Python

Python

你要使用

transform

此方法将返回索引与df对齐的

Series

，然后可以将其添加为新列：

In [74]:df = pd.Dataframe({'Date': ['2015-05-08', '2015-05-07', '2015-05-06', '2015-05-05', '2015-05-08', '2015-05-07', '2015-05-06', '2015-05-05'], 'Sym': ['aapl', 'aapl', 'aapl', 'aapl', 'aaww', 'aaww', 'aaww', 'aaww'], 'Data2': [11, 8, 10, 15, 110, 60, 100, 40],'Data3': [5, 8, 6, 1, 50, 100, 60, 120]})​df['Data4'] = df['Data3'].groupby(df['Date']).transform('sum')dfOut[74]:   Data2  Data3        Date   Sym  Data40     11      5  2015-05-08  aapl     551      8      8  2015-05-07  aapl    1082     10      6  2015-05-06  aapl     663     15      1  2015-05-05  aapl    1214    110     50  2015-05-08  aaww     555     60    100  2015-05-07  aaww    1086    100     60  2015-05-06  aaww     667     40    120  2015-05-05  aaww    121