Fixed Iteration method

# Fixed iteration method to find approximate root
from math import sqrt
#function definition
def f(x):
    f1=1.0/sqrt(1+x)
    return f1

e=0.0001
x0=float(input("Enter starting value   "))

while abs(f(x0)-x0)>=e:
    x0=f(x0)
  
  
print 'The best approximation to root is %.4f'%(x0)