如何连接两个具有相同列的 Pandas 数据帧，但前提是两个数据帧中的一列的值相同？

Question

I have two dataframes like the below:

DF1:

col1	col2
22	yes
22	no
24	yes
22	no
27	no

DF2:

col1	col2
28	yes
22	no
29	yes
22	yes
27	yes

I want to concat both dataframes, so that I end up with the below. I don't want to join the dataframes on col1, as that doubles the number of columns. I just want to combine the dataframe vertically if they share a common value on "col1." Any help on this?

DF3:

col1	col2
22	yes
22	no
22	no
22	no
22	yes
27	no
27	yes

Answer 1

Let us first find the common values using set intersection then concat the required rows from df1 and df2 and optionally sort the values

i = set(df1['col1']) & set(df2['col1'])
pd.concat([df1[df1['col1'].isin(i)], df2[df2['col1'].isin(i)]]).sort_values('col1')

---

   col1 col2
0    22  yes
1    22   no
3    22   no
1    22   no
3    22  yes
4    27   no
4    27  yes