Pandas fill Mutliindex column data frame from single index column data frame

I have two data frames with same row index.

First dataframe :

df1 = pd.DataFrame(index=['a', 'b', 'c'], columns=pd.MultiIndex.from_product([['2023-12-31','2024-01-31'], ['myvalue1', 'myvalue2']]))

Second dataframe :

df2 = pd.DataFrame(index=['a', 'b', 'c'], data=
                   {'myvalue1':[2,3, 4], 'myvalue2':[6,7,8]})

Remembering that row indices are the same, I wanted to fill first dataframe with second, like that :

df1.loc[:,(slice(None),'myvalue1')] = df2['myvalue1']
df1.loc[:,(slice(None),'myvalue2')] = df2['myvalue2']

I get the error : ValueError: Must have equal len keys and value when setting with an iterable

Expected result for df1 :

    2023-12-31          2024-01-31
   myvalue1   myvalue2  myvalue1    myvalue2
a   2          6          2           6
b   3          7          3           7
c   4          8          4           8

Do you know how to proceed (avoiding for loop) ?

Thank you

>Solution :

I’m pretty sure you can avoid using an intermediate template (i.e, the input df1) but if you can’t, here is one option with reindex/set_axis :

df1 = (
    df2
        .reindex(df1.columns.get_level_values(1), axis=1)
        .set_axis(df1.columns, axis=1)
)

Output :

  2023-12-31          2024-01-31         
    myvalue1 myvalue2   myvalue1 myvalue2
a          2        6          2        6
b          3        7          3        7
c          4        8          4        8