squarerootbi.py

# _*_coding:utf-8_*_
#!/usr/bin/env python

# define a function which can compute the squareroot of the number

def squarerootbi(number, epsilon):
    """
    利用二分法计算给定数字和精度的近似平方根
    :rtype: float
    :param number:给定的数字
    :param epsilon:要求的平方根的精确度
    :return:返回给定数字和精度的平方根
    """
    assert number > 0, 'number must > 0' + str(number)
    assert epsilon > 0, 'epsilon must > 0' + str(epsilon)

    # high = number 假设给定数的平方根在0-数字本身之间,然而小数并不是这样
    high = max(number, 1)
    low = 0
    count = 0
    guess = (high + low) / 2.0

    while (abs(guess ** 2 - number) > epsilon) and count <= 100:
        if guess ** 2 > number:
            high = guess
        elif guess ** 2 < number:
            low = guess
        guess = (high + low) / 2.0
        count += 1

    assert count <= 100, 'iter up to 100 the counter is:' + str(count)

    print 'the squareroot of this number is: ' + str(guess) + '       ' + 'count:' + str(count)

def testsuqarerootbi():
    squarerootbi(9, 0.00000000001)
    # squarerootbi(-1, 0.001)
    # squarerootbi(1, -0.1)
    squarerootbi(9, 0.00000001)
    squarerootbi(0.25, 0.0000001)

testsuqarerootbi()

# 使用函数来测试,而不是每次都调用测试对象,可以减少重复