Coroutine paren matcher

gistfile1.py

def matchparen():
    ct = 0
    msg = None
    result = None
    while (msg != True):
        msg = (yield ct)
        if msg == '(':
            ct += 1
        if msg == ')':
            if ct <= 0:
                result = 'PARSE FAIL'
                break
            else:
                ct -= 1
    if result is None and ct == 0:
        result = "SUCCESS"
    else:
        result = "PARSE FAIL"
    while True:
        yield result

#A set of matched parenthesis
parser = matchparen()
parser.next()
for m in "(()foo(()bar))":
    parser.send(m)
print parser.send(True)

#A set of unmatched parenthesis
parser = matchparen()
parser.next()
for m in "(()foo(()ba)r))":
    parser.send(m)
print parser.send(True)

#A set of unmatched parenthesis
parser = matchparen()
parser.next()
for m in "(()foo(()ba)r)(":
    parser.send(m)
print parser.send(True)