Python/ Using Newtons Method to guess a square root

def square_root(a):
    if a <= 8:
        x = 3
    else:
        x = float(((a/2)/2)/2)
    epsilon = 0.0000001
    while True:
        y = (x +a/x) / 2.0
        if abs(y-x) < epsilon:
            break
        x = y
    print ""
    print "My guess is that the square root of",a,"is",y
""" Guesses square root of 'a' based upon Newtons method which uses
y = (x +a/x) / 2
then repeats with x=y until y and x even out
"""