python pandas：合並2個數據框

Question

我想使用python的pandas加入如下所示的2個數據框：

customer_orders = pd.DataFrame({'customerID': [1, 2, 2, 1],
                    'customerName': ['John', 'Anna', 'Anna', 'John'],
                    'customerAge': [21, 45, 45, 21],
                    'orderID': [255, 256, 257, 258],
                    'paymentType': ['visa', 'bank', 'master', 'paypal']})

會產生：

 customerAge  customerID customerName  orderID paymentType
0           21           1         John      255        visa
1           45           2         Anna      256        bank
2           45           2         Anna      257      master
3           21           1         John      258      paypal

和

order_products = pd.DataFrame({'orderID': [255, 255, 257, 258, 255, 257],
                           'price': [9.99, 23.40, 15.89, 3.99, 89.50, 23.40],
                           'productName': ['filter', 'cosmetic', 'shampoo', 'tissues', 'elecBrush', 'cosmetic']})

會產生：

   orderID  price productName
0      255   9.99      filter
1      255  23.40    cosmetic
2      257  15.89     shampoo
3      258   3.99     tissues
4      255  89.50   elecBrush
5      257  23.40    cosmetic

到下面的東西
預期產量

 customerAge  customerID customerName  orderID paymentType
           21           1         John      255        visa     255   9.99      filter
           21           1         John      255        visa     255  23.40    cosmetic
           21           1         John      255        visa     255  89.50   elecBrush
           45           2         Anna      256        bank     null  null         null
           45           2         Anna      257      master     257  15.89     shampoo
           45           2         Anna      257      master     257  23.40    cosmetic  
           21           1         John      258      paypal     258   3.99     tissues

據我所知，這是一個SQL左連接。 但是使用

all = customer_orders.join(order_products, on="orderID", how='left', lsuffix='_left', rsuffix='_right')

沒有給我我想要的東西（行和NaN太少，而不是第二張表的值）。

我想念什么？

Answer 1

剩下？ 不，這是一個外部聯接。

customer_orders.merge(order_products, on="orderID", how='outer')

   customerAge  customerID customerName  orderID paymentType  price  \
0           21           1         John      255        visa   9.99   
1           21           1         John      255        visa  23.40   
2           21           1         John      255        visa  89.50   
3           45           2         Anna      256        bank    NaN   
4           45           2         Anna      257      master  15.89   
5           45           2         Anna      257      master  23.40   
6           21           1         John      258      paypal   3.99   

  productName  
0      filter  
1    cosmetic  
2   elecBrush  
3         NaN  
4     shampoo  
5    cosmetic  
6     tissues  

Answer 2

嘗試使用merge

all = customer_orders.merge(order_products, on="orderID", how='left')