递归遍历python中的列表

Question

In a learning exercise we were asked to traverse a multi-dimensional list and print all of its values in a single function/for loop.

My brain got stuck on the basics of how a recursive function should work, through some online examples I came up with what I tought was the answer, but it stops at the first list with values it finds.

What was the mistake of my train of tought here?

def walk(l):
    for v in l:
        if type(v) is list:
            return walk(v)
        else:
            print(v)

l = [

    [1,2,3],
    [4,5,6],
    [7,8,9]
]

walk(l)

>>1
>>2
>>3

Answer 1

Remove the return statement, as it stops you from going into the next iteration in the for loop (when you call walk(l) , it checks the first sub list and finds that it is a list and then encounter return, this stops the execution of the current function and so it will not go to the next iteration any more but will only execute walk([1,2,3]) and print out the results):

def walk(l):
    for v in l:
        if type(v) is list:
            walk(v)
        else:
            print(v)

walk(l)
1
2
3
4
5
6
7
8
9