Pandas: sum up multiple columns into one column without last column

This may be helpful for beginners, so for the sake of completeness, if you know the column names (e.g. they are in a list), you can use:

column_names = ['Apples', 'Bananas', 'Grapes', 'Kiwis']
df['Fruit Total']= df[column_names].sum(axis=1)

This gives you flexibility about which columns you use as you simply have to manipulate the list column_names and you can do things like pick only columns with the letter 'a' in their name. Another benefit of this is that it's easier for humans to understand what they are doing through column names. Combine this with list(df.columns) to get the column names in a list format. Thus, if you want to drop the last column, all you have to do is:

column_names = list(df.columns)
df['Fruit Total']= df[column_names[:-1]].sum(axis=1)

You can first select by iloc and then sum:

df['Fruit Total']= df.iloc[:, -4:-1].sum(axis=1)
print (df)
   Apples  Bananas  Grapes  Kiwis  Fruit Total
0     2.0      3.0     NaN    1.0          5.0
1     1.0      3.0     7.0    NaN         11.0
2     NaN      NaN     2.0    3.0          2.0

For sum all columns use:

df['Fruit Total']= df.sum(axis=1)