Question

以下是我的代码的一部分：

students = 0
weight = 0
height = 0

while students < 5:
    name = input("Please enter the name. ")
    students = students + 1

while weight == 0:
    try:
        weight = float(input("Please enter the weight in kgs "))

        if weight <= 0:
            print ("Please enter a number greater than zero ")
            weight = 0
            continue

    except ValueError:
        print ("No number found, please enter a number greater than zero ")
        weight = 0
        continue

while height == 0:
    try:
        height = float(input("Please enter the height in metres "))


        if height <= 0:
            print ("Please enter a number greater than zero ")
            height = 0
            continue

    except ValueError:
        print ("No number found, please enter a number greater than zero ")
        height = 0
        continue

BMI = (weight/(height*height))
print (name, "has the BMI of", "%.2f" %BMI)
if BMI < 18.5:
    print ("The student is underweight.")
elif 18.5 <= BMI <= 27:
    print ("The student is a healthy weight.")
elif BMI > 27:
    print ("The student is overweight.")

weight = 0
height = 0

然而，当BMI为18.5时，它表示学生体重不足，当BMI为27时，表示学生超重，两者实际上都应该是健康体重？例如体重53.456和身高1.7米显示体重不足

Answer 1

>>> 53.456/(1.7*1.7)
18.496885813148793
>>> 53.456/(1.7*1.7) <= 18
False

我觉得它只是浮点错误，试试

>>> round(53.456/(1.7*1.7), 2)
18.5
>>> round(53.456/(1.7*1.7), 2) <= 18.5
True

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Answer 2

一般来说，浮点数不准确，因为它们在计算机中的表现方式。它们只是非常接近的近似值。因此，测试与浮点数的精确相等必然会导致挫败感。您可能应该关闭数字或不测试相等性。

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Answer 3

浮点数仅近似十进制数。你的比较可能会超过/低于你的乘法或除法的顺序或一天的时间......不完全。如果您想要进行有意义的相等比较，那么请查看python中的decimal库。您可以将精度设置为两位小数，突然您的比较和计算器数学应该有效。

浮点计算和控制流程

3 个答案: