Refactored some code to try and make it more inline with best pratices. Renamed parser as it conflicted with a standard Python library.

base_unit.py

@@ -0,0 +1,71 @@
+class Token:
+	# Represents the single smallest unit that makes up an expression.
+	
+	def __init__(self, value, type, is_negative_variable = False):
+		self.value = value
+		self.type = type
+		self.is_negative_variable = is_negative_variable
+		
+	def __str__(self):
+		return "Value: %s" %(self.value)
+
+class TokenType:
+	add = 0
+	subtract = 1
+	multiply = 2
+	divide = 3
+	power = 4
+	variable = 5
+	constant = 6
+	exp_start = 7
+	exp_end = 8
+	unknown = 9
+
+	OPERATOR_VERBS = {
+		0 : "Adding",
+		1 : "Subtracting",
+		2 : "Multiplying",
+		3 : "Dividing",
+		4 : "Raising"
+	}
+	
+	TOKEN_NAMES = {
+		0 : "Addition",
+		1 : "Subtraction",
+		2 : "Multiplication",
+		3 : "Division",
+		4 : "Power",
+		5 : "Variable",
+		6 : "Constant",
+		7 : "Expression Start",
+		8 : "Expression End",
+		9 : "Unknown"
+	}
+
+	OPERATORS = {
+		'+' : add,
+		'-' : subtract,
+		'*' : multiply,
+		'^' : power,
+		'/' : divide
+	}
+
+	@staticmethod
+	def get_operator_verb(token):
+		# Returns the verb that corresponds to the supplied Token object's value field, or
+		# throws an error if the Token object isn't a mathmatical operator.
+		if not token in TokenType.OPERATOR_VERBS:
+			raise ValueError("An operator verb could not be found.", "token")
+		return TokenType.OPERATOR_VERBS[token]
+
+	@staticmethod
+	def get_operator(character):
+        # Accepts an individual character and returns either the mathmatical operator TokenType or unknown.
+		if not character in TokenType.OPERATORS:
+			return TokenType.unknown
+		return TokenType.OPERATORS[character]
+	
+	@staticmethod
+	def get_token_type_name(tokenType):
+		# Returns the token's full name based on the TokenType value.
+		return TokenType.TOKEN_NAMES[tokenType]