light_switches.py

#!/bin/python

switchFile = 'switches.txt'

with open(switchFile, 'r') as f:
    lines = f.readlines()

numSwitch = int(lines[0])

switches = range(0, numSwitch)

switchGrid = {switch: 'off' for switch in switches}

def getrange(l):
    x, y = [int(x) for x in l.split()]
    if y > x:
        return range(x, y)
    else:
        return range(y, x)

r = map(getrange, lines[1:])

for x in r:
    for i in list(x):
        if switchGrid[i] == 'off':
            switchGrid[i] = 'on'
        else:
            switchGrid[i] = 'off'

def countSwitch():
    onswitch = 0
    for i in switchGrid:
        if switchGrid[i] == 'on':
            onswitch += 1
    print(onswitch)

countSwitch()