Python 在 NumPy 数组中查找等于零的元素的索引
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Find indices of elements equal to zero in a NumPy array
提问by gotgenes
采纳答案by mtrw
numpy.where()is my favorite.
numpy.where()是我的最爱。
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.where(x == 0)[0]
array([1, 3, 5])
回答by nate c
You can search for any scalar condition with:
您可以使用以下命令搜索任何标量条件：
>>> a = np.asarray([0,1,2,3,4])
>>> a == 0 # or whatver
array([ True, False, False, False, False], dtype=bool)
Which will give back the array as an boolean mask of the condition.
这将返回数组作为条件的布尔掩码。
回答by dvdvck
If you are working with a one-dimensional array there is a syntactic sugar:
如果您正在使用一维数组，则有一个语法糖：
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> numpy.flatnonzero(x == 0)
array([1, 3, 5])
回答by Dusch
You can also use nonzero()by using it on a boolean mask of the condition, because Falseis also a kind of zero.
您也可以nonzero()在条件的布尔掩码上使用它，因为False它也是一种零。
>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8])
>>> x==0
array([False, True, False, True, False, True, False, False, False, False, False], dtype=bool)
>>> numpy.nonzero(x==0)[0]
array([1, 3, 5])
It's doing exactly the same as mtrw's way, but it is more related to the question ;)
它的做法与mtrw's 的方式完全相同，但与问题更相关；)
回答by sramij
import numpy as np
x = np.array([1,0,2,3,6])
non_zero_arr = np.extract(x>0,x)
min_index = np.amin(non_zero_arr)
min_value = np.argmin(non_zero_arr)
回答by MSeifert
There is np.argwhere,
import numpy as np
arr = np.array([[1,2,3], [0, 1, 0], [7, 0, 2]])
np.argwhere(arr == 0)
which returns all found indices as rows:
它将所有找到的索引作为行返回：
array([[1, 0], # Indices of the first zero
[1, 2], # Indices of the second zero
[2, 1]], # Indices of the third zero
dtype=int64)
回答by Jeril
I would do it the following way:
我会这样做：
>>> x = np.array([[1,0,0], [0,2,0], [1,1,0]])
>>> x
array([[1, 0, 0],
[0, 2, 0],
[1, 1, 0]])
>>> np.nonzero(x)
(array([0, 1, 2, 2]), array([0, 1, 0, 1]))
# if you want it in coordinates
>>> x[np.nonzero(x)]
array([1, 2, 1, 1])
>>> np.transpose(np.nonzero(x))
array([[0, 0],
[1, 1],
[2, 0],
[2, 1])
回答by chmnsk
You can use numpy.nonzero to find zero.
您可以使用 numpy.nonzero 来查找零。
>>> import numpy as np
>>> x = np.array([1,0,2,0,3,0,0,4,0,5,0,6]).reshape(4, 3)
>>> np.nonzero(x==0) # this is what you want
(array([0, 1, 1, 2, 2, 3]), array([1, 0, 2, 0, 2, 1]))
>>> np.nonzero(x)
(array([0, 0, 1, 2, 3, 3]), array([0, 2, 1, 1, 0, 2]))
