blog/data/2018-09-29-bitcoin-valutakrambod.txt

   1 Title: Valutakrambod - A python and bitcoin love story
   2 Tags: english, bitcoin
   3 Date: 2018-09-29 22:20
   4
   5 <p>It would come as no surprise to anyone that I am interested in
   6 bitcoins and virtual currencies.  I've been keeping an eye on virtual
   7 currencies for many years, and it is part of the reason a few months
   8 ago, I started writing a python library for collecting currency
   9 exchange rates and trade on virtual currency exchanges.  I decided to
  10 name the end result valutakrambod, which perhaps can be translated to
  11 small currency shop.</p>
  12
  13 <p>The library uses the tornado python library to handle HTTP and
  14 websocket connections, and provide a asynchronous system for
  15 connecting to and tracking several services.  The code is available
  16 from
  17 <a href="http://github.com/petterreinholdtsen/valutakrambod">github</a>.</p>
  18
  19 </p>There are two example clients of the library.  One is very simple and
  20 list every updated buy/sell price received from the various services.
  21 This code is started by running bin/btc-rates and call the client code
  22 in valutakrambod/client.py.  The simple client look like this:</p>
  23
  24 <p><blockquote><pre>
  25 import functools
  26 import tornado.ioloop
  27 import valutakrambod
  28 class SimpleClient(object):
  29     def __init__(self):
  30         self.services = []
  31         self.streams = []
  32         pass
  33     def newdata(self, service, pair, changed):
  34         print("%-15s %s-%s: %8.3f %8.3f" % (
  35             service.servicename(),
  36             pair[0],
  37             pair[1],
  38             service.rates[pair]['ask'],
  39             service.rates[pair]['bid'])
  40         )
  41     async def refresh(self, service):
  42         await service.fetchRates(service.wantedpairs)
  43     def run(self):
  44         self.ioloop = tornado.ioloop.IOLoop.current()
  45         self.services = valutakrambod.service.knownServices()
  46         for e in self.services:
  47             service = e()
  48             service.subscribe(self.newdata)
  49             stream = service.websocket()
  50             if stream:
  51                 self.streams.append(stream)
  52             else:
  53                 # Fetch information from non-streaming services immediately
  54                 self.ioloop.call_later(len(self.services),
  55                                        functools.partial(self.refresh, service))
  56                 # as well as regularly
  57                 service.periodicUpdate(60)
  58         for stream in self.streams:
  59             stream.connect()
  60         try:
  61             self.ioloop.start()
  62         except KeyboardInterrupt:
  63             print("Interrupted by keyboard, closing all connections.")
  64             pass
  65         for stream in self.streams:
  66             stream.close()
  67 </pre></blockquote></p>
  68
  69 <p>The library client loops over all known "public" services,
  70 initialises it, subscribes to any updates from the service, checks and
  71 activates websocket streaming if the service provide it, and if no
  72 streaming is supported, fetches information from the service and sets
  73 up a periodic update every 60 seconds.  The output from this client
  74 can look like this:</p>
  75
  76 <p><blockquote><pre>
  77 Bl3p            BTC-EUR: 5687.110 5653.690
  78 Bl3p            BTC-EUR: 5687.110 5653.690
  79 Bl3p            BTC-EUR: 5687.110 5653.690
  80 Hitbtc          BTC-USD: 6594.560 6593.690
  81 Hitbtc          BTC-USD: 6594.560 6593.690
  82 Bl3p            BTC-EUR: 5687.110 5653.690
  83 Hitbtc          BTC-USD: 6594.570 6593.690
  84 Bitstamp        EUR-USD:    1.159    1.154
  85 Hitbtc          BTC-USD: 6594.570 6593.690
  86 Hitbtc          BTC-USD: 6594.580 6593.690
  87 Hitbtc          BTC-USD: 6594.580 6593.690
  88 Hitbtc          BTC-USD: 6594.580 6593.690
  89 Bl3p            BTC-EUR: 5687.110 5653.690
