lights.py

import re

board = [[0 for x in xrange(1000)] for x in xrange(1000)]
on_off = re.compile(r'(toggle|turn on|turn off) ([0-9]+),([0-9]+) through ([0-9]+),([0-9]+)')


def count_on(board):
    return sum([sum(row) for row in board])

def toggle(v):
    if v == 1:
        return 0
    return 1

def do_line(line):
    m = on_off.match(line)
    if m:
        action = m.group(1)
        if action == 'turn on':
            val = lambda x: 1
        elif action == 'turn off':
            val = lambda x: 0
        else:
            val = toggle
        start_x = int(m.group(2))
        start_y = int(m.group(3))
        end_x = int(m.group(4)) + 1
        end_y = int(m.group(5)) + 1
        for x in range(start_x, end_x):
            for y in range(start_y, end_y):
                # print('{},{}'.format(x,y))
                board[x][y] = val(board[x][y])


do_line('turn on 0,0 through 999,999')
assert count_on(board) == 1000000
do_line('toggle 0,0 through 999,0')
assert count_on(board) == 999000

do_line('turn on 0,0 through 999,999')
assert count_on(board) == 1000000
do_line('turn off 499,499 through 500,500')
assert count_on(board) == 999996

# reset board
do_line('turn off 0,0 through 999,999')
with open('inst.txt') as f:
    for l in f:
        do_line(l)
print(count_on(board))