Python Pandas .loc using a different dataframe

I'm trying to assign dataframe columns to the row and column of the .loc function. I have a dataframe df with no set index, with Sites and Visits as my column headers

Index	Site	Visit
0	101	Visit 1
1	102	Visit 1
2	102	Visit 2

I have another dataframe df2 with Sites as my dataframe index, and Visits as my columns with Cost as my values.

Index	Visit 1	Visit 2
101	50	60
102	100	120

I'm trying to use .loc to index the Cost from df2 and add it as a column to df1 like so

Index	Site	Visit	Cost
0	101	Visit 1	50
1	102	Visit 1	60
2	102	Visit 2	120

I tried using the following code to provide a row and column value

df['Cost'] = df2.loc[df['Site'],df['Visit']]  

But i got the following error:

KeyError: "Passing list-likes to .loc or [] with any missing labels is no longer supported.   The following labels were missing: etc. etc.   

Any idea how to use two column values from one dataframe as the .loc row and column values?

Thanks so much for your help!

https://stackoverflow.com/questions/66020134/python-pandas-loc-using-a-different-dataframe February 03, 2021 at 09:47AM