functional parenthesis balancer

gistfile1.py

def balance(chars):
	def testchar(chars, open, closed)
        	if (open < closed):
            		return False	
        	if not chars: #chars is empty
            		return (open == closed)
		 if (chars.head == '('):
			testchar(chars.tail, open+1, closed)
		elif (chars.head == ')'):
			testchar(chars.tail, open, closed+1)
		else:
			testchar(chars.tail,open,closed)
		
	testchar(chars,0,0)