Rolling datediff over rows, multiple keys

Question

I have a dataframe that looks like this:

The dataframe is already sorted by part, then by date.

I need to calculate the days between each date in the previous row.

The date diff calculation would have to restart each time a new part row in encountered.

So the desired output would be:

How would you go about processing this data to achieve the desired output?

Any assistance on this would be greatly appreciated!

Thank you

user_4983450 · Answer

Use groupby + diff:

df.groupby('Part').Date.diff()

0       NaT
1    7 days
2    7 days
3       NaT
4   11 days
5    2 days
Name: Date, dtype: timedelta64[ns]

If you do not have Date as timestamp, you can use df.Date = pd.to_datetime(df.Date) to convert.