python 二分求根

#! /usr/bin/python

def my_sqrt(x=0.01):
    if x < 0:
        return 0

    cnt = 0
    if x >1 :
        m = 0
        n = x
        s = (m + n) / 2.0
        while abs(s**2 - x )>= 1e-5:
            cnt += 1
            if ( s**2 < x):
                m = s
                s = (m + n) / 2.0
                print 'm is:', m
            else:
                n = s
                s = (m + n) / 2.0
                print 'n is:', n
        print 'm is', m
        print 'n is', n
        print 'cnt is', cnt
    else:
        m = 0
        n = 1
        mid = (m+n)/2.0

        while abs(mid ** 2 - x) >= 1e-5:
            cnt += 1
            if( mid ** 2 < x):
                m = (m + x)
                mid = (m + n)/2.0
            else:
                n = ( n + x )/2
                mid = (m + n)/2.0

            print m , n, mid, cnt
my_sqrt(01)