title: pandas read_csv raises ValueError
body: <p>I want to read txt data seperated by ',' and '\t', and I use code below: </p>
  
  <p><code>io_df = pd.read_csv('input_output.txt',sep='\D|\t',engine = 'python')</code></p>
  
  <p>This triggered error information below:</p>
  
  <p><code>---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-38-5ab0138d93ac&gt; in &lt;module&gt;()
  ----&gt; 1 io_df = pd.read_csv('input_output.txt',sep='\D|\t',engine = 'python')</code></p>
  
  <p>How to solve this?</p>