It would come as no surprise to anyone that I am interested in bitcoins and virtual currencies. I've been keeping an eye on virtual currencies for many years, and it is part of the reason a few months ago, I started writing a python library for collecting currency exchange rates and trade on virtual currency exchanges. I decided to name the end result valutakrambod, which perhaps can be translated to small currency shop.
The library uses the tornado python library to handle HTTP and websocket connections, and provide a asynchronous system for connecting to and tracking several services. The code is available from github.
There are two example clients of the library. One is very simple and list every updated buy/sell price received from the various services. This code is started by running bin/btc-rates and call the client code in valutakrambod/client.py. The simple client look like this:
import functools
import tornado.ioloop
import valutakrambod
class SimpleClient(object):
def __init__(self):
self.services = []
self.streams = []
pass
def newdata(self, service, pair, changed):
print("%-15s %s-%s: %8.3f %8.3f" % (
service.servicename(),
pair[0],
pair[1],
service.rates[pair]['ask'],
service.rates[pair]['bid'])
)
async def refresh(self, service):
await service.fetchRates(service.wantedpairs)
def run(self):
self.ioloop = tornado.ioloop.IOLoop.current()
self.services = valutakrambod.service.knownServices()
for e in self.services:
service = e()
service.subscribe(self.newdata)
stream = service.websocket()
if stream:
self.streams.append(stream)
else:
# Fetch information from non-streaming services immediately
self.ioloop.call_later(len(self.services),
functools.partial(self.refresh, service))
# as well as regularly
service.periodicUpdate(60)
for stream in self.streams:
stream.connect()
try:
self.ioloop.start()
except KeyboardInterrupt:
print("Interrupted by keyboard, closing all connections.")
pass
for stream in self.streams:
stream.close()
The library client loops over all known "public" services, initialises it, subscribes to any updates from the service, checks and activates websocket streaming if the service provide it, and if no streaming is supported, fetches information from the service and sets up a periodic update every 60 seconds. The output from this client can look like this:
Bl3p BTC-EUR: 5687.110 5653.690 Bl3p BTC-EUR: 5687.110 5653.690 Bl3p BTC-EUR: 5687.110 5653.690 Hitbtc BTC-USD: 6594.560 6593.690 Hitbtc BTC-USD: 6594.560 6593.690 Bl3p BTC-EUR: 5687.110 5653.690 Hitbtc BTC-USD: 6594.570 6593.690 Bitstamp EUR-USD: 1.159 1.154 Hitbtc BTC-USD: 6594.570 6593.690 Hitbtc BTC-USD: 6594.580 6593.690 Hitbtc BTC-USD: 6594.580 6593.690 Hitbtc BTC-USD: 6594.580 6593.690 Bl3p BTC-EUR: 5687.110 5653.690 Paymium BTC-EUR: 5680.000 5620.240
The exchange order book is tracked in addition to the best buy/sell price, for those that need to know the details.
The other example client is focusing on providing a curses view with updated buy/sell prices as soon as they are received from the services. This code is located in bin/btc-rates-curses and activated by using the '-c' argument. Without the argument the "curses" output is printed without using curses, which is useful for debugging. The curses view look like this:
Name Pair Bid Ask Spr Ftcd Age
BitcoinsNorway BTCEUR 5591.8400 5711.0800 2.1% 16 nan 60
Bitfinex BTCEUR 5671.0000 5671.2000 0.0% 16 22 59
Bitmynt BTCEUR 5580.8000 5807.5200 3.9% 16 41 60
Bitpay BTCEUR 5663.2700 nan nan% 15 nan 60
Bitstamp BTCEUR 5664.8400 5676.5300 0.2% 0 1 1
Bl3p BTCEUR 5653.6900 5684.9400 0.5% 0 nan 19
Coinbase BTCEUR 5600.8200 5714.9000 2.0% 15 nan nan
Kraken BTCEUR 5670.1000 5670.2000 0.0% 14 17 60
Paymium BTCEUR 5620.0600 5680.0000 1.1% 1 7515 nan
BitcoinsNorway BTCNOK 52898.9700 54034.6100 2.1% 16 nan 60
Bitmynt BTCNOK 52960.3200 54031.1900 2.0% 16 41 60
Bitpay BTCNOK 53477.7833 nan nan% 16 nan 60
Coinbase BTCNOK 52990.3500 54063.0600 2.0% 15 nan nan
MiraiEx BTCNOK 52856.5300 54100.6000 2.3% 16 nan nan
BitcoinsNorway BTCUSD 6495.5300 6631.5400 2.1% 16 nan 60
Bitfinex BTCUSD 6590.6000 6590.7000 0.0% 16 23 57
Bitpay BTCUSD 6564.1300 nan nan% 15 nan 60
Bitstamp BTCUSD 6561.1400 6565.6200 0.1% 0 2 1
Coinbase BTCUSD 6504.0600 6635.9700 2.0% 14 nan 117
Gemini BTCUSD 6567.1300 6573.0700 0.1% 16 89 nan
Hitbtc+BTCUSD 6592.6200 6594.2100 0.0% 0 0 0
Kraken BTCUSD 6565.2000 6570.9000 0.1% 15 17 58
Exchangerates EURNOK 9.4665 9.4665 0.0% 16 107789 nan
Norgesbank EURNOK 9.4665 9.4665 0.0% 16 107789 nan
Bitstamp EURUSD 1.1537 1.1593 0.5% 4 5 1
Exchangerates EURUSD 1.1576 1.1576 0.0% 16 107789 nan
BitcoinsNorway LTCEUR 1.0000 49.0000 98.0% 16 nan nan
BitcoinsNorway LTCNOK 492.4800 503.7500 2.2% 16 nan 60
BitcoinsNorway LTCUSD 1.0221 49.0000 97.9% 15 nan nan
Norgesbank USDNOK 8.1777 8.1777 0.0% 16 107789 nan
The code for this client is too complex for a simple blog post, so you will have to check out the git repository to figure out how it work. What I can tell is how the three last numbers on each line should be interpreted. The first is how many seconds ago information was received from the service. The second is how long ago, according to the service, the provided information was updated. The last is an estimate on how often the buy/sell values change.
If you find this library useful, or would like to improve it, I would love to hear from you. Note that for some of the services I've implemented a trading API. It might be the topic of a future blog post.
As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.