Brainf*ck interpreter

bf.py

#!/usr/bin/python

from __future__ import print_function
import sys

if len(sys.argv) > 1:
    with open(sys.argv[1]) as src:
        program = src.read()
else:
    print("No input file.")
    sys.exit(0)

inst_ptr = 0
data_ptr = 0
data = [0 for i in range(30000)]
inst = program[0]

while len(program) > inst_ptr:
    inst = program[inst_ptr]

    if inst == '>':
        data_ptr += 1
    elif inst == '<':
        data_ptr -= 1
    elif inst == '+':
        data[data_ptr] += 1
    elif inst == '-':
        data[data_ptr] -= 1
    elif inst == '.':
        print(chr(data[data_ptr]), end="")
    elif inst == ',':
        data[data_ptr] = int(raw_input("-->"))
    elif inst == '[':
        if data[data_ptr] == 0:
            while program[inst_ptr] != ']':
                inst_ptr += 1
    elif inst == ']':
        if data[data_ptr] != 0:
            while program[inst_ptr] != '[':
                inst_ptr -= 1

    inst_ptr += 1