Need help with sum_light task

Hello people!

Would be grateful for help.

Trying to solve sum_light task, but encountered with exception: TypeError: 'str' object cannot be interpreted as an integer

Code passes assertions from the task but fails after Check Solution.

Could you tell me where I've mistaken or should I take another direction in solution:

from datetime import datetime from typing import List import operator

def sumlight(els: List[datetime]) -> int: bulbswitchedon = els[1::2] bulbswitchedoff = els[::2] timedelta = [bulbeon - bulbeoff for bulbeon, bulbeoff in zip(bulbswitchedon, bulbswitchedoff)] seconds = timedelta[0].totalseconds()

#variable for incrementing datetime.timedelta items to recieve sum
b = time_delta[0] - time_delta[0]

if len(time_delta) > 1 and len(time_delta) < 3:
    first_range = time_delta[1::2]
    second_range = time_delta[::2]
    p = [abs(first + second) for first, second in zip(first_range, second_range)]
    another_seconds = p[0].total_seconds()
    return another_seconds

elif len(time_delta) >= 3:
    for a in time_delta:
        b += a
        seconds = b.total_seconds()
    return seconds

return seconds

Thank you!