aenumerate - enumerate for async for

Python's new async/await syntax helps a lot with writing async code. Here's a little utility that provides the async equivalent of enumerate.

	"""aenumerate - enumerate for async for"""
	import asyncio
	from collections import abc
	class aenumerate(abc.AsyncIterator):
	"""enumerate for async for"""
	def __init__(self, aiterable, start=0):
	self._aiterable = aiterable
	self._i = start - 1
	async def __aiter__(self):
	self._ait = await self._aiterable.__aiter__()
	return self
	async def __anext__(self):
	# self._ait will raise the apropriate AsyncStopIteration
	val = await self._ait.__anext__()
	self._i += 1
	return self._i, val
	# Example usage
	async def iter_lines(host, port):
	"""Iterator over lines from host:port, print them with line number"""
	rdr, wtr = await asyncio.open_connection(host, port)
	async for lnum, line in aenumerate(rdr, 1):
	line = line.decode().rstrip()
	print('[{}:{}] {:02d} {}'.format(host, port, lnum, line))
	if __name__ == '__main__':
	from argparse import ArgumentParser
	parser = ArgumentParser(description='enumerate lines from TCP server')
	parser.add_argument('host', help='host to connect to')
	parser.add_argument('port', help='port to connect to', type=int)
	args = parser.parse_args()
	loop = asyncio.get_event_loop()
	loop.run_until_complete(iter_lines(args.host, args.port))
	loop.close()
	# Run server: nc -lc -p 7654 < some-file
	# (or on osx: nc -l 7654 < some-file)

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