如果我有一个numpy数组列表,使用remove方法会返回一个值错误。
例如:
import numpy as np
l = [np.array([1,1,1]),np.array([2,2,2]),np.array([3,3,3])]
l.remove(np.array([2,2,2]))
给我会出现一个 ValueError:具有多个元素的数组的真值是模棱两可的。使用 a.any() 或 a.all()。
我似乎无法让 all() 起作用,这不可能吗?
def removearray(L,arr):
ind = 0
size = len(L)
while ind != size and not np.array_equal(L[ind],arr):
ind += 1
if ind != size:
L.pop(ind)
else:
raise ValueError('array not found in list.')
如果你需要更快的速度,那么你可以使用Cython进行优化。
这里是你需要的:
list.pop(1)
更新:
list.pop(list.index(element))
我认为您无法避免遍历列表来查找元素的位置。不用担心,Python会默认使用高效的搜索算法,以最小的代价帮助您找到所需元素。
下面的解决方案使用了列表数组的 list.index(element)
方法。
搜索 numpy.ndarray
需要能够哈希 numpy.ndarray 实例。因此,我们需要实现一个哈希算法。这是相当简单的,虽然所呈现的代码看起来有点长,但大多数行都用于检查边缘情况或添加注释。
您可以将代码复制粘贴到文件中,并从命令行或 PyCharm 作为 SDK 运行它。
你需要知道:
注意:
import numpy as np
def remove(array, arrays):
"""
Remove the `array` from the `list` of `arrays`
Operates inplace on the `list` of `arrays` given
:param array: `np.ndarray`
:param arrays: `list:np.ndarray`
:return: None
"""
assert isinstance(arrays, list), f'Expected a list, got {type(arrays)} instead'
assert isinstance(array, np.ndarray), f'Expected a numpy.ndarray, got {type(array)} instead'
for a in arrays:
assert isinstance(a, np.ndarray), f'Expected a numpy.ndarray instances in arrays, found {type(a)} instead'
# Numpy ndarrays are not hashable by default, so we create
# our own hashing algorithm. The following will do the job ...
def _hash(a):
return hash(a.tobytes())
try:
# We create a list of hashes and search for the index
# of the hash of the array we want to remove.
index = [_hash(a) for a in arrays].index(_hash(array))
except ValueError as e:
# It might be, that the array is not in the list at all.
print(f'Array not in list. Leaving input unchanged.')
else:
# Only in the case of no exception we pop the array
# with the same index/position from the original
# arrays list
arrays.pop(index)
if __name__ == '__main__':
# Let's start with the following arrays as given in the question
arrays = [np.array([1, 1, 1]), np.array([2, 2, 2]), np.array([3, 3, 3])]
print(arrays)
# And remove this array instance from it.
# Note, this is a new instance, so the object id is
# different. Structure and values coincide.
remove(np.array([2, 2, 2]), arrays)
# Let's check the result
print(arrays)
# Let's check, whether our edge case handling works.
remove(np.array([1, 2, 3]), arrays)
您可以运行以下一行代码来获取结果...
import numpy as np
# Your inputs ...
l = [np.array([1, 1, 1]), np.array([2, 2, 2]), np.array([3, 3, 3])]
array_to_remove = np.array([2, 2, 2])
# My result ...
result = [a for a, skip in zip(l, [np.allclose(a, array_to_remove) for a in l]) if not skip]
print(result)
...或者将以下内容复制粘贴到脚本中并进行一些实验。
您需要:
请注意:
import numpy as np
def remove(array, arrays):
"""
Remove the `array` from the `list` of `arrays`
Returns list with remaining arrays by keeping the order.
:param array: `np.ndarray`
:param arrays: `list:np.ndarray`
:return: `list:np.ndarray`
"""
assert isinstance(arrays, list), f'Expected a list, got {type(arrays)} instead'
assert isinstance(array, np.ndarray), f'Expected a numpy.ndarray, got {type(array)} instead'
for a in arrays:
assert isinstance(a, np.ndarray), f'Expected a numpy.ndarray instances in arrays, found {type(a)} instead'
# We use np.allclose for comparing arrays, this will work even if there are
# floating point representation differences.
# The idea is to create a boolean mask of the same lenght as the input arrays.
# Then we loop over the arrays-elements and the mask-elements and skip the
# flagged elements
mask = [np.allclose(a, array) for a in arrays]
return [a for a, skip in zip(arrays, mask) if not skip]
if __name__ == '__main__':
# Let's start with the following arrays as given in the question
arrays = [np.array([1, 1, 1]), np.array([2, 2, 2]), np.array([3, 3, 3])]
print(arrays)
# And remove this array instance from it.
# Note, this is a new instance, so the object id is
# different. Structure and values coincide.
_arrays = remove(np.array([2, 2, 2]), arrays)
# Let's check the result
print(_arrays)
# Let's check, whether our edge case handling works.
print(arrays)
_arrays = remove(np.array([1, 2, 3]), arrays)
print(_arrays)
list
作为变量并不是一个好主意,因为它是 Python 中的关键字。这可能会在以后给你带来麻烦。 - Justin Peel