Parser for irc messages

parser.py

"""
Parses incoming IRC messages, and formats outgoing IRC messages.
"""

def parse_message (string):
	"""	Parse an IRC message in the form:
		[:{source} ]{command}[ parameters][ :{trailing}]
	"""
	# Default variables for parameters and trailing,
	# as it is possible neither will be assigned
	parameters, trailing = [], None
	
	# Remove the source from the string if it has one
	source, string = string[1:].split(' ',1) if string[0] == ':' else None, string
	
	# Get the command from the string
	command, string = get_token(string)
	
	# While there are still elements in the string to parse,
	# get either the trailing element or another parameter
	while string:
		if string[0] == ':':
			trailing = string[1:].strip()
			break
		else:
			param, string = get_token(string)
			parameters.append(param)
	
	# Return the message as a tuple of 4 elements
	return source, command, parameters, trailing

def get_token (string):
	split = string.split(' ',1)
	return (split[0], None) if len(split) == 1 else tuple(split)

def format_message (command, parameters = None, trailing = None):
	# Is this actually needed?
	if not parameters and not trailing:
		raise Exception("Either parameters or trailing must be used!")
	
	string = "{} ".format(command)
	
	# Join the parameters into a space seperated string,
	# then append them to the string
	if parameters: string = "{} {}".format(string, ' '.join(parameters))
		
	# Append the trailing parameter
	if trailing: string = "{} :{}".format(string, trailing)
		
	return string