speed bf interpreter (14 minutes)

bf.py

# 18:56
# 19:10

import sys

def do_loops(code):
	loopstack = []
	loops = {}
	for i, char in enumerate(code):
		if char == "[":
			loopstack.append(i)
		elif char == "]":
			i2 = loopstack.pop()
			loops[i] = i2
			loops[i2] = i
	return loops

def brainfuck(code, inputstr):
	loops = do_loops(code)
	i = 0
	pointer = 0
	world = {}
	output = ""
	
	while (i<len(code)):
		char = code[i]
		if char == ".":
			output += chr(world[pointer]) if pointer in world else chr(0)
		elif char == ",":
			if inputstr:
				world[pointer] = ord(inputstr[0])
				inputstr = inputstr[1:]
			else:
				world[pointer] = 0
		elif char == "+":
			world[pointer] = (world[pointer]+1)%256 if pointer in world else 1
		elif char == "-":
			world[pointer] = (world[pointer]-1)%256 if pointer in world else 255
		elif char == "<":
			pointer -= 1
		elif char == ">":
			pointer += 1
		elif char == "[":
			if pointer in world and world[pointer] == 0:
				i = loops[i]
				continue
		elif char == "]":
			if pointer in world and world[pointer] != 0:
				i = loops[i]
				continue
		i += 1
		
	return output

if __name__ == "__main__":
	print(brainfuck(sys.argv[1], sys.argv[2]))