npv

%matplotlib qt4

%matplotlib inline

import scipy as sp

from matplotlib.pyplot import *

cashflows=[-100,50,60,70]

rate=[]

npv=[]

x=(0,0.7)

y=(0,0)

for i in range(1,70):

 rate.append(0.01*i)

 npv.append(sp.npv(0.01*i,cashflows[1:])+cashflows[0])

plot(rate,npv),plot(x,y)

show()