"""TupleStructType: a metaclass to create classes based on tuple
with named access to the tuple members"""
__version__= (1, 0, 0)
import sys
if sys.hexversion<0x02030000:
	from tzot.future import enumerate # simulate 2.3 enumerate

class TupleStructType(type):
	"""Create a tuple derived class with named members"""

	def __new__(cls, members):
		"""Create a new class with the members specified as words in a string"""
		member_list= members.split()
		attributes= {}

		def new_cls_new(new_cls, *data):
			return tuple.__new__(new_cls, data)
		attributes['__new__']= new_cls_new
		attributes['__slots__']= () # important, so the new class won't have a dict

		# factory for the property get functions
		def property_factory(index):
			def property_get(self):
				try:
					value= self[index]
				except IndexError:
					value= None
				return value
			return property_get

		# getstate, setstate for pickling
		def my_getstate(self):
			return tuple(self)
		attributes['__getstate__']= my_getstate
		def my_setstate(self, data):
			self= self.__class__(*data)
		attributes['__setstate__']= my_setstate

		# create the property get functions
		for index, member in enumerate(member_list):
			attributes[member]= property(property_factory(index))
		attributes['__doc__']="TupleStruct(%s)" % ','.join(member_list)

		cls_name= "TplStr_" + '_'.join(member_list)
		new_cls= type.__new__(cls, cls_name, (tuple,), attributes)
		globals()[cls_name]= new_cls # add the name to the module for pickle use
		return new_cls

if __name__=="__main__":
	Person= TupleStructType("name city age") # Person is a class now
	person= Person("Chris", "Athens", 30)
	tpl= ("Chris", "Athens", 30)
	person2= Person(*tpl)
	if person[0]!=person.name or person[1]!=person.city or person[2]!=person.age:
		print "named access failed"
	if person!=tpl:
		print "comparison to tuple failed"
	if person!=person2:
		print "comparison to other person failed"
	person0= Person("Lena")
	if person0.age is not None:
		print "missing members are not None"
	print person0.__class__
	print dir(person0)