Is there a way to do vlookup using python?

Question

Lets say I have two dataframes df1 and df2 and I need to do vlookup on name and give out names which are matching.

import pandas as pd
import numpy as np

df1 = pd.DataFrame({
    'name': ['A', 'B', 'C', 'D'],
    'val1': [5, 6, 7, 8],
    'val2': [1, 2, 3, 4],
})

df2 = pd.DataFrame({
    'name': ['B', 'D', 'E', 'F'],
    'abc': [15, 16, 17, 18],
    'def': [11, 21, 31, 41],
})

Expected Output:
name    val1    val2    matched_name
A          5       1    NaN
B          6       2    B
C          7       3    NaN
D          8       4    D

I thought this could be done by:

df1['matched_name'] = df1['name'].map(df2['name'])

But I’m getting all NaN’s in matched column. Is there a way to do this?

Asked By: Akilesh

||

Source

Answer 1

It’s not really a vlookup, but you can use where and isin:

df1['matched_name'] = df1['name'].where(df1['name'].isin(df2['name']))

A more convoluted way, using a merge, which allows you to also add other columns if needed:

out = df1.merge(df2[['name']].rename(columns={'name': 'matched_name'}),
                left_on='name', right_on='matched_name', how='left')

Output:

  name  val1  val2 matched_name
0    A     5     1          NaN
1    B     6     2            B
2    C     7     3          NaN
3    D     8     4            D

Answered By: mozway

Answer 2

You can use the numpy where which will see if the name exists in the other dataframes name column and since the names are exact match, you can use the value in first dataframe:

df1['matched_name']=np.where(df1.name.isin(df2.name),df1.name,np.nan)

This gives the output as:

  name  val1  val2 matched_name
0    A     5     1          NaN
1    B     6     2            B
2    C     7     3          NaN
3    D     8     4            D

Answered By: Suraj Kumar

Is there a way to do vlookup using python?

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