Suppose we have:
>>> df1
A B
0 1 a
1 2 a
2 3 a
3 4 a
>>> df2
A B
0 1 b
1 2 b
2 3 b
3 5 b
I would like to merge them on "A" and then list them by interleaving rows like:
A B
0 1 a
0 1 b
1 2 a
1 2 b
2 3 a
2 3 b
I tried merge but it list them column by column. For example if I have 3 or more data frames, merge can merge them on some columns, but my problem would be then to interleave them
If need match by A filter rows by Series.isin in boolean indexing, pass to concat with DataFrame.sort_index:
df = pd.concat([df1[df1.A.isin(df2.A)],
df2[df2.A.isin(df1.A)]]).sort_index(kind='stable')
print (df)
A B
0 1 a
0 1 b
1 2 a
1 2 b
2 3 a
2 3 b
EDIT:
For general data is possible sorting by A and create default index for correct interleaving:
df = (pd.concat([df1[df1.A.isin(df2.A)].sort_values('A', kind='stable').reset_index(drop=True),
df2[df2.A.isin(df1.A)].sort_values('A', kind='stable').reset_index(drop=True)])
.sort_index(kind='stable'))
