Ported Lahiru's tokneizer code over. Appears to work fine. Also did some house keeping.

tokenizer.py

@@ -0,0 +1,88 @@
+import token
+
+def get_tokens_from_expression_string(expression_string):
+	"""
+	Takes user input of an actuarial formula and parses the formula to id its components.
+	:return: tokens (List of objects of CToken class).
+	"""
+	tokens = []  # List of objects of CToken class
+	tmp = ""
+	parsing_number = False
+	symbols_dic = {}  # Dictionary to keep track of the no. of times each variable appears.
+
+	for i in range(0, len(expression_string)):
+		c = expression_string[i]
+		if c == '.' or c.isdigit():
+			if tmp.count('.') == 1:
+				raise ValueError("Invalid grammar, to many periods in number!")
+			if len(tokens) > 1:
+				lookBehind = tokens[-1]
+				if lookBehind.type == token.TokenType.exp_end:
+					tokens.append(token.CToken("^", token.TokenType.power))
+			if (i + 1) == len(expression_string):
+				tokens.append(token.CToken(tmp + c, token.TokenType.constant))
+			parsing_number = True
+			tmp = tmp + c
+			continue
+		elif c == '(':
+			if parsing_number:
+				tokens.append(token.CToken(tmp, token.TokenType.constant))
+				tokens.append(token.CToken("*", token.TokenType.multiply))
+			tokens.append(token.CToken("(", token.TokenType.exp_start))
+			parsing_number = False
+			tmp = ""
+			continue
+		elif c == ')':
+			if parsing_number:				
+				tokens.append(token.CToken(tmp, token.TokenType.constant))
+			tokens.append(token.CToken(")", token.TokenType.exp_end))
+			parsing_number = False
+			tmp = ""
+			continue
+		elif token.TokenType.get_operator(c) != token.TokenType.unknown:
+			if parsing_number:
+				tokens.append(token.CToken(tmp, token.TokenType.constant))
+			tokens.append(token.CToken(c, token.TokenType.get_operator(c)))
+			parsing_number = False
+			tmp = ""
+			continue
+		elif c != ' ':
+			if len(tokens) > 1:
+				lookBehind = tokens[-1]
+				if lookBehind.type == TokenType.exp_end:
+					tokens.append(token.CToken("^", token.TokenType.power))
+			if (i + 1) < len(expression_string):
+				lookAHead = expression_string[i + 1]
+				if lookAHead == '(':
+					tokens.append(token.CToken(c, token.TokenType.variable))
+					tokens.append(token.CToken("*", token.TokenType.multiply))
+					tmp = ""
+					parsing_number = False
+					continue
+			if parsing_number:
+				tokens.append(token.CToken(tmp, token.TokenType.constant))
+				tokens.append(token.CToken("*", token.TokenType.multiply))
+			if c in symbols_dic.keys():
+				symbols_dic[c] += 1
+			else:
+				symbols_dic[c] = 1
+			tokens.append(token.CToken(c + str(symbols_dic[c]), token.TokenType.variable))
+			parsing_number = False
+			tmp = ""
+
+	return tokens
+
+def operate(n1, n2, tokenType):
+	if tokenType == token.TokenType.add:
+		print("Adding %d and %d to get %d." %(n1, n2, n1 + n2))
+	elif tokenType == token.TokenType.subtract:
+		print("Subtracting %d and %d to get %d." %(n1, n2, n1 - n2))
+	elif tokenType == token.TokenType.multiply:
+		print("Multiplying %d and %d to get %d" %(n1, n2, n1 * n2))
+	elif tokenType == token.TokenType.divide:
+		print("Dividing %d and %d to get %d" %(n1, n2, n1 / n2))
+	elif tokenType == token.TokenType.power:
+		print("Raising %d to the power of %d to get %d" %(n1, n2, n1**n2))
+	else:
+		raise ValueError("Invalid operator value.")
+