  90 Paymium         BTC-EUR: 5680.000 5620.240
  91 </pre></blockquote></p>
  92
  93 <p>The exchange order book is tracked in addition to the best buy/sell
  94 price, for those that need to know the details.</p>
  95
  96 <p>The other example client is focusing on providing a curses view
  97 with updated buy/sell prices as soon as they are received from the
  98 services.  This code is located in bin/btc-rates-curses and activated
  99 by using the '-c' argument.  Without the argument the "curses" output
 100 is printed without using curses, which is useful for debugging.  The
 101 curses view look like this:</p>
 102
 103 <p><blockquote><pre>
 104            Name Pair   Bid         Ask         Spr    Ftcd    Age
 105  BitcoinsNorway BTCEUR   5591.8400   5711.0800   2.1%   16    nan     60
 106        Bitfinex BTCEUR   5671.0000   5671.2000   0.0%   16     22     59
 107         Bitmynt BTCEUR   5580.8000   5807.5200   3.9%   16     41     60
 108          Bitpay BTCEUR   5663.2700         nan   nan%   15    nan     60
 109        Bitstamp BTCEUR   5664.8400   5676.5300   0.2%    0      1      1
 110            Bl3p BTCEUR   5653.6900   5684.9400   0.5%    0    nan     19
 111        Coinbase BTCEUR   5600.8200   5714.9000   2.0%   15    nan    nan
 112          Kraken BTCEUR   5670.1000   5670.2000   0.0%   14     17     60
 113         Paymium BTCEUR   5620.0600   5680.0000   1.1%    1   7515    nan
 114  BitcoinsNorway BTCNOK  52898.9700  54034.6100   2.1%   16    nan     60
 115         Bitmynt BTCNOK  52960.3200  54031.1900   2.0%   16     41     60
 116          Bitpay BTCNOK  53477.7833         nan   nan%   16    nan     60
 117        Coinbase BTCNOK  52990.3500  54063.0600   2.0%   15    nan    nan
 118         MiraiEx BTCNOK  52856.5300  54100.6000   2.3%   16    nan    nan
 119  BitcoinsNorway BTCUSD   6495.5300   6631.5400   2.1%   16    nan     60
 120        Bitfinex BTCUSD   6590.6000   6590.7000   0.0%   16     23     57
 121          Bitpay BTCUSD   6564.1300         nan   nan%   15    nan     60
 122        Bitstamp BTCUSD   6561.1400   6565.6200   0.1%    0      2      1
 123        Coinbase BTCUSD   6504.0600   6635.9700   2.0%   14    nan    117
 124          Gemini BTCUSD   6567.1300   6573.0700   0.1%   16     89    nan
 125          Hitbtc+BTCUSD   6592.6200   6594.2100   0.0%    0      0      0
 126          Kraken BTCUSD   6565.2000   6570.9000   0.1%   15     17     58
 127   Exchangerates EURNOK      9.4665      9.4665   0.0%   16 107789    nan
 128      Norgesbank EURNOK      9.4665      9.4665   0.0%   16 107789    nan
 129        Bitstamp EURUSD      1.1537      1.1593   0.5%    4      5      1
 130   Exchangerates EURUSD      1.1576      1.1576   0.0%   16 107789    nan
 131  BitcoinsNorway LTCEUR      1.0000     49.0000  98.0%   16    nan    nan
 132  BitcoinsNorway LTCNOK    492.4800    503.7500   2.2%   16    nan     60
 133  BitcoinsNorway LTCUSD      1.0221     49.0000  97.9%   15    nan    nan
 134      Norgesbank USDNOK      8.1777      8.1777   0.0%   16 107789    nan
 135 </pre></blockquote></p>
 136
 137 <p>The code for this client is too complex for a simple blog post, so
 138 you will have to check out the git repository to figure out how it
 139 work.  What I can tell is how the three last numbers on each line
 140 should be interpreted.  The first is how many seconds ago information
 141 was received from the service.  The second is how long ago, according
 142 to the service, the provided information was updated.  The last is an
 143 estimate on how often the buy/sell values change.</p>
 144
 145 <p>If you find this library useful, or would like to improve it, I
 146 would love to hear from you.  Note that for some of the services I've
 147 implemented a trading API.  It might be the topic of a future blog
 148 post.</p>
 149
 150 <p>As usual, if you use Bitcoin and want to show your support of my
 151 activities, please send Bitcoin donations to my address
 152 <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>