title: Find previous calendar day in python
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/441147/how-can-i-subtract-a-day-from-a-python-date">How can I subtract a day from a python date?</a>  </p>
  </blockquote>
  
  
  
  <p>I have a set of files that I'm saving by date, year_month_day.txt format.  I need to open the previous day's text file for some processing.  How do I find the previous day's date in python?</p>