compare one column value with all the values of other column using pandas

Question

I have the one excel file which contains the below values

I need to compare a_id value with all the value of b_id and if it matche

Answer 1

Use Series.isin for test membership:

df1['a_flag'] = df3['a_id'].isin(df3['b_id']).astype(int)
df1['b_flag'] = df3['b_id'].isin(df3['a_id']).astype(int)