numerical method

from math import atan2

def iterate(ans):
return 0.5*atan2(1,2*ans)

def iterator(ans,x):
if round(iterate(ans),3) != round(ans,3):
    print 'iteration no.',x,'is',iterate(ans)
    iterator(iterate(ans),x+1)

x=2
iterator(0.4,x)


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iteration no. 2 is 0.448027692286
iteration no. 3 is 0.420082425036
iteration no. 4 is 0.436019928837
iteration no. 5 is 0.426822664718
iteration no. 6 is 0.432094882111
iteration no. 7 is 0.429060919042
iteration no. 8 is 0.430802986936
iteration no. 9 is 0.429801433113