title: How to find customers who made 2nd purchase within 30 days?
body: <p>I need your quick help. I want to find a list of customer_id's and first purchase_date for customers who have made their second purchase within 30 days of their first purchase.</p>
  <p>i.e. curstomer_id's 1,2,3 have made their 2nd purchase within 30 days.</p>
  <p>I need curstomer_id's 1,2,3 and their respective first purchase_date.</p>
  <p>I have more than 100k customer_id's.
  <a href="https://i.stack.imgur.com/83ADS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/83ADS.png" alt="enter image description here" /></a></p>
  <p>How I can achieve this in pandas?</p>