pandas: merge (join) two data frames on multiple columns

Michael Zippo

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I am trying to join two pandas data frames using two columns:

new_df = pd.merge(A_df, B_df,  how="left", left_on="[A_c1,c2]", right_on = "[B_c1,c2]")

but got the following error:

pandas/index.pyx in pandas.index.IndexEngine.get_loc (pandas/index.c:4164)()

pandas/index.pyx in pandas.index.IndexEngine.get_loc (pandas/index.c:4028)()

pandas/src/hashtable_class_helper.pxi in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:13166)()

pandas/src/hashtable_class_helper.pxi in pandas.hashtable.PyObjectHashTable.get_item (pandas/hashtable.c:13120)()

KeyError: "[B_1, c2]"

Any idea what should be the right way to do this? Thanks!

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Manuel Danburry

California | 2023-04-01

I was preparing for my coding interview, thanks for clarifying this - pandas: merge (join) two data frames on multiple columns in Python is not the simplest one. Will use it in my bachelor thesis

Marie Schteiner

Berlin | 2023-04-01

re Python module is always a bit confusing 😭 pandas: merge (join) two data frames on multiple columns is not the only problem I encountered. Will get back tomorrow with feedback

Oliver Sikorski

Abu Dhabi | 2023-04-01

Simply put and clear. Thank you for sharing. pandas: merge (join) two data frames on multiple columns and other issues with code Python module was always my weak point 😁. I am just not quite sure it is the best method