Hacky interpreter for a subset of brainfuck

hacky-interp.py

#######################################################
# A hacky interpreter for the ><+-[] language
# 2018 (c) Jay Bosamiya
#######################################################

#######################################################
# Update "program" and "cells" to whatever you chose
#######################################################

program = "INPUT PROGRAM HERE" # For example, try "+>+"
cells = [0, 0, 0, 0, 0, 0]  # Starting values for the cells

#######################################################
# DO NOT MODIFY ANYTHING BELOW THIS LINE
#######################################################

pc = 0
dp = 0


def move_right():
    global pc, dp, cells
    dp += 1
    while len(cells) <= dp:
        cells += [0]
    pc += 1


def move_left():
    global pc, dp
    assert dp > 0, "Moving left past the left end"
    dp -= 1
    pc += 1


def increment():
    global pc, cells
    cells[dp] += 1
    cells[dp] %= 255
    pc += 1


def decrement():
    global pc, cells
    if cells[dp] == 0:
        cells[dp] = 256
    cells[dp] -= 1
    pc += 1


def open_brace():
    global pc
    pc += 1
    if cells[dp] != 0:
        return
    else:
        c = 1
        while c > 0:
            if program[pc] == '[':
                c += 1
            elif program[pc] == ']':
                c -= 1
            pc += 1


def close_brace():
    global pc
    if cells[dp] == 0:
        pc += 1
        return
    else:
        pc -= 1
        c = 1
        while c > 0:
            if program[pc] == '[':
                c -= 1
            elif program[pc] == ']':
                c += 1
            pc -= 1
        pc += 1


while pc < len(program):
    if program[pc] in '><+-[]':
        # print program, pc, dp
        # print (' ' * pc) + '^'
        {
            '>': move_right,
            '<': move_left,
            '+': increment,
            '-': decrement,
            '[': open_brace,
            ']': close_brace
        }[program[pc]]()
    else:
        pc += 1


while len(cells) > 0 and cells[-1] == 0:
    cells = cells[:-1]

cells += [0, 0, 0]

print "Result:", ' '.join(str(x) + ',' for x in cells), '...'