How to add values to the pandas dataframe coulmn depending upon value of column in other dataframe

Question

I have pandas dataframe somthing like this. This dataframe contains unique user_id and corresponding user-name

df user_id user_name 1 Jack 2 Neil 3 Peter 4 Smith 5 Neev

And I have second dataframe something like this

 df1 user_id item_id user_name 1 23 Null 1 24 Null 2 34 Null 3 35 Null 5 45 Null

I want to fill user_name column above from the 1st dataframe. So,where user_id is matched it should enter corresponding user_name in that position.

So it should look like this..

df1 user_id item_id user_name 1 23 Jack 1 24 Jack 2 34 Neil 3 35 Peter 5 45 Neev

I am doin following in python

 b = df.user_name[df['user_id'].isin(df1['user_id'])] df1['user_name'] = b

But,It drops duplicates. I don't want to do that. Please help.

Bob Baxley · Accepted Answer · 2016-01-29 03:23:18Z

3

Use merge:

In [299]: df1[['user_id','item_id']].merge(df,on='user_id') Out[299]: user_id item_id user_name 0 1 23 Jack 1 1 24 Jack 2 2 34 Neil 3 3 35 Peter 4 5 45 Neev

answered Jan 29, 2016 at 3:23

Bob Baxley

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1 Comment

Neil Over a year ago

Awesome.. Thanks for the answer. really helped me.

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