Python 警告

Question

Input:myfile

Expected output:

amountFile=pd.read_excel("myfile")
amountFile['total_amount']=amountFile.groupby('ID')["item_amount"].transform('sum')
amountFile.to_excel('file location')

above is my code to calculate new total amount column by taking sum of item amount in each item. It works fine but I am getting warning,so I am afraid is it a problem.

see the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy amountFile['total_amount']=amountFile['total_amount']=amountFile.groupby('ID')["item_amount"].transform('sum') C:/Users/JasnaRaghavan/PycharmProjects/PobImportScript/testReconsile.py:40: SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame. Try using.loc[row_indexer,col_indexer] = value instead

Answer 1

I've run your code but didn't get the same error. If you're getting that warning though, it means Pandas can't guarantee whether you are working on the column itself (ie a slice of the DataFrame) or a copy of the slice.

You could try using .loc to access the column instead. Your code would look something like this:

amountFile.loc[:, 'total_amount'] = amountFile.groupby('ID')["item_amount"].transform('sum')