I cannot delete and the elements from the list

[snippsat]

Don't modify an iterator while you're iterating over it,it's a known bad pattern💀
Will mess up list index and will get your result.
Could add enumerate(l2[:]) to make it work,but still no t good as as remove() has to go over the whole list for every iteration O(n^2).

The solution is to make a new list,then therew is no remove()(that rarely ever need to be used) used in the loop.

l2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
a = 1
result = []
for ind, el in enumerate(l2):
    if el != a:
       result.append(el)

print(result)

[0, 2, 3, 4, 5, 6, 7, 8, 9]

Or list comprehension.

>>> l2 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> [el for el in l2 if el != 1]
[0, 2, 3, 4, 5, 6, 7, 8, 9]