python - Pandas dataframe total row

Question

I have a dataframe, something like:

     foo  bar  qux
0    a    1    3.14
1    b    3    2.72
2    c    2    1.62
3    d    9    1.41
4    e    3    0.58

and I would like to add a 'total' row to the end of dataframe:

     foo  bar  qux
0    a    1    3.14
1    b    3    2.72
2    c    2    1.62
3    d    9    1.41
4    e    3    0.58
5  total  18   9.47

I've tried to use the sum command but I end up with a Series, which although I can convert back to a Dataframe, doesn't maintain the data types:

tot_row = pd.DataFrame(df.sum()).T
tot_row['foo'] = 'tot'
tot_row.dtypes:
     foo    object
     bar    object
     qux    object

I would like to maintain the data types from the original data frame as I need to apply other operations to the total row, something like:

baz = 2*tot_row['qux'] + 3*tot_row['bar']

Answer 1

Append a totals row with

df.append(df.sum(numeric_only=True), ignore_index=True)

The conversion is necessary only if you have a column of strings or objects.

It's a bit of a fragile solution so I'd recommend sticking to operations on the dataframe, though. eg.

baz = 2*df['qux'].sum() + 3*df['bar'].sum()