Use pandas.shift() within a group

by

Pandas’ grouped objects have a groupby.DataFrameGroupBy.shift method, which will shift a specified column in each group n periods, just like the regular dataframe’s shift method:

df['prev_value'] = df.groupby('object')['value'].shift()

For the following example dataframe:

print(df)

     object  period  value
0       1       1     24
1       1       2     67
2       1       4     89
3       2       4      5
4       2      23     23

The result would be:

     object  period  value  prev_value
0       1       1     24         NaN
1       1       2     67        24.0
2       1       4     89        67.0
3       2       4      5         NaN
4       2      23     23         5.0

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