Pandas: Check if value in one df exists in any column of another DF

September 14, 2022

I have 2 DFs

DF1 & DF2

I have a column in DF1 lets call it ID. I want to check if the IDs from this column are in 2 columns from DF2 (Column names are ID1 & ID2).

I have tried this approach but it’s only returning nan and false values.

DF2['Do_IDs_Exist']  = DF2[['ID1','ID2']].isin(DF1['ID'])

>Solution :

import pandas as pd

data1 = {"ID": [1, 2, 3]}
data2 = {"ID1": [1, 3, 5], "ID2": [2, 4, 6]}
DF1 = pd.DataFrame(data1)
DF1
    ID
0    1
1    2
2    3

DF2 = pd.DataFrame(data2)
DF2
    ID1 ID2
0     1   2
1     3   4
2     5   6

DF2['Do_IDs_Exist'] = (DF2['ID1'].isin(DF1['ID'])) | (DF2['ID2'].isin(DF1['ID']))
DF2
    ID1 ID2 Do_IDs_Exist
0     1   2         True
1     3   4         True
2     5   6        False

This will return True if the ID exist in one of the columns. Replace | with & if the ID should exist in both columns.