I am merging a dataframe with a static dataframe (a table in a spreadsheet) that results in a dataframe that looks like this:

Counterparty    DealType       Commodity   Product     
        Aron      Buy           AAA         NaN  
        Aron      Buy           AAA         NaN  
        Aron      Buy           AAA         NaN  
        Aron      Buy           BBB         prod1  
        Aron      Buy           BBB         prod1  
        Aron      Buy           BBB         prod1  
        Aron      Buy          CCC          NaN  
        Aron      Buy          CCC          NaN  
        Aron      Buy          CCC          NaN 

If the dataframe has no NaN values in the Product Column then the merge was successful and my program can continue.

However, if NaN values do exist in the product column I need to update my spreadsheet with the missing values.

this is the code I have which returns true if there is any NaN values:

if (df['Commodity'].isnull().any()):
    print('missing values found')
    # get list of missing values
    sys.exit(0)

but I want to return a list of the missing values like ['AAA', 'CCC']