brainfuck.py

def setup():
  index = 0
  vals = []
  for i in range(256):
    vals.append(0)
  program = raw_input('enter your brainfuck program: ')
  parens = match_parens(program)
  interpret(vals,index,parens,program)

def interpret(vals,index,parens,program):
  i = 0
  ivparens = {v: k for k, v in parens.items()}
  while i < len(program):
    if program[i] == '>':
      index=index+1
    elif program[i] == '<':
      index=index-1
    elif program[i] == '+':
      vals[index]=vals[index]+1
    elif program[i] == '-':
      vals[index]=vals[index]-1
    elif program[i] == '[':
      if vals[index] == 0:
        i = parens[i]
    elif program[i] == ']':
      if vals[index] != 0:
        i = ivparens[i]
    elif program[i] == '.':
      print chr(vals[index])
    elif program[i] == ',':
      vals[index] = ord(raw_input()[0])
    i=i+1

def match_parens(program):
  stack = []
  parens = {}
  for i in range(len(program)):
    if program[i] == '[':
      stack.append(i)
    if program[i] == ']':
      parens.update({stack.pop(): i})
  return parens

setup()