python之根据单元格值向 Pandas 数据框添加一列

这是我的东西:

list1_ = [("1","a","a1"),("1","b","b1"),("1","c","c"),("2","a","a2")] 
df1 = pd.DataFrame(list1_,columns = ["user","col1","col2"]) 
list2_ = [("1","b","b2"),("1","a","a2"),("2","a","a3"),("1","c","c2")] 
df2 = pd.DataFrame(list2_,columns = ["user","col1","col3"]) 

我想做的是让 df2 中的 (user,col1) 与 df1 匹配并在 df1 中添加 col3... 基本上使 df1: (user, col1,col2,col3) 具有相同的单元格值. 最终结果应该是这样的:

list3_ = [("1","a","a1","a2"),("1","b","b1","b2"),("1","c","c","c2"),  
("2","a","a2","a3")] 
df3 = pd.DataFrame(list3_,columns = ["user","col1","col2","col3"]) 

请注意:我从 csv 文件读取 df1，并使用 list2_ 创建 df2。因此，我有一些 list2_ 形式的数据，但没有 list1_ 形式的数据。因此，只想使用 df1、list2_ 和/或 df2。