in the file dialog?</p>