Stuck with using lists to solve task

[perfringo]

If using 0 and 1 to represent closed / open doors it's simple to toggle value using XOR (bitwise exclusive OR). Something along those lines (just an idea, haven't tested it):

# 1 means door open, 0 mean doors closed
# create list of 100 doors open
doors = [1] * 100

# toggle every second value
for i in range(1, 100, 2):
     doors[i] ^= True

# toggle nth value with nth step
for n in range(2, 101):
    for i in range(n, 100, n):
        doors[i] ^= True

print(doors)
print(sum(doors))