Python Boolean Expression Parser/Evaluator

boolparser.py

"""
Grammar:
========
Expression --> AndTerm { OR AndTerm}+
AndTerm --> Condition { AND Condition}+
Condition --> Terminal (>,<,>=,<=,==) Terminal | (Expression)
Terminal --> Number or String or Variable

Usage:
======
from boolparser import *
p = BooleanParser('<expression text>')
p.evaluate(variable_dict) # variable_dict is a dictionary providing values for variables that appear in <expression text>
"""

class TokenType:
	NUM, STR, VAR, GT, GTE, LT, LTE, EQ, NEQ, LP, RP, AND, OR = range(13)

class TreeNode:
	tokenType = None
	value = None
	left = None
	right = None

	def __init__(self, tokenType):
		self.tokenType = tokenType

class Tokenizer:
	expression = None
	tokens = None
	tokenTypes = None
	i = 0

	def __init__(self, exp):
		self.expression = exp

	def next(self):
		self.i += 1
		return self.tokens[self.i-1]
	
	def peek(self):
		return self.tokens[self.i]
	
	def hasNext(self):
		return self.i < len(self.tokens)

	def nextTokenType(self):
		return self.tokenTypes[self.i]
	
	def nextTokenTypeIsOperator(self):
		t = self.tokenTypes[self.i]
		return t == TokenType.GT or t == TokenType.GTE \
			or t == TokenType.LT or t == TokenType.LTE \
			or t == TokenType.EQ or t == TokenType.NEQ

	def tokenize(self):
		import re
		reg = re.compile(r'(\bAND\b|\bOR\b|!=|==|<=|>=|<|>|\(|\))')
		self.tokens = reg.split(self.expression)
		self.tokens = [t.strip() for t in self.tokens if t.strip() != '']

		self.tokenTypes = []
		for t in self.tokens:
			if t == 'AND':
				self.tokenTypes.append(TokenType.AND)
			elif t == 'OR':
				self.tokenTypes.append(TokenType.OR)
			elif t == '(':
				self.tokenTypes.append(TokenType.LP)
			elif t == ')':
				self.tokenTypes.append(TokenType.RP)
			elif t == '<':
				self.tokenTypes.append(TokenType.LT)
			elif t == '<=':
				self.tokenTypes.append(TokenType.LTE)
			elif t == '>':
				self.tokenTypes.append(TokenType.GT)
			elif t == '>=':
				self.tokenTypes.append(TokenType.GTE)
			elif t == '==':
				self.tokenTypes.append(TokenType.EQ)
			elif t == '!=':
				self.tokenTypes.append(TokenType.NEQ)
			else:
				# number of string or variable
				if t[0] == '"' and t[-1] == '"':
					self.tokenTypes.append(TokenType.STR)
				else:
					try:
						number = float(t)
						self.tokenTypes.append(TokenType.NUM)
					except:
						if re.search('^[a-zA-Z_]+$', t):
							self.tokenTypes.append(TokenType.VAR)
						else:
							self.tokenTypes.append(None)

class BooleanParser:
	tokenizer = None
	root = None

	def __init__(self, exp):
		self.tokenizer = Tokenizer(exp)
		self.tokenizer.tokenize()
		self.parse()

	def parse(self):
		self.root = self.parseExpression()

	def parseExpression(self):
		andTerm1 = self.parseAndTerm()
		while self.tokenizer.hasNext() and self.tokenizer.nextTokenType() == TokenType.OR:
			self.tokenizer.next()
			andTermX = self.parseAndTerm()
			andTerm = TreeNode(TokenType.OR)
			andTerm.left = andTerm1
			andTerm.right = andTermX
			andTerm1 = andTerm
		return andTerm1

	def parseAndTerm(self):
		condition1 = self.parseCondition()
		while self.tokenizer.hasNext() and self.tokenizer.nextTokenType() == TokenType.AND:
			self.tokenizer.next()
			conditionX = self.parseCondition()
			condition = TreeNode(TokenType.AND)
			condition.left = condition1
			condition.right = conditionX
			condition1 = condition
		return condition1

	def parseCondition(self):
		if self.tokenizer.hasNext() and self.tokenizer.nextTokenType() == TokenType.LP:
			self.tokenizer.next()
			expression = self.parseExpression()
			if self.tokenizer.hasNext() and self.tokenizer.nextTokenType() == TokenType.RP:
				self.tokenizer.next()
				return expression
			else:
				raise Exception("Closing ) expected, but got " + self.tokenizer.next())

		terminal1 = self.parseTerminal()
		if self.tokenizer.hasNext() and self.tokenizer.nextTokenTypeIsOperator():
			condition = TreeNode(self.tokenizer.nextTokenType())
			self.tokenizer.next()
			terminal2 = self.parseTerminal()
			condition.left = terminal1
			condition.right = terminal2
			return condition
		else:
			raise Exception('Operator expected, but got ' + self.tokenizer.next())
	
	def parseTerminal(self):
		if self.tokenizer.hasNext():
			tokenType = self.tokenizer.nextTokenType()
			if tokenType == TokenType.NUM:
				n = TreeNode(tokenType)
				n.value = float(self.tokenizer.next())
				return n
			elif tokenType == TokenType.STR or tokenType == TokenType.VAR:
				n = TreeNode(tokenType)
				n.value = self.tokenizer.next()
				return n
			else:
				raise Exception('NUM, STR, or VAR expected, but got ' + self.tokenizer.next())
		
		else:
			raise Exception('NUM, STR, or VAR expected, but got ' + self.tokenizer.next())
	
	def evaluate(self, variable_dict):
		return self.evaluateRecursive(self.root, variable_dict)
	
	def evaluateRecursive(self, treeNode, variable_dict):
		if treeNode.tokenType == TokenType.NUM or treeNode.tokenType == TokenType.STR:
			return treeNode.value
		if treeNode.tokenType == TokenType.VAR:
			return variable_dict.get(treeNode.value)
		
		left = self.evaluateRecursive(treeNode.left, variable_dict)
		right = self.evaluateRecursive(treeNode.right, variable_dict)
		if treeNode.tokenType == TokenType.GT:
			return left > right
		elif treeNode.tokenType == TokenType.GTE:
			return left >= right
		elif treeNode.tokenType == TokenType.LT:
			return left < right
		elif treeNode.tokenType == TokenType.LTE:
			return left <= right
		elif treeNode.tokenType == TokenType.EQ:
			return left == right
		elif treeNode.tokenType == TokenType.NEQ:
			return left != right
		elif treeNode.tokenType == TokenType.AND:
			return left and right
		elif treeNode.tokenType == TokenType.OR:
			return left or right
		else:
			raise Exception('Unexpected type ' + str(treeNode.tokenType))

		

please provide same code for c# or java

First of all, it is very simple and intuitive to use! Kudos!
Also, I have included support for str.startswith and simplified string matching in my forked gist. Can you review and include it in this gist??

I've forked and added support for a LIKE operator, a BOOLEAN type, and a function to translate to DNF: https://gist.github.com/joocer/9e939b2bda90d56bf48b8ff78eeba0e7