python中where函数_如何在python中基于Where函数获取两列值

问题是&＃xff1a;

基于user_id列&＃xff0c;我想得到rating和{}列的值。可能有多个条目具有相同的用户标识。我希望获取具有rating和product_id列值的所有用户记录&＃xff0c;但对于用户未对电影进行评级的电影&＃xff0c;应将其显示为Nan&＃xff0c;但仍应检索product_id。下表提供了一些数据。在| product_id | user_id | user_name | rating |

|-------------|-----------------|----------------------------------------------|--------|

| B0009XRZ92 | A2JFZLAUG3YFQ7 | Entropy Babe "EB" | 5 |

| B0009XRZ92 | A22HGAAO8KZ2N3 | R. Metzelar | 5 |

| B000067A8B | A2NJO6YE954DBH | Lawrance M. Bernabo | 4 |

| B0009XRZ92 | A3HE4MYMWK4AER | Rebecca M. Eddy "Foster Mom and Untbunny" | 5 |

| B003A3R3ZY | A9A2PR663ED1V | Roger D. Goff | 5 |

| B0009XRZ92 | A2MRZDJF90JC1U | Suzanne K. Armstrong "Suzy Q" | 5 |

| B0009XRZ92 | A2YNBDT3170PCR | C. O&＃39;Hern | 5 |

| B0009XRZ92 | A10VJ7BDVCPKEZ | Carol S. Bottom | 5 |

| B0009XRZ92 | AAAQO894MG80B | Paul J. Michko | 5 |

| B00067BBQE | A9A2PR663ED1V | Roger D. Goff | 5 |

| B0009XRZ92 | A31S5QUMFR8NH2 | Dana L. Jordan "Mom of Twins" | 5 |

| B0009XRZ92 | A2DS24DHXUH0GM | Gaz Rev(iewer) | 4 |

| B00006AUMZ | A2NJO6YE954DBH | Lawrance M. Bernabo | 4 |

| B0009XRZ92 | A16FRHL2ZC7EUR | M. Claytor | 5 |

| B0009XRZ92 | A3AV8R0A62PP1N | MARCUSHELBLINZ "mmmacman" | 5 |

| B0009XRZ92 | A3QN84C38DE9FU | Gillian M. Kratzer | 5 |

| B0009XRZ92 | A36MLTLVQFEQYL | Yossarian "alienated socialist" | 5 |

| B00006AUMD | A2NJO6YE954DBH | Lawrance M. Bernabo | 4 |What I want to do is:

To take one user_id at a time and display the rating and product_id

columns value for that user for all the movies in the table and if the

user didn&＃39;t rate some movies then the record should be displayed with

the product_id value and rating as Nan and the whole process should be repeated for all the users.

例如&＃xff0c;user_id: A2NJO6YE954DBH的记录如下所示&＃xff1a;

^{pr2}$

我试着用Pandas库来编写代码&＃xff0c;但还是忍不住。这是我所做的一切&＃xff0c;但它没有输出我想要的。在import pandas as pd

df &＃61;pd.read_csv(&＃39;out.csv&＃39;)

unique_users&＃61;df.user_id.unique()

for x, y in enumerate(unique_users):

print(df[[&＃39;rating&＃39;,&＃39;product_id&＃39;]].where(df.user_id&＃61;&＃61;y))

请帮帮我。。谢谢