Python : remove list from list of list

you are modifying a list while you are iterating over it. that will not work as expected.

what you could do is use a list-comprehension:

lst = [item for item in list1 if item[0] != 'Summary']

you could also mutate your current list directly:

list1[:] = [item for item in list1 if item[0] != 'Summary']

After each pop the length of your list changes. So the second pop will have a shorter list and eventually the argument to pop might be to big for the remaining list.

If you need in place modification, you can iterate the list in reverse to prevent this problem:

for i in range(len(list1)-1, -1, -1):
    if list1[i][0] == 'Summary':
        list1.pop(i)

You can even modify list while iterating over the list with comprehension:

list1 = [x for x in list1 if not x[0] == 'Summary']

You can iterate over the items directly and pop via the index method like so:

for l in list1:
    if l[0] == 'Summary':
        list1.pop(list1.index(l))

However, this will not work if there's more than one summary. As others mentioned, this is because the index changes when you pop an item.

Therefore, the best way is to use a list comprehension and create a new list of all the items that aren't the summary. It can even have the same variable name:

list1 = [item for item in list1 if item[0] != 'Summary']