How to remove multiple elements from a list of lists?

Question

I have list of list elements. In my case, I am using dlib tracker. Appending all detected tracker to a list. I am trying to remove some of the tracker from the list. To make it simple, I have a list like below,

[[1, 2, 3], [4,5,6], [7, 8,9], [2,54,23], [4,12,5], [3,2,6]]

I want to remove list item whenever I found 4 in the list.

For that I used below snippet to find the index to remove elements.

t=  [[1, 2, 3], [4,5,6], [7, 8,9], [2,54,23], [4,12,5], [3,2,6]]
del_item = []
idx = 0
for item in t:
    if 4 in item:
        del_item.append(idx)
    idx+=1
print(del_item)

So far good. I have index of elements to be deleted. I am stuck at how to delete multiple indexes in list of list?

Expected output:

[[1, 2, 3], [7, 8,9], [2,54,23], [3,2,6]]

Answer 1

You can do it simply with one line using list comprehension:

trackers = [[1, 2, 3], [4,5,6], [7, 8,9], [2,54,23], [4,12,5], [3,2,6]]
filtered = [x for x in trackers if 4 not in x]
print(filtered)

Output:

[[1, 2, 3], [7, 8,9], [2,54,23], [3,2,6]]

Answer 2

This task might be done using list comprehension (as already shown) or using filter :

t = [[1, 2, 3], [4,5,6], [7, 8,9], [2,54,23], [4,12,5], [3,2,6]]
tclean = list(filter(lambda x:4 not in x, t))
print(tclean)  # [[1, 2, 3], [7, 8, 9], [2, 54, 23], [3, 2, 6]]

To use filter you need function - in this case I used lambda to make nameless function, though normal function might be used too. filter return iterable so I used list on it to get list.