title: Removing cells/rows that don't contain regex match with Python
body: <p>I have a csv of a single column containing supposedly phone numbers.  However, there are several cells containing the wrong number of digits, alphabet and symbols, etc.  I just want to keep every row whose cell contains exactly ten numerical digits and delete all other rows.</p>
  
  <p>I also have a file that includes a weird non-ascii character in the middle of every cell in the name column (after the first name).  Is there a simple way to discard every non-ascii character in a file?  I just want to get rid of it, though replacing it with a space would be fine, too.</p>
  
  <p>I already have pandas imported in the code I'm running on my csvs, so if that helps, it's available.</p>