你能解释一下双端队列中这个奇怪的 "updating" of np.array 内容吗？

Question

这段代码好像"update"一个双端队列里面的内容？例如

import numpy as np
from collections import deque

buffer = deque()
load = np.array([1])

for loop in range(5):     
    print(list(buffer))  
    print("   >>>>> load[0] = loop # .... ...")
    load[0] = loop
    print(list(buffer))              
    print("   >>>>> buffer.append ...")
    buffer.append([loop, load])

输出=

[]
   >>>>> load[0] = loop # .... ...
[]
   >>>>> buffer.append ...
[[0, array([0])]]
   >>>>> load[0] = loop # .... ...
[[0, array([1])]]
   >>>>> buffer.append ...
[[0, array([1])], [1, array([1])]]
   >>>>> load[0] = loop # .... ...
[[0, array([2])], [1, array([2])]]
   >>>>> buffer.append ...
[[0, array([2])], [1, array([2])], [2, array([2])]]
   >>>>> load[0] = loop # .... ...
[[0, array([3])], [1, array([3])], [2, array([3])]]
   >>>>> buffer.append ...
[[0, array([3])], [1, array([3])], [2, array([3])], [3, array([3])]]
   >>>>> load[0] = loop # .... ...
[[0, array([4])], [1, array([4])], [2, array([4])], [3, array([4])]]
   >>>>> buffer.append ...

...如你所见，当数组被赋予新值时，双端队列中的数组内容被更新 ?

Answer 1

deque持有一个reference单单。您附加到 buffer 的每个元素都指向相同的 np.array，最初名为 load.

Answer 2

您的代码中只有一个 load 对象，您的双端队列中的每一项都引用同一个对象。如果您希望它们不同，请在每个循环中创建一个新的：

import numpy as np
from collections import deque

buffer = deque()


for loop in range(5):     
    print(list(buffer))  
    print("   >>>>> load[0] = loop # .... ...")
    load = np.array([loop])
    print(list(buffer))              
    print("   >>>>> buffer.append ...")
    buffer.append([loop, load])

输出：

[]
   >>>>> load[0] = loop # .... ...
[]
   >>>>> buffer.append ...
[[0, array([0])]]
   >>>>> load[0] = loop # .... ...
[[0, array([0])]]
   >>>>> buffer.append ...
[[0, array([0])], [1, array([1])]]
   >>>>> load[0] = loop # .... ...
[[0, array([0])], [1, array([1])]]
   >>>>> buffer.append ...
[[0, array([0])], [1, array([1])], [2, array([2])]]
   >>>>> load[0] = loop # .... ...
[[0, array([0])], [1, array([1])], [2, array([2])]]
   >>>>> buffer.append ...
[[0, array([0])], [1, array([1])], [2, array([2])], [3, array([3])]]
   >>>>> load[0] = loop # .... ...
[[0, array([0])], [1, array([1])], [2, array([2])], [3, array([3])]]
   >>>>> buffer.append ...

你能解释一下双端队列中这个奇怪的 "updating" of np.array 内容吗？

Can you explan this weird "updating" of np.array content inside a deque?

python

arrays

numpy

deque