Pandas Time difference of each column

Question

I have this dataframe:

ID	STEP 1	STEP 2	...	STEP 40
1	2022-03-08 09:23:35	2022-03-08 10:23:35	...	2022-03-19 09:23:35
2	2022-03-08 09:23:35	2022-03-08 11:23:35	...	2022-03-18 09:23:35

I want to turn it into this:

ID	Time 1-2	Time 1-3	...	Time 39-40
1	296 days 08:08:05	297 days 08:08:05	...	297 days 08:08:05
2	296 days 08:08:05	297 days 08:08:05	...	297 days 08:08:05

I created a new dataframe:

index=[]
for item1 in range (1,40):
    for item2 in range (1,40):
        if item1  < item2:
            index.append("Time from Step "+ str(item1)+" to step "+ str(item2))

df = pd.DataFrame(-1, index=np.arange(len(caseList)), columns=index)

But I don´t know how to fill in the times.

Answer 1

Use vectorial code.

If you don't have datetime type, uncomment the second step:

out = (
 df.set_index('ID')
   #.apply(lambda c: pd.to_datetime(c))
   .diff(axis=1).iloc[:, 1:]
   .set_axis([f'Time {i+1}-{i+2}' for i in range(len(df.columns)-2)], axis=1)
   .reset_index()
)

output:

   ID        Time 1-2         Time 2-3
0   1 0 days 01:00:00 10 days 23:00:00
1   2 0 days 02:00:00  9 days 22:00:00

NB. I used "STEP 40" as "STEP 3" for the example here