I am working with (lists of) lists of numpy arrays. As a bare bones example, consider this piece of code:
a = [np.zeros(5)]
b = a.copy()
b[0] += 1
Here, I copy a list of one array from a to b. However, the array itself is not copied, so:
print(a)
print(b)
both give [array([1., 1., 1., 1., 1.])]. If I want to make a copy of the array as well, I could do something like:
b = [arr.copy() for arr in a]
and a would remain unchanged. This works well for a simple list, but it becomes more complicated when working with nested lists of arrays where the number of arrays in each list is not always the same.
Is there a simple way to copy a multi-level list and every object that it contains without keeping references to the objects in the original list? Basically, I would like to avoid nested loops as well as dealing with the size of each individual sub-list.
You need to use deepcopy.
import numpy as np
import copy
a = [np.zeros(5)]
b = copy.deepcopy(a)
b[0] += 1
print(a)
print(b)
Result:
[array([0., 0., 0., 0., 0.])]
[array([1., 1., 1., 1., 1.])]