返回固定长度的值

Question

我试图用牛顿-拉斐逊方法计算一个数的平方根。这一部分比较直截了当。然而，当我想确保最终答案上返回的值始终是100位小数时，我似乎无法让它工作。我在VS代码和Jupyter笔记本上试过，似乎只能显示到小数点后17或18位

我的代码是：

import decimal as Dec

Dec.getcontext().prec = 100

Number = 5
bStart = 1                                                                  # Start value is 1
zStart = 1                                                                  # Start value is 1 (x0)

aCount = 0                                                                  # Iteration count
yNewNum = 0                                                                 # New value of estimate (x1)
xRoot = 0                                                                   # Used to transfer values between yNewNum and zStart

while aCount < 101:                                                         # While the difference between zStart and yNewNum is greater than 0.0000001 (7 decimal places)
    yNewNum = (zStart + (Number / zStart)) / 2                              # x1 = (x0 + (S/x0)) / 2 
    zStart = yNewNum                                                        # Replace the value x0 with the value of x1
    yNewNum = xRoot                                                         # Replace the value of x1 with the transfer value
    xRoot = zStart                                                          # Replace the transfer value with x0
    aCount += 1                                                             # aCount iterates by 1
    print()
    print(aCount, ":", Dec.Decimal(zStart))
    print(len(str(zStart)))
print("Newton-Raphson method =  ", Dec.Decimal(zStart))
print("Length:", len(str(zStart)))

在两个平台上，当起始值为15时，最后几次迭代的输出如下所示：

98 : 3.87298334620741702138957407441921532154083251953125

Length: 17

99 : 3.87298334620741702138957407441921532154083251953125

Length: 17

100 : 3.87298334620741702138957407441921532154083251953125

Length: 17

101 : 3.87298334620741702138957407441921532154083251953125

Length: 17

Newton-Raphson method =
3.87298334620741702138957407441921532154083251953125

Length: 17

有没有关于如何让小数点显示100位小数的建议？请注意，我必须使用Newton-Raphson方法，因为这是一个要求

Answer 1

在浮点操作中，必须至少使用十进制类型初始化一个变量

您必须使用Number = Dec.Decimal(5)