嵌套列表中使用递归的绝对值

Question

I have this nested list:

list1 = [2,-6, [8,-12,-12, [4, [-6], -3]], 7, [3.55, -3.55]].

And I have to use recursion to get absolute values of all elements from the lists so output stays as a list:

[2, 6, [8, 12, 12, [4, [6], 3]], 7, [3.55, 3.55]].

This is the code:

def rec_abs(a):
    new_list=[]
    for el in a:
        if isinstance(el, list):
            new_list.append(rek_abs(el))
        else:
            new_list.append(el)

    return new_list

print(rek_abs([2,-6, [8,-12,-12, [4, [-6], -3]], 7, [3.55, -3.55]]))

Can You give me some tips to solve it (I dont expect full solultion, just some tips)?

Thank You a lot!

Answer 1

Everything is perfect, just use abs() to convert it into absolute value

Note : You have typo in code as rec_abs and rek_abs, which I modified it in below code

def rec_abs(a):
    new_list=[]
    for el in a:
        if isinstance(el, list):
            new_list.append(rec_abs(el))
        else:
            new_list.append(abs(el))
    return new_list

print(rec_abs([2,-6, [8,-12,-12, [4, [-6], -3]], 7, [3.55, -3.55]]))

[2, 6, [8, 12, 12, [4, [6], 3]], 7, [3.55, 3.55]]

Answer 2

For reference, modifying the list in-place is a simple, more efficient alternative, so you should consider this whenever possible. When iterating, iterate over the indices, and assign the return value to the ith index.

def rec_abs(a):
    for i, el in enumerate(a):
        a[i] = rec_abs(el) if isinstance(el, list) else abs(a[i])

    return a

lst = [2,-6, [8,-12,-12, [4, [-6], -3]], 7, [3.55, -3.55]]

print(rec_abs(lst))
[2, 6, [8, 12, 12, [4, [6], 3]], 7, [3.55, 3.55]]