Python奇怪的添加错误 [英] Python weird addition bug

问题描述

可能重复：

蟒蛇 - 与浮点数的小数位问题

Python浮点平等怪异

在下面的代码中，变量百分比这是一个浮动。我已经设置好if number 达到 10,000 ， percentage 假设是由 .01 。

In the code below I have the variable percentage which is a float. I have it set up so that the if number reaches 10,000, percentage is suppose to go up by .01.

# Tries to find a number that when squared and 5%'ed is still a square.

import math

print("Script has started:\n")

percentage = .1
number = 1
while number != -1:
    number = number + 1
    num_powered = number ** 2
    num_5per = num_powered * percentage
    num_5per_sqrt = math.sqrt(num_5per)
    num_list = list(str(num_5per_sqrt))
    dot_location = num_list.index(".")
    not_zero = 0
    for x in num_list[dot_location + 1:]:
        if x != "0":
            not_zero = 1
            break
    if not_zero == 0:
        print("*********************************")
        print("Map :",number)
        print("Safe-Area :",num_5per_sqrt)
        print("Percentage :",percentage)
        print("*********************************")
        input()

    if number > 10000:
              number = 0
              percentage = percentage + .01
              print(percentage)

输出：

Output:

0.11
0.12
0.13
0.14
0.15000000000000002  # Here is where it goes crazy
0.16000000000000003

推荐答案

从 Python文档

请注意，这是二进制浮点的本质：这不是Python中的错误，也不是代码中的错误（强调我的）。在所有语言中，您都会看到支持您的硬件浮点运算的相同类型的东西（尽管有些语言默认情况下可能不会显示差异，或者在所有输出模式下显示差异）

Note that this is in the very nature of binary floating-point: this is not a bug in Python, and it is not a bug in your code either (emphasis mine). You’ll see the same kind of thing in all languages that support your hardware’s floating-point arithmetic (although some languages may not display the difference by default, or in all output modes)

您应该使用 小数模块。

You should probably use the decimal module.

这篇关于Python奇怪的添加错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！