parser_without_lexer.py

# coding: utf-8

class Parser:
	def __init__(self):
		self.string = ""
		self.token = None

	def get_token(self):

		if(len(self.string)):
			self.token = self.string[0]
			self.string = self.string[1:]
		else:
			self.token = ""


	def expect(self,value):
		if self.token != value:
			raise Exception("Syntax Error")

		self.get_token()

	def curly(self):
		self.expect("{")
		self.stmt(1)
		self.expect("}")

	def bracket(self):
		self.expect("(")
		self.stmt(1)
		self.expect(")")		

	def square(self):
		self.expect("[")
		self.stmt(1)
		self.expect("]")

	def stmt(self,p):
		if self.token == "":
			return

		if self.token == "{":
			self.curly()
			self.stmt(p)
		elif self.token == "(":
			self.bracket()
			self.stmt(p)
		elif self.token == "[":
			self.square()
			self.stmt(p)
		else:
			if p == 1:
				return
			else:
				raise Exception("Syntax error")

		return

	def __call__(self,string):
		return self.work(string)

	def work(self,string):
		self.string = string

		while True:
			try:
				self.get_token()
				if(self.token == ""):
					break
				self.stmt(0)

			except Exception as e:
				return False

		return True

test_without_lexer.py

# coding: utf-8

import unittest
from program import Parser

class ProgramTest(unittest.TestCase):
	def setUp(self):
		self.parser = Parser()

		self.case_1 = "[({()}([])[(){}])]"
		self.case_2 = "((())())"
		self.case_3 = "{}}"
		self.case_4 = "(}"
		self.case_5 = "(())("
		self.case_6 = "(()[])([])"

	def test_parser(self):
		self.assertTrue(self.parser(self.case_1))
		self.assertTrue(self.parser(self.case_2))
		self.assertFalse(self.parser(self.case_3))
		self.assertFalse(self.parser(self.case_4))
		self.assertFalse(self.parser(self.case_5))
		self.assertTrue(self.parser(self.case_6))

if __name__ == "__main__":
	unittest.main()