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I just started learning Python so forgive me if this question has already been answered somewhere else. I want to create a new column called "Sum", which will simply be the previous columns added up.

Risk_Parity.tail() VCIT VCLT PCY RWR IJR XLU EWL Date 2017-01-31 21.704155 11.733716 9.588649 8.278629 5.061788 7.010918 7.951747 2017-02-28 19.839319 10.748690 9.582891 7.548530 5.066478 7.453951 7.950232 2017-03-31 19.986782 10.754507 9.593623 7.370828 5.024079 7.402774 7.654366 2017-04-30 18.897307 11.102380 10.021139 9.666693 5.901137 7.398604 11.284331 2017-05-31 63.962659 23.670240 46.018698 9.917160 15.234977 12.344524 20.405587

The table columns are a little off but all I need is (21.70 + 11.73...+7.95) I can only get as far as creating the column Risk_Parity['sum'] = , but then I'm lost.

I'd rather not do have to do Risk_Parity['sum] = Risk_Parity['VCIT'] + Risk_Parity['VCLT']...

After creating the sum column, I want to divide each column by the sum column and make that into a new dataframe, which wouldn't include the sum column.

If anyone could help, I'd greatly appreciate it. Please try to dumb your answers down as much as possible lol.

Thanks!

Tom

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  • Have you tried Risk_Parity.sum(1)? Commented Jun 12, 2017 at 16:03

2 Answers 2

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Use sum with the parameter axis=1 to specify summation over rows

Risk_Parity['Sum'] = Risk_Parity.sum(1)

To create a new copy of Risk_Parity without writing a new column to the original

Risk_Parity.assign(Sum= Risk_Parity.sum(1))

Notice also, that I named the column Sum and not sum. I did this to avoid colliding with the very same method named sum I used to create the column.

To only include numeric columns... however, sum knows to skip non-numeric columns anyway.

RiskParity.assign(Sum=RiskParity.select_dtypes(['number']).sum(1)) # same as # RiskParity.assign(Sum=RiskParity.sum(1)) VCIT VCLT PCY RWR IJR XLU EWL Sum Date 2017-01-31 21.70 11.73 9.59 8.28 5.06 7.01 7.95 71.33 2017-02-28 19.84 10.75 9.58 7.55 5.07 7.45 7.95 68.19 2017-03-31 19.99 10.75 9.59 7.37 5.02 7.40 7.65 67.79 2017-04-30 18.90 11.10 10.02 9.67 5.90 7.40 11.28 74.27 2017-05-31 63.96 23.67 46.02 9.92 15.23 12.34 20.41 191.55
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will this know not to include the Date column or any potential character columns? Just out of interest, I'm not that familiar with pandas.
The Date column is not a column, it's in the index. So yes. As for the non-character columns... I'll update my post.
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l = ['VCIT' , VCLT' ,PCY' ... 'EWL'] Risk_Parity['sum'] = 0 for item in l: Risk_Parity['sum'] += Risk_Parity[item]
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