added examples/py/async-bittrex-orderbook.py ccxt#345

examples/py/async-bittrex-orderbook.py

@@ -0,0 +1,26 @@
+# -*- coding: utf-8 -*-
+
+import asyncio
+import os
+import sys
+
+root = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+sys.path.append(root)
+
+import ccxt.async as ccxt  # noqa: E402
+
+exchange = ccxt.bittrex()
+
+
+async def poll():
+    while True:
+        yield await exchange.fetch_order_book('BTC/USDT')
+        await asyncio.sleep(exchange.rateLimit / 1000)
+
+
+async def main():
+    async for orderbook in poll():
+        print(orderbook['bids'][0], orderbook['asks'][0])
+
+
+asyncio.get_event_loop().run_until_complete(main())