Remove invalid entries in nested list [duplicate]

Question

I am still a bit of a beginner, and I can't figure out a good way to crack this nut.

I have a nested list of arbitrary depth. Something like :

sample = [[1, [2, '', [None, 5], [6]]], None]

I need to cycle through each level of the list and remove any entries that are empty strings or None. Aside from this, the nested list should be unchanged.

I suspect something like recursion, but I've never created a function that does that, nor can I find a good example online that fits my needs. My attempts have been utterly ineffective.

Any help would be appreciated, as I am at a bit of a loss how to even start.

Answer 1

def filter_null(l):
    l = l.copy()
    i = 0
    while i < len(l):
        if isinstance(l[i], list):
            l[i]= filter_null(item) # this is the recursion
        if not item: # Checks if item evaluates to False or None
            l.pop(i)
            i -= 1 # If you delete this line the following item will be skipped
        i += 1

Answer 2

You can use recursion:

sample = [[1, [2, '', [None, 5], [6]]], None] 
def rem_vals(r):
   return [rem_vals(i) if isinstance(i, list) else i for i in r if i not in [None, '']]

print(rem_vals(sample))

Output:

[[1, [2, [5], [6]]]]