title: Updating values using Python user input
body: <p>I have a dataset where, whenever the date value in the 'Update' column is updated, the other
  columns will be updated as well. Logic is:</p>
  <pre><code>Date1 is 3 months from Date2
  Date2 is 1 month from Date3
  and Update is 1 month from Date3
  </code></pre>
  <p><strong>The only data that is changing is the dates, which are essentially getting shifted based upon the user input.</strong></p>
  <p><strong>Data</strong></p>
  <pre><code>Date1       Date2       Date3       Update
  1/1/2021    4/1/2021    5/1/2021    6/1/2021
  5           2           1           1
          
  </code></pre>
  <p><strong>Desired</strong></p>
  <p>Input prompt will ask user which date value they wish to input.
  User inputs the date '8/1/2021', which updates the remaining column date values.</p>
  <pre><code>Date1       Date2       Date3       Update
  3/1/2021    6/1/2021    7/1/2021    8/1/2021
  5           2           1           1
  </code></pre>
  <p><strong>Doing</strong></p>
  <p>I believe I can use a combination of a function as well as user prompt to approach this problem.</p>
  <pre><code>#take input
  datevalue = input(&quot;Enter date value: &quot;)
  print(datevalue)
  
  
  
  
  #use input variable in function or script to create date update
  s = df['Update'].str.replace(r'(\S+) (\S+)', r'\2\1')
  df['Update'] = (pd.PeriodIndex(s, freq='D') + 3).strftime('D%q %Y')
  </code></pre>
  <p>I am looking for <strong>some starting point suggestion or a good foundation/documentation</strong> on how to best approach this problem. I am still researching. Any suggestion is appreciated.</p>