像这样的东西怎么样？

import datetime as dt
import pandas as pd

df = pd.DataFrame([[1, '16:45'],
                   [2, '21:03:39']], columns=['x1', 'time_string'])
df['time'] = pd.to_datetime(df['time_string']).apply(lambda t: dt.time(t.hour, t.minute, t.second))

# Output these to show it works
df.head()
df['time'].apply(lambda x: type(x))

返回以下内容：

x1 time_string      time
0   1       16:45  16:45:00
1   2    21:03:39  21:03:39

0    <class 'datetime.time'>
1    <class 'datetime.time'>
Name: time, dtype: object