如果为空，则在子列表中输入值

Question

So I have a larger for loop which produces nested lists of various of sizes: eg

[[6], [3], [5], [3, 2, 5, 3], [5], [6, 5, 4], [5, 3, 2]]
[[5], [], [], [4], [3]]
[[5], [2]]
[[], [4], [3, 2, 4]

In short, I would like it so that each array that has an empty sublist to simply be the value 0. So like : If the list generated is : [[6], [3], [5], [3, 2, 5, 3], [5], [6, 5, 4], [5, 3, 2]]

Then I would keep it that way.

But if the list generated is: [[5], [], [], [4], [3]]

Then I would like it to be: [[5], [0], [0], [4], [3]]

Likewise, for the final row above, I would want it to be: [[0], [4], [3, 2, 4]

I have been trying something along the lines of :

for k in range(0,len(TempAisle)):
           if TempAisle[k][0] == None:
               TempAisle[k][0]= 0
 k+=1

But I am getting an list index out of range error.

It seems to be a rather simple problem and have seen others who have asked ways to check if there is a sublist that is empty but I am having trouble replacing it with another value (0 in my case). Any help and explanation will be appreciated.

Answer 1

You can iterate on the items directly - the more Pythonic way - no need to use range . Test for the truthiness of each of the items (empty lists are falsy ), and append a zero only if the sublist is empty:

for x in TempAisle:
    if not x:
        x.append(0)

Answer 2

For a one-line solution:

x = [elem or [0] for elem in TempAisle]

An EDIT based on the comment of @Moses Koledoye, to avoid creating a new list, but to keep it as a one-line solution:

[x.append(0) for x in TempAisle if not x]