import random PV = 4329.48 P = 1000 n = 1 t = 5 m = n*t a = random.random() tol = 0.000001 No = 100 def f(PV,P,m,i): f = (PV/P)*i + (1+i)**(-m)-1. return f def fp(PV,P,m,i): f = -m*(i+1)**(-m-1.)+(PV/P) return f i = 1 while i <= No: p = a-f(PV,P,n,a)/fp(PV,P,n,a) if abs(p-a)<tol: print('success') print('i = ', round(p,2)) break i = i+1 a = p if i>No: print('unsuccess')