从两个不同的数据帧构建三元组

我要构建三元组：源->目标->边缘，并将这些三元组存储在新的数据框中。

我有两个数据框

     Accident_ID Location  CarID_1  CarID_2  DriverID_1  DriverID_2
0            1    Tartu     1000     1001           1           3
1            2   Tallin     1002     1003           2           5
2            3    Tartu     1004     1005           4           6
3            4   Tallin     1006     1007           7           8



    User_ID First Name Last Name  Age           Address  Accident_ID     ROLE
0        1    Chester    Murphy   25  Narva 108, Tartu            1   Driver
1        2     Walter    Turner   26   Tilgi 49, Tartu            2   Driver
2        3      Daryl    Fowler   25    Piik 67, Tartu            1   Driver
3        4        Ted    Nelson   45   Herne 20, Tartu            3   Driver
4        5     Olivia  Crawford   38  Kalevi 25, Tartu            2   Driver
5        1    Chester    Murphy   25  Narva 108, Tartu            2  Witness
6        6        Amy    Miller   27   Riia 408, Tartu            3   Driver
7        7        Tes     Smith   25  Narva 108, Tartu            4   Driver
8        8       Josh     Blake   36  Parnu 37, Tallin            4   Driver
9        3      Daryl    Fowler   25    Piik 67, Tartu            4  Witness

我必须形成的三元组就是这种模式 [！[在此处输入图片描述] [2]] [2]

这是什么python代码？我已经写了这个，但是我得到的错误见证没有定义

df3 = df1.merge(df2,on='Accident_ID')
df3["train"] = df3.Accident_ID < 5 
df3["train"] .value_counts()

triples = []
for _, row in df3[df3["train"]].iterrows():

    if row["ROLE"] == "Driver":
        if row["User_ID"] == row["DriverID_1"]:
            Drives = (row["User_ID"],row["CarID_1"], "Drives")
        elif row["User_ID"] == row["DriverID_2"]:  
            Drives = (row["User_ID"],row["CarID_2"], "Drives")
    else:    
        Witness = (row["User_ID"],row["Accident_ID"], "Witness") 

    Involved_in_first = (row["CarID_1"],row["Accident_ID"], "Involved in")
    Involved_in_second = (row["CarID_2"],row["Accident_ID"], "Involved in")
    Happened_in = (row["Accident_ID"],row["Location"], "Happened in")
    Lives_in = (row["User_ID"],row["Address"], "Lives in")
    triples.extend((Drives , Witness  , Involved_in_first,Involved_in_second, Happened_in , Lives_in ))


triples_df = pd.DataFrame(triples, columns=["Source", "Target", "Edge"])
triples_df.shape