solution.py

def parse(line, data):
  incom, outName = line.split(" -> ")
  tokens = incom.split(" ")
  if len(tokens) == 1:
    try:
      val = int(tokens[0])
      data[outName] = val
    except Exception:
      data[outName] = tokens[0]
  elif len(tokens) == 2:
    data[outName] = (tokens[1], lambda x: ~x)
  elif len(tokens) == 3:
    a, op, b = tokens[:3]
    if op == "AND":
      try:
        val = int(tokens[0])
        data[outName] = (b, lambda x: val & x)
      except Exception:
        data[outName] = (a, b, lambda x, y: x & y)
    elif op == "OR":
      data[outName] = (a, b, lambda x, y: x ^ y)
    elif op == "RSHIFT":
      num = int(b)
      data[outName] = (a, lambda x: x >> num)
    elif op == "LSHIFT":
      num = int(b)
      data[outName] = (a, lambda x: x << num)


def connect(out, data, computed):
  if out in computed:
    return computed[out]

  incom = data[out]
  if type(incom) is int:
    computed[out] = incom
    return incom
  elif type(incom) is not tuple:
    computed[out] = connect(incom, data, computed)
    return computed[out]
  elif len(incom) == 2:
    a = connect(incom[0], data, computed)
    computed[out] = incom[1](a)
    return computed[out]
  elif len(incom) == 3:
    a = connect(incom[0], data, computed)
    b = connect(incom[1], data, computed)
    computed[out] = incom[2](a, b)
    return computed[out]

lines = open("day7.input").read().split("\n")
data = {}
map(lambda l: parse(l, data), lines)
print connect("a", data, {})