检查数组是否是数组列表的元素

I have 13 python NumPy arrays:

我有13个python NumPy数组:

obj_1=np.array([784,785,786,787,788,789,790,791,792])
obj_2=np.array([716,717,718,730,731,732,721,722,724,726,727])
obj_3=np.array([658,659,660,661,662,663,664,665])
obj_4=np.array([581,582,583,589,590,591,595,597,598,599,601,605,606,613,614])
obj_5=np.array([533,534,535,536,537])
obj_6=np.array([464,469,472,474])
obj_7=np.array([406,409,411,412])
obj_8=np.array([345,346,347,349])
obj_9=np.array([277,278,281,282,283,284,288,296])
obj_10=np.array([217,219,220,223,224])
obj_11=np.array([154,155,156,157,158,159,160,161])
obj_12=np.array([91,92,93,94,95,96,97])
obj_13=np.array([28,29,30,31,32,33,34])

Then the following loop:

然后是以下循环:

for i in [obj_1, obj_2, obj_3, obj_4, obj_5, obj_6, obj_7, obj_8, obj_9, obj_10, obj_11, obj_12, obj_13]:
    print i in [obj_1, obj_2, obj_3, obj_4, obj_5, obj_6, obj_7, obj_8, obj_9]

I would expect this output:

我希望这个输出:

True
True
True
True
True
True
True
True
True
False
False
False
False

Instead I get the following with an error:

相反,我得到以下错误:

True
True
True
True
True
True
Traceback (most recent call last):

File "<ipython-input-221-c03c1ef308c6>", line 16, in <module>
print i in [obj_1, obj_2, obj_3, obj_4, obj_5, obj_6, obj_7, obj_8, obj_9]

ValueError: The truth value of an array with more than one element is ambiguous. Use  a.any() or a.all()

I tested different arrays with the same names and the same for loop; they produced no error.

我测试了不同的数组,它们具有相同的名称和相同的循环;他们没有产生错误。

It seems like the problem lies in the content of the arrays, but I couldn't figure out where.

似乎问题在于数组的内容,但我无法弄清楚在哪里。

Does anyone have an idea why this happens?

有谁知道为什么会这样?

1 个解决方案

#1

When you do obj in list python compares obj for equality with each of the members of list. The problem is that the equality operator in numpy doesn't behave in a consistent way. For example:

当您在列表中执行obj时,python将obj与列表中的每个成员进行相等性比较。问题是numpy中的相等运算符的行为不一致。例如:

>>> obj_3 == obj_6
False

because they have different lengths, a boolean is returned.

因为它们有不同的长度,所以返回一个布尔值。

>>> obj_7==obj_6
array([False, False, False, False], dtype=bool)

because they have the same length, the arrays are compared element wise and a numpy array is returned. In this case the truth value is undetermined. It looks like this strange behaviour is going to change in the future.

因为它们具有相同的长度,所以将数组进行元素比较并返回numpy数组。在这种情况下,真值是不确定的。看起来这种奇怪的行为将来会发生变化。

The correct way to do it would be to compare individually each pair of arrays using for example numpy.array_equal:

正确的方法是使用例如numpy.array_equal单独比较每对数组:

for i in [obj_1, obj_2, obj_3, obj_4, obj_5, obj_6, obj_7, obj_8, obj_9, obj_10, obj_11, obj_12, obj_13]:
    print any(np.array_equal(i, j) for j in [obj_1, obj_2, obj_3, obj_4, obj_5, obj_6, obj_7, obj_8, obj_9])

gets you:

True
True
True
True
True
True
True
True
True
False
False
False
False

#1