Expand dataframe by lookup in another dataframe

Question

I have two dataframes:

df1
engine       id
F1 D2 J3     100234
F1 D2 J3     100238
K2 JM F2     200788
K2 JM F2     200790

df2
engine       id
F1 D2 J3     100234
F1 D2 J3     100244
K2 JM F2     200788
K2 JM F2     200850
K2 JM F2     200690

I would like to extend df1 with rows from df2 that are not found in df1 for that engine and id combination. Resulting df would not contain duplicates and would look something like this:

engine       id
F1 D2 J3     100234
F1 D2 J3     100238
K2 JM F2     200788
K2 JM F2     200790
F1 D2 J3     100244
K2 JM F2     200850
K2 JM F2     200690

How can I achieve this?

Asked By: detrraxic

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Source

Answer 1

You can use pd.merge by specifying your two columns and with how="outer":

pd.merge(df1, df2, on=['engine', 'id'], how='outer')

Output:

     engine      id
0  F1 D2 J3  100234
1  F1 D2 J3  100238
2  K2 JM F2  200788
3  K2 JM F2  200790
4  F1 D2 J3  100244
5  K2 JM F2  200850
6  K2 JM F2  200690

Answered By: Tranbi

Answer 2

You can do an outer join

out = df1.join(df2, on=['engine', 'id'], how='outer')

Answered By: oskros

Expand dataframe by lookup in another dataframe

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