用途：

#function for formating timedeltas
def f(x):
    ts = x.total_seconds()
    hours, remainder = divmod(ts, 3600)
    minutes, seconds = divmod(remainder, 60)
    return ('{:02d}:{:02d}:{:02d}').format(int(hours), int(minutes), int(seconds))

#convert Place columns to numeric
cols1 = df.filter(like='Place').columns
df[cols1] = df[cols1].apply(pd.to_numeric)

#convert time columns to timedeltas and then to unix time
cols = df.filter(like='time').columns
df[cols] = df[cols].fillna('0').apply(pd.to_timedelta).astype(np.int64)

#aggregate sum
df = df.groupby('racer', dropna=True).sum()

#convert timedeltas to times with formating
df[cols] = df[cols].apply(lambda x: pd.to_timedelta(x).map(f))
print (df)
          race_time_1 race_time_2  1st_Place  2nd_Place
racer                                                  
joe shmo     00:24:12    01:03:04          1          1
sally sue    00:00:00    00:29:54          1          0