'Shift values in one pandas df column down based on values of another column

I have a dataframe:

{
  'Person': {
    0: 1, 1: 1, 2: 1, 3: 1, 4: 2, 5: 2, 6: 2, 
    7: 2, 8: 3, 9: 3, 10: 3, 11: 3
  }, 
  'Year': {
    0: 2017, 1: 2018, 2: 2019, 3: 2020, 4: 2017, 5: 2018, 6: 2019, 
    7: 2020, 8: 2017, 9: 2018, 10: 2019, 11: 2020
  }, 
  'Value': {
    0: 20, 1: 30, 2: 23, 3: 40, 4: 11, 5: 20, 6: 30, 
    7: 21, 8: 12, 9: 12, 10: 15, 11: 23
  }
}

I want to shift Value column by 1 down row, but taking into account 'Author`.

I tried shift and roll, but did not get the necessary result.

Expected output:

{
  'Person': {
    0: 1, 1: 1, 2: 1, 3: 1, 4: 2, 5: 2, 6: 2, 
    7: 2, 8: 3, 9: 3, 10: 3, 11: 3
  }, 
  'Year': {
    0: 2017, 1: 2018, 2: 2019, 3: 2020, 4: 2017, 5: 2018, 6: 2019, 
    7: 2020, 8: 2017, 9: 2018, 10: 2019, 11: 2020
  }, 
  'Value': {
    0: 20, 1: 30, 2: 23, 3: 40, 4: 11, 5: 20, 6: 30, 
    7: 21, 8: 12, 9: 12, 10: 15, 11: 23
  }, 
  'Value t-1': {
    0: nan, 1: 20.0, 2: 30.0, 3: 23.0, 4: nan, 5: 11.0, 6: 20.0, 
    7: 30.0, 8: nan, 9: 12.0, 10: 12.0, 11: 15.0
  }
}

python pandas

Solution 1:^[1]

Full credit goes to @enke

df['Value t-1'] = df.groupby('Person')['Value'].shift()

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Solution	Source
Solution 1	Anakin Skywalker

'Shift values in one pandas df column down based on values of another column

Solution 1:[1]

Sources

Related Questions

Solution 1:^[1]