下面的代码应该可以解决问题
s1 = pd.Series([5, 1, 'a'])s2 = pd.Series([6, 2, 'b'])s3 = pd.Series([7, 3, 'd'])s4 = pd.Series([8, 4, 'e'])s5 = pd.Series([9, 5, 'f'])df1 = pd.Dataframe([list(s1), list(s2),list(s3),list(s4),list(s5)], columns = ["A", "B", "C"])s1 = pd.Series([5, 6, 'p'])s2 = pd.Series([6, 7, 'q'])s3 = pd.Series([7, 8, 'r'])s4 = pd.Series([8, 9, 's'])s5 = pd.Series([9, 10, 't'])df2 = pd.Dataframe([list(s1), list(s2),list(s3),list(s4),list(s5)], columns = ["A", "B", "C"])df1.loc[df1.A.isin(df2.A), ['B', 'C']] = df2[['B', 'C']]print df1
输出
A B C0 5 6 p1 6 7 q2 7 8 r3 8 9 s4 9 10 t
编辑评论：
要替换整行而不是仅替换某些列：
cols = list(df1.columns) df1.loc[df1.A.isin(df2.A), cols] = df2[cols]
