[Python-ideas] reiter: decorator to make generators reiterable

[Mathias Panzenböck]

I think this decorator sould be included in itertools:

from functools import wraps

class ReIter(object):
	__slots__ = 'f', 'args', 'kwargs'

	def __init__(self,f,args,kwargs):
		self.f      = f
		self.args   = args
		self.kwargs = kwargs
	
	def __iter__(self):
		return self.f(*self.args, **self.kwargs)

def reiter(f):
	@wraps(f)
	def _reiter(*args,**kwargs):
		return ReIter(f,args,kwargs)
	return _reiter


Using this you can iterate over the return value of a generator decorated with reiter as often as 
you like (and not just once):

@reiter
def gen(x,y):
	for i in xrange(x):
		yield i*y

g = gen(5,3)
for x in g:
	sys.stdout.write('%r\n' % x)
sys.stdout.write('\n')
for x in g:
	sys.stdout.write('%r\n' % x)


The difference to tee is that old values are not remembered but the generator is evaluated when 
__iter__() is called. This might come in handy when you implement methods like items(), values() and 
keys() in a custom dict implementation.

Or is there already such a thing and I missed it?

	-panzi


PS: Maybe it should be called regen/ReGen instead of reiter/ReIter?
PPS: Funny thing, both "Reiter" and "Regen" are german words. Reiter = rider or tab; Regen = rain.