Formal grammar interpreter

exec.py

#Execute a type 3 grammar

rules2 = """
S -> ATC
A -> aA | 
C -> cC | 
T -> abT | ab
"""

class bcolors:
    HEADER = '\033[95m'
    OKBLUE = '\033[94m'
    OKGREEN = '\033[92m'
    WARNING = '\033[93m'
    FAIL = '\033[91m'
    ENDC = '\033[0m'
    BOLD = '\033[1m'
    UNDERLINE = '\033[4m'

def print_colored(text, color):
	print(color, text, bcolors.ENDC) 

def parse_rules(text):
	rules = {}
	for line in text.split('\n'):
		if line.strip():
			symb, choices = line.split('->')
			rules[symb.strip()] = \
				[x.strip() for x in choices.strip().split('|')]
	return rules

def apply_rules(s, rules, limit=5):
	terminal = True
	for x in s:
		if x in rules:
			terminal = False
			break
	if terminal:
		print_colored(s, bcolors.OKGREEN)
	else:
		print_colored(s, bcolors.OKBLUE)
	if limit == 0:
		return
	for i,x in enumerate(s):
		if x in rules:
			for y in rules[x]:
				t = list(s)
				t[i] = y
				new_s = ''.join(t)
				apply_rules(new_s, rules, limit=limit-1)

rules = parse_rules(rules2)
print(rules)
apply_rules	('S', rules)