获取python groupby中字符串的第一次和最后一次出现

Question

I have a python dataframe with the following columns(Attendance data)

Empcode     T01         T01          T02          T03          T04
TranDate    10/09/2018  10/09/2018   10/09/2018   10/09/2018   10/09/2018
Trn Time    09.29       17.54        13.52        10.01        18.01

I want to get the first occurence of Trn Time as In Time and last occurence of TrnTime as Out time for a given Trandate and Empcode.

if there is only one record for the key the time should come in Out Time.

g=df.groupby(['Empcode','TrnDate'])

print (pd.DataFrame({'In':g.TrnTime.nth(0),'out':g.TrnTime.nth(-1)}))

The above code works wherever there are 2 records for a Empcode and TranDate.

If there is a single record, it does not work.

Answer 1

if there is only one record for the key the time should come in Out Time

Then let it be so. Define a function that does exactly this and pass it to GroupBy.apply :

def fnc(g):
    res = {'Out': g.iat[-1]}
    if len(g) > 1:
        res['In'] = g.iat[0]
    return res

dfres = df.groupby(['Empcode','TranDate'])['Trn Time'].apply(fnc).unstack()
print(dfres)
                       In    Out
Empcode TranDate                
T01     10/09/2018  09.29  17.54
T02     10/09/2018    NaN  13.52
T03     10/09/2018    NaN  10.01
T04     10/09/2018    NaN  18.01