python数学域错误-sqrt

问题描述

是什么原因引起的问题?

What causes the problem?

from math import sqrt
print "a : "
a = float(raw_input())
print "b : "
b = float(raw_input())
print "c : "
c = float(raw_input())
d = (a + b + c)/2
s = sqrt(d*(d-a)*(d-b)*(d-c))
print "a+b+c =", a, b, c
print "Distr. =", d*2, "Area =", s

错误:

Traceback (most recent call last):
   File "C:/Python27/fájlok/háromszög terület2.py", line 11, in <module>
       s = sqrt(d*(d-a)*(d-b)*(d-c))
ValueError: math domain error

推荐答案

问题是 Heron的问题仅当两个数字的总和大于第三个数字时，公式才有效.您需要明确检查.

The problem is that the Heron's formula holds good only when the sum of the two numbers are greater than the third. You need to check that explicitly.

使用代码来实现此目的的更好方法是使用异常处理

A better way as you are using a code to do that is by using Exception handling

try:
    s = sqrt(d*(d-a)*(d-b)*(d-c))
    print "a+b+c =", a, b, c
    print "Distr. =", d*2, "Area =", s
except ValueError:
    print "Please enter 3 valid sides"

如果您想在没有try阻止的情况下进行操作，可以按照以下方式进行操作

If you want to do it without try block you can do it as

delta = (d*(d-a)*(d-b)*(d-c))
if delta>0:
    s = sqrt(delta)
    print "a+b+c =", a, b, c
    print "Distr. =", d*2, "Area =", s
else:
    print "Please enter 3 valid sides"

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