My solution for Drivy dontclickhere riddle

dontclickhere_drivy.py

#!/usr/bin/env python

import sys
from StringIO import StringIO
import requests
from PIL import Image

BASE_URL = 'http://dontclickhere.drivy.com'
CACHE = {}

BIT_COLOR_MAPPING = {
  # Mapping of RGB color tuples to the binary value associated.
  # Coming in 2 different flavors: for RGB and RGBA images.
  'RGB': {
    (238, 46, 129): 0,
    (51, 131, 196): 1,
  },
  'RGBA': {
    (51, 131, 196): 0,
    (53, 132, 197): 1,
  }
}

def img2slices(image, slices):
  """Takes an Image object and returns a list of smaller 
  Image objects sliced from it, vertically.

  Keyword arguments:
  image -- An Image object
  slices -- An integer on how many slices we want (vertically)
  """
  width, height = image.size
  for slice_index in range(slices):
    slice_width = width // slices
    box = (
      slice_width * slice_index, 0,
      slice_width * (slice_index + 1), height
    )
    yield image.crop(box)

def img2byte(image):
  """Takes an Image object and returns a byte in the form of a list
  of 8 binary numbers.

  Keyword arguments:
  image -- An Image object
  """
  slices = img2slices(image, 8)
  for slice in slices:
    sample = tuple(slice.quantize(colors=2, method=2).getpalette()[3:6])
    yield BIT_COLOR_MAPPING[image.mode][sample]

def byte2char(byte):
  """Convert a byte in the form of a list of binary numbers to
  its ASCII char value.

  Keyword arguments:
  byte -- A list of 8 binary numbers, forming together a byte
  """
  return chr(int(''.join(map(str, byte)), 2))

def main():
  i = 0

  while True:
    url = '%s/img/img%d.png' % (BASE_URL, i)
    res = requests.head(url)

    if res.status_code != 200:
      break

    tag = res.headers['ETag']
    if tag in CACHE:
      char = CACHE[tag]
    else:
      res = requests.get(url)
      image = Image.open(StringIO(res.content))
      char = byte2char(img2byte(image))
      CACHE[tag] = char

    sys.stdout.write(char)
    i += 1

if __name__ == "__main__":
  main()