I'm trying to merge 2 or more dataframes on different columns in one pass. For example let's assume we have 3 datasets:

df1

id     col_a    col_b    col_c ... 
1      3        0        1
2      4        1        1
3      3        1        2
4      0        0        0
5      1        2        0
6      1        2        0
.
.
.

df2

id     col_d    id_2
1      3        a
2      4        b
3      3        c
3      0        d
4      1        e
5      1        f
.
.
.

df3

id_2   col_3
a      3
b      4
c      3
d      0
e      1
f      1
.
.
.

I want to chain connect the 3 data frames on columns id between df1 and df2 and then connect that to df3 on id_2. I know how to create a new dataframe after the first merge and then merge the result with df3, but is there a way to chain this in one function?

CodePudding user response：

Chain the operation. Here I use outer. You can change to what is most preferable now that you did not state.

df1.merge(df2, how='outer', on='id').merge(df3, how='outer', on='id_2')

    id  col_a  col_b  col_c  col_d id_2  col_3
0   1      3      0      1    3.0    a    3.0
1   2      4      1      1    4.0    b    4.0
2   3      3      1      2    3.0    c    3.0
3   3      3      1      2    0.0    d    0.0
4   4      0      0      0    1.0    e    1.0
5   5      1      2      0    1.0    f    1.0
6   6      1      2      0    NaN  NaN    NaN