python - numpy.sort() 错误 ValueError : The truth value of an array with more than one element is ambiguous. 使用 a.any() 或 a.all()

Question

当我使用 numpy 对数组进行排序时这个问题出现了:

Traceback (most recent call last):
File "D:/Desktop/LIP/complier/num/f_t.py", line 75, in <module>
frogs[i].sort(order='length')
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

但是如果我注释掉这些代码，就可以了

        # if len < temp_len:
        #     r_w[i]['length'] = len
        # else:
        #     r_w[i]['points'] = r_g['points']
        #     r_w[i]['length'] = r_g['length']

为什么？

r_g 是最好的路线，r_w 是每组中最差的路线，r_b 是每组中最好的路线。我想循环更改最差的路线 5 次。

代码如下:

# -*- coding: utf-8 -*- 
# __author__ = 'youzipi'
import numpy as np

def cal_length(route):
    length = 0
    for i in range(POINTS_NUM):
        p1 = points[route[i]]
        p2 = points[route[(i + 1) % POINTS_NUM]]
        length += np.linalg.norm(p1 - p2)
    return length

POINTS_NUM = 10
ROUTES_NUM = 50
routetype = np.dtype({
    'names': ['points', 'length'],
    'formats': ['O', 'f']})
routes = np.zeros([(ROUTES_NUM)], dtype=routetype)
points = np.random.rand(POINTS_NUM, 2) * 10
print "points=", points

for index in range(ROUTES_NUM):
    temp = np.random.permutation(range(POINTS_NUM))
    length = cal_length(temp)
    routes[index] = (temp, length)


print "after sort"
routes.sort(order=('length'))
print routes
frogs = np.zeros([5, 10], dtype=routetype)

for i in range(5):
    t = 0
    for j in range(ROUTES_NUM):
        if j%5 == i:
            frogs[i][j/5]['points'] = routes[j]['points']
            frogs[i][j/5]['length'] = routes[j]['length']

for i in range(5):
    print "frogs", i
    print frogs[i]
p = routes['length']
print p
r_g = routes[0]
print "r_g", r_g
r_b = frogs[:, 0]
print "r_b", r_b
r_w = frogs[:, 9]
print "r_w", r_w


#def update_frogs():
#global r_w, r_b, r_b
for i in range(5):
    for j in range(5):
        cut = int(np.random.rand(1)[0] * 10)
        ran = np.random.permutation(range(POINTS_NUM))
        print 'r_w', r_w[i]
        print 'r_b', r_b[i]
        temp_len = r_w[i]['length']
        r_w[i]['points'] = np.hstack((r_b[i]['points'][:cut], np.linspace(-1, -1, 10)[cut:]))
        for t in ran:
            if t not in r_w[i]['points']:
                r_w[i]['points'][cut] = t
                cut = cut + 1
            if cut >= POINTS_NUM:
                break
        len = cal_length(r_w[i]['points'])
        # if len < temp_len:
        #     r_w[i]['length'] = len
        # else:
        #     r_w[i]['points'] = r_g['points']
        #     r_w[i]['length'] = r_g['length']
        frogs[i].sort(order='length')#trackbreak here!!
        r_w[i]['points'] = frogs[i, 9]['points']
        r_w[i]['length'] = frogs[i, 9]['length']
        print "after"
        print 'f_w', r_w[i]
        print 'f_b', r_b[i]

Answer 1

查看“相关”列 - 有很多关于此 ValueError 的问题。

最可能的原因是您生成了一个 True/False 值列表或数组，然后尝试在 Python 中使用它 if/else上下文。

因此，我建议您查看那些问题行中的变量，并确定哪些生成多个值，而不是牵着您的手分析您的所有代码。实际上，因为只有 if声明，它必须是len < temp_len .这两个变量中的其他或其他是数组，而不是标量。

    # if len < temp_len:
    #     r_w[i]['length'] = len
    # else:
    #     r_w[i]['points'] = r_g['points']
    #     r_w[i]['length'] = r_g['length']