比较 3 个位置之间的距离，但结果不可靠

Question

我正在尝试创建一个代码来计算 2 点之间的距离。我有 3 个点（Point1、Point2 和 Point3），我想比较每个点组合（1 vs 2、1 vs 3 和 2 vs 3）并找出哪个组合与预期结果的距离最长：

The distance between PointX and PointY is the longest, with distance {distance_XY}

我使用的代码是：

def longest_distance(X,Y,Z):
  a = X[0]
  b = X[1]
  c = Y[0]
  d = Y[1]
  e = Z[0]
  f = Z[1]
  distance_XY = (((a-c)**2) + ((b-d)**2)) ** (1/2)
  distance_XZ = (((a-e)**2) + ((b-f)**2)) ** (1/2)
  distance_YZ = (((c-e)**2) + ((d-f)**2)) ** (1/2)
  if distance_XY > distance_XZ > distance_YZ:
    print(f'The distance between PointX and PointY is the longest, with distance {distance_XY}')
  elif distance_XY < distance_XZ > distance_YZ:
    print(f'The distance between PointX and PointZ is the longest, with distance {distance_XZ}')
  elif distance_XY < distance_XZ < distance_YZ:
    print(f'The distance between PointY and PointZ is the longest, with distance {distance_YZ}')

但该代码仅适用于某些数字。当我尝试使用下面的数字时，它起作用了：

X = [0,0]
Y = [5,5]
Z = [10,10]

longest_distance(X,Y,Z)

The distance between PointX and PointZ is the longest, with distance 14.142135623730951

当我尝试使用不同的数字时：

X = [0,0]
Y = [10,-10]
Z = [4,-3]

longest_distance(X,Y,Z)

结果应该是The distance between PointX and PointY is the longest, with distance 14.142135623730951，但是什么也没发生，也没有错误，所以我真的不知道如何更正它

Answer 1

没有任何反应，因为 None 您设置的条件得到满足。使用您的输入时：

X = [0,0]
Y = [10,-10]
Z = [4,-3]

发生的事情是：

distance_XY = 14.14213...

distance_XZ = 5.0

distance_YZ = 9.219544...

我们可以清楚地看到 'distance_XY' 是最大的，但是三个条件都为 False 因为： 14.14213... > 5.0 < 9.219544

因此您没有得到任何印刷品。放置 else: 是一个很好的做法，然后写一个一般说明，说明满足 none 个条件。

不过，我会尝试通过执行以下操作来检查最大值：

max_val = max(distance_XY, distance_XZ, distance_YZ)
if distance_XY == max_val:
    print(f'The distance between PointX and PointY is the longest, with distance {distance_XY}')
elif distance_XZ == max_val:
    print(f'The distance between PointX and PointZ is the longest, with distance {distance_XZ}')
elif distance_YZ == max_val:
    print(f'The distance between PointY and PointZ is the longest, with distance {distance_YZ}')
else:
    print('None of the conditions were met, something went wrong')

Answer 2

您正在寻找三个值中的最大值，但您要检查的是顺序。在你的第二个例子中：

distance_XY, distance_XZ, distance_YZ = 14.142135623730951 5.0 9.219544457292887.

这意味着您的第一个条件应该为真。但它不是，因为 distance_XY > distance_XZ -> True（没关系），而是 distance_XZ > distance_YZ -> False。所以第二个 > 导致整个条件变为假，即使这不相关，因为 distance_XY 是最大值。

尝试以不同方式定义您的条件以获得最大距离。或者使用另一种最大方法。

通常，要调试此类问题，请尝试添加一些打印语句以查看中间值。然后尝试考虑给定这些值会出现什么问题。

对于使用最大值的简洁方法，您可以执行以下操作：

def longest_distance(X, Y, Z):
    (a, b), (c, d), (e, f) = X, Y, Z

    distances = {("X", "Y"): (((a-c)**2) + ((b-d)**2)) ** (1/2),
                 ("X", "Z"): (((a-e)**2) + ((b-f)**2)) ** (1/2),
                 ("Y", "Z"): (((c-e)**2) + ((d-f)**2)) ** (1/2)}

    (max_name_x, max_name_y), max_value = max(distances.items(),
                                              key=lambda x: x[1])
    
    print(f'The distance between Point{max_name_x} and Point{max_name_y} '
          f'is the longest, with distance {max_value}')

比较 3 个位置之间的距离，但结果不可靠

Compare distance between 3 location but the results are not reliable

python

if-statement

function