Python if else conditions when date gets changed

Question

I have a python code in which I need to compare entered date with existing pandas Date column and get index number of that rows. But if that date doesn't exist then it should get index number of rows of exact previous dates. Example of code and dataframe is given below.

Dataframe:-

 SR.No     Date
  1      01-12-2013
  1      01-12-2014
  1      01-12-2015
  1      01-12-2016
  1      01-12-2017 
  1      01-12-2018
  1      01-12-2019
  1      01-12-2020 
  1      01-12-2013
  1      01-12-2014
  1      01-12-2015
  1      01-12-2016
  1      01-12-2017 
  1      01-12-2018
  1      01-12-2019
  1      01-12-2020 
  2      01-12-2013
  2      01-12-2014
  2      01-12-2015
  2      01-12-2016
  2      01-12-2017
  2      01-12-2018
  2      01-12-2019 
  2      01-12-2020 
  2      01-12-2013
  2      01-12-2014
  2      01-12-2015
  2      01-12-2016
  2      01-12-2017
  2      01-12-2018
  2      01-12-2019 
  2      01-12-2020

Code:-

date = '01-06-2018'
df['Date'] = pd.to_datetime(df['Date'],dayfirst=True)
date = pd.to_datetime(date,dayfirst=True)
if df['Date'].eq(date).any():
    _index =  df[df['Date'].eq(date)].index
else:
    date = (date - pd.DateOffset(months=6))
    _index =  df[df['Date'].eq(date)].index

But in case we change input date from '01-06-2018' to '01-09-2018' or '01-03-2018'. Then it also should become only 01-12-2017 using DateOffset(months=3) and DateOffset(months=9) respectively and should get me the index number of 01-12-2017.

So how can we do that using if elif else conditions? Or using any other way?

Please post code to initialze the dataframe so that we can work with and post working code. — tdelaney
– tdelaney, Commented Jul 5, 2021 at 20:08

Daniel · Accepted Answer · 2021-07-05 20:22:19Z

1

You have to find the largest date less than the given date:

date = df[df['Date'] <= date]['Date'].max()                                                                                                                                                     
index = df[df['Date'] == date].index

answered Jul 5, 2021 at 20:22

Daniel

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1 Comment

Yaser Over a year ago

Thanks Daniel. I got my output using this code.

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