我有一段代码，我需要在numpy数组中查找值的索引。 对于此任务，我使用numpy.where。 问题是numpy.where产生错误的结果，即返回一个空数组，在我确定搜索的值在数组中的情况下。 更糟糕的是，我测试了元素是否真的在数组中有一个for循环，如果找到它，也可以用numpy.where查找它。 奇怪的是，它找到了一个结果，而后来确实是一行，它不会。
以下是代码的外观：
# progenitors, descendants and progenitor_outputnrs are 2D-arrays that are filled from reading in files.
# outputnrs is a 1d-array.
ozi = 0
for i in range(descendants[ozi].shape[0]):
if descendants[ozi][i] > 0:
if progenitors[ozi][i] < 0:
oind = outputnrs[0] - progenitor_outputnrs[ozi][i] - 1
print "looking for prog", progenitors[ozi][i], "with outputnr", progenitor_outputnrs[ozi][i], "in", outputnrs[oind]
for p in progenitors[oind]:
if p == -progenitors[ozi][i]:
# the following line works...
print "found", p, np.where(progenitors[oind]==-progenitors[ozi][i])[0][0]
# the following line doesn't!
iind = np.where(progenitors[oind]==-progenitors[ozi][i])[0][0]
我得到了输出：
looking for prog -76 with outputnr 65 in 66
found 76 79
looking for prog -2781 with outputnr 65 in 66
found 2781 161
looking for prog -3797 with outputnr 63 in 64
found 3797 163
looking for prog -3046 with outputnr 65 in 66
found 3046 163
looking for prog -6488 with outputnr 65 in 66
found 6488 306
Traceback (most recent call last):
File "script.py", line 1243, in <module>
main()
File "script.py", line 974, in main
iind = np.where(progenitors[oind]==-progenitors[out][i])[0][0]
IndexError: index 0 is out of bounds for axis 0 with size 0
我使用python 2.7.12和numpy 1.14.2。
有谁知道为什么会这样？