I have a double nested list. I would like to remove the second element inside of the nested list. i.e. [[[x,1],[x,2],[x,3]],[[x,1],[x,2],[x,3]]]

Question

for x in y:
    [z.pop(0) for z in x]

IndexError: pop index out of range.

The function seems to keep looping after it has gone through all the values of x. I would like to move on the next value of x after it has done it has completed its work. I understand that the error is occurring due to the changing of my data shape, but how do I avoid this?

Answer 1

First solution:

nested_list = [[[11,1],[20,2],[300,3]],[[100,1],[202,2],[303,3]]]
for lst in nested_list:
    for j in lst:
        j.pop(1)
print(nested_list)

The above solution will give you the following output:

[[[11], [20], [300]], [[100], [202], [303]]]

Second Solution

nested_list = [[[11,1],[20,2],[300,3]],[[100,1],[202,2],[303,3]]]
result = []
for lst in nested_list:
    for j in lst:
        result.append(j[0])
print(result)
del nested_list

The above solution will give you the following output:

[11, 20, 300, 100, 202, 303]

If you are familiar with python then you can also go with the following:

nested_list = [[[11,1],[20,2],[300,3]],[[100,1],[202,2],[303,3]]]
def return_first(lst):
    return [j[0] for i in lst for j in i]
print(return_first(nested_list))
del nested_list

The above solution will give you the following output:

[11, 20, 300, 100, 202, 303]