I have a dataframe A:

a 1
a 2
b 1
b 2

Another dataframe B:

a 3
a 4 
b 3

I want my result dataframe to be like

a 1 3
a 1 4 
a 2 3
a 2 4 
b 1 3 
b 2 3 

I wondering how I can get the desired result in python. Thanks a lot!

A simple merge using df.merge does this:

df1.merge(df2, on=['A'])A  B_x  B_y
0  a    1    3
1  a    1    4
2  a    2    3
3  a    2    4
4  b    1    3
5  b    2    3