How to Calculate NPV?

[ryguy7272]

I am using Spyder Python 2.7.  I'm running this sample code.

import scipy as sp
cashflows=[50,40,20,10,50]
npv=sp.npv(0.1,cashflows)
round(npv,2)


Now, I'm trying to get the NPV, and I don't see any obvious way to get it.  
The author of the book that I'm reading gets 144.56.  I think that's wrong, but I don't know for sure, as Python won't do any calculation at all.  It's easy to enter code and run it, but I can't tell how to get Python to actually DO the calculation.

Any idea what I'm doing wrong?