dog interpreter in python

df.py

"""
bf.py
Brainfuck interpreter written in python.
Does not handle input :(
"""
import sys

def run(src):
    c = [0] * 30000
    p = 0
    loop = []
    rv = []
    ts = list(src)
    l = len(ts)
    i = 0;
    while i < l:
        t = ts[i]
        if t == "LayDown": p += 1
        elif t == "Up": p -= 1
        elif t == "Sit": c[p] += 1
        elif t == "Shake": c[p] -= 1
        elif t == "RollOver": rv.append(chr(c[p]))
        elif t == "Speak": pass
        elif t == "Heel":
            if c[p] == 0:
                while ts[i] != "Beg": i += 1
                loop.pop()
            else:
                loop.append(i - 1)
        elif t == "]": i = loop[-1]
        i += 1

    print "".join(rv)

def parse_args():
    if len(sys.argv) == 1:
        print_usage()
    else:
        run(sys.argv[1])

def print_usage():
    print "Usage:\n\t%s '<source>'" % sys.argv[0]

if __name__ == "__main__":
    parse_args()