Itterows not populating as expected [duplicate]

I have a pandas dataframe of scores:

data_1 = {"Grad_22": [96, np.nan, np.nan], "Grad_23": [92, 97, np.nan], "Grad_24": [np.nan, 93, 95]}df_1= pd.DataFrame(data_1)df_1["DATE"] = pd.to_datetime(["2022-12-31","2023-12-31","2024-12-31"])df_1.set_index("DATE", inplace=True)            Grad_22  Grad_23  Grad_24DATE                                 2022-12-31     96.0     92.0      NaN2023-12-31      NaN     97.0     93.02024-12-31      NaN      NaN     95.0

I also have a dataframe of grads by years:

data_2 = {"Sr": ["Grad_22","Grad_23"],"Jr": ["Grad_23","Grad_24"]}df_2 = pd.DataFrame(data_2)df_2["DATE"] = pd.to_datetime(["2022-12-31","2023-12-31"])df_2.set_index("DATE", inplace=True)                 Sr       JrDATE                        2022-12-31  Grad_22  Grad_232023-12-31  Grad_23  Grad_24

I would like to use the rows from df_2 as labels for df_1 to populate df_3

data_3= {"Sr": [0, 0], "Jr": [0, 0]}df_3 = pd.DataFrame(data_3)df_3 ["DATE"] = pd.to_datetime(["2022-12-31","2023-12-31"])df_3.set_index("DATE", inplace=True)print(df_3)'''Iterrows seems perfect for this:'''for index, row in df_2.iterrows():    df_3.loc[index] = df_1.loc[index, row] print(df_3)

I would expect:

                Sr       JrDATE                        2022-12-31  96.0  92.02023-12-31  97.0  93.0

Instead, i get:

                Sr       JrDATE              2022-12-31 NaN NaN2023-12-31 NaN NaN

How should I be assigning to df_3 and why am I getting NaN?