text: # -*- coding: utf-8 -*-
  
  import os
  import sys
  import time
  
  # -----------------------------------------------------------------------------
  
  root = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
  sys.path.append(root + '/python')
  
  # -----------------------------------------------------------------------------
  
  import ccxt  # noqa: E402
  
  # -----------------------------------------------------------------------------
  # common constants
  
  msec = 1000
  minute = 60 * msec
  hold = 30
  
  # -----------------------------------------------------------------------------
  
  exchange = ccxt.bitfinex()
  
  # -----------------------------------------------------------------------------
  
  from_datetime = '2017-01-01 00:00:00'
  from_timestamp = exchange.parse8601(from_datetime)
  
  # -----------------------------------------------------------------------------
  
  now = exchange.milliseconds()
  
  # -----------------------------------------------------------------------------
  
  data = []
  
  while from_timestamp < now:
  
      try:
  
          print(exchange.milliseconds(), 'Fetching candles starting from', exchange.iso8601(from_timestamp))
          ohlcvs = exchange.fetch_ohlcv('BTC/USD', '5m', from_timestamp)
          print(exchange.milliseconds(), 'Fetched', len(ohlcvs), 'candles')
          if len(ohlcvs) > 0:
              first = ohlcvs[0][0]
              last = ohlcvs[-1][0]
              print('First candle epoch', first, exchange.iso8601(first))
              print('Last candle epoch', last, exchange.iso8601(last))
              # from_timestamp += len(ohlcvs) * minute * 5  # very bad
              from_timestamp = ohlcvs[-1][0] + minute * 5  # good
              data += ohlcvs
  
      except (ccxt.ExchangeError, ccxt.AuthenticationError, ccxt.ExchangeNotAvailable, ccxt.RequestTimeout) as error:
  
          print('Got an error', type(error).__name__, error.args, ', retrying in', hold, 'seconds...')
          time.sleep(hold)
  