Use grequests.imap in poll script

poll.py

@@ -8,26 +8,26 @@ import json
 from argparse import ArgumentParser
 
 # exchanges as (url, id, response_indices_last, currency)
-exchanges = [
-    ('https://btc-e.com/api/3/ticker/btc_usd',
-        'btce', ('btc_usd', 'last'), 'USD'),
-    ('https://api.gdax.com/products/BTC-USD/ticker',
-        'coinbase', ('price',), 'USD'),
-    ('https://www.bitstamp.net/api/v2/ticker/btcusd/',
-        'bitstamp', ('last',), 'USD'),
-    ('https://api.bitfinex.com/v1/pubticker/btcusd',
-        'bitfinex', ('last_price',), 'USD'),
-    ('https://data.btcchina.com/data/ticker?market=btccny',
-        'btcchina', ('ticker', 'last'), 'CNY'),
-    ('http://api.huobi.com/staticmarket/ticker_btc_json.js',
-        'huobi', ('ticker', 'last'), 'CNY'),
-    ('https://www.okcoin.com/api/v1/ticker.do?symbol=btc_usd',
-        'okcoin', ('ticker', 'last'), 'CNY'),
-    ('https://api.kraken.com/0/public/Ticker?pair=XXBTZEUR',
-        'kraken', ('result', 'XXBTZEUR', 'c', 0), 'EUR'),
-    ('https://api.coinmarketcap.com/v1/ticker/bitcoin/',
-        'coinmarketcap', (0, 'market_cap_usd'), 'USD'),
-]
+exchanges = {
+    'https://btc-e.com/api/3/ticker/btc_usd':
+        ('btce', ('btc_usd', 'last'), 'USD'),
+    'https://api.gdax.com/products/BTC-USD/ticker':
+        ('coinbase', ('price',), 'USD'),
+    'https://www.bitstamp.net/api/v2/ticker/btcusd/':
+        ('bitstamp', ('last',), 'USD'),
+    'https://api.bitfinex.com/v1/pubticker/btcusd':
+        ('bitfinex', ('last_price',), 'USD'),
+    'https://data.btcchina.com/data/ticker?market=btccny':
+        ('btcchina', ('ticker', 'last'), 'CNY'),
+    'http://api.huobi.com/staticmarket/ticker_btc_json.js':
+        ('huobi', ('ticker', 'last'), 'CNY'),
+    'https://www.okcoin.com/api/v1/ticker.do?symbol=btc_usd':
+        ('okcoin', ('ticker', 'last'), 'CNY'),
+    'https://api.kraken.com/0/public/Ticker?pair=XXBTZEUR':
+        ('kraken', ('result', 'XXBTZEUR', 'c', 0), 'EUR'),
+    'https://api.coinmarketcap.com/v1/ticker/bitcoin/':
+        ('coinmarketcap', (0, 'market_cap_usd'), 'USD'),
+}
 
 
 def handle_error(req, e):
@@ -52,7 +52,7 @@ if __name__ == '__main__':
     root = args.dir
 
     if args.list:
-        for url, exid, indices, currency in exchanges:
+        for url, (exid, indices, currency) in exchanges.iteritems():
             print exid
             print '  url:     ', url
             print '  currency:', currency
@@ -63,7 +63,7 @@ if __name__ == '__main__':
 
     # clean up created files on exit
     def remove_files():
-        for url, exid, indices, currency in exchanges:
+        for url, (exid, indices, currency) in exchanges.iteritems():
             path = root + '/' + exid
             if os.path.exists(path):
                 os.remove(path)
@@ -91,20 +91,27 @@ if __name__ == '__main__':
             if diff < args.interval:
                 time.sleep(args.interval - diff)
 
-            requests = (grequests.get(ex[0], timeout=args.timeout)
-                        for ex in exchanges)
-            responses = grequests.map(requests, exception_handler=handle_error)
+            requests = (grequests.get(url, timeout=args.timeout)
+                        for url in exchanges.iterkeys())
 
-            for (url, exid, indices, currency), res in zip(exchanges, responses):
+            for res in grequests.imap(requests, exception_handler=handle_error):
                 if res is None:
-                    print >>sys.stderr, 'Unknown error at %s' % exid
-                elif res.status_code != 200:
+                    continue
+
+                exid, indices, currency = exchanges[res.request.url]
+
+                try:
+                    res_json = res.json()
+
+                    if res.status_code != 200:
+                        if 'error' in res_json:
+                            print >>sys.stderr, 'Server error %d at %s: %s' % \
+                                    (res.status_code, exid, res_json['error'])
+                        else:
                             print >>sys.stderr, 'Server error %d at %s' % \
                                     (res.status_code, exid)
                     else:
-                    try:
-                        last = res.json()
-
+                        last = res_json
                         for i in indices:
                             last = last[i]
 
@@ -115,6 +122,7 @@ if __name__ == '__main__':
                         }
 
                         with open(root + '/' + exid, 'w') as f:
+                            print >>sys.stderr, 'Updating', exid
                             json.dump(status, f)
 
                 except ValueError as e: