Find and copy values between 2 dataframes

Question

I’m having trouble copying some data between 2 dataframes. I have the main_df:

id             date  stuff 
123             NaN      3
456      2022-10-10      6
789      2022-09-15      2
357             NaN      9
159      2022-09-15      3

and second_df:

I want to search if an id in second_df is in main_df and copy the date that appear in main_df to second_df. This would be the result:

id   stuff         date
321      3          NaN
456      6   2022-10-10
789      2   2022-09-15
351      4          NaN

I know that with second_df["id"].isin(main_id["id"]) I can get a dataframe/column/Series with boolean results indicating if the id exists, but I don’t know how to copy the date value.

Hope someone can help me, thanks.

Asked By: Alex Turner

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Source

Answer 1

you can use map to bring over the date value

df2['date']=df2['id'].map(df.set_index('id')['date'])
df2

id  stuff   date
0   321     3   NaN
1   456     6   2022-10-10
2   789     2   2022-09-15
3   351     4   NaN

Answered By: Naveed

Find and copy values between 2 dataframes

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