Implement pair_blacklist functionality (#257)

* Adding an optional black_list of pairs not to be traded

* applying the blacklist also when not using --dynamic-whitelist

* fix error retrieving pair in conf

* Refactoring the handling of whitelist among the various functions

* unit test to verify that black listed pairs are being removed from the pair_whitelist

* Fixing newly added unit tests in develop

* fixing flake8 code review

* fix code review from @garcq

freqtrade/main.py

@@ -26,19 +26,17 @@ logger = logging.getLogger('freqtrade')
 _CONF = {}
 
 
-def refresh_whitelist(whitelist: Optional[List[str]] = None) -> None:
+def refresh_whitelist(whitelist: List[str]) -> List[str]:
     """
     Check wallet health and remove pair from whitelist if necessary
-    :param whitelist: a new whitelist (optional)
-    :return: None
+    :param whitelist: the pair the user might want to trade
+    :return: the list of pairs the user wants to trade without the one unavailable or black_listed
     """
-    whitelist = whitelist or _CONF['exchange']['pair_whitelist']
-
     sanitized_whitelist = []
     health = exchange.get_wallet_health()
     for status in health:
         pair = '{}_{}'.format(_CONF['stake_currency'], status['Currency'])
-        if pair not in whitelist:
+        if pair not in whitelist or pair in _CONF['exchange'].get('pair_blacklist', []):
             continue
         if status['IsActive']:
             sanitized_whitelist.append(pair)
@@ -47,27 +45,29 @@ def refresh_whitelist(whitelist: Optional[List[str]] = None) -> None:
                 'Ignoring %s from whitelist (reason: %s).',
                 pair, status.get('Notice') or 'wallet is not active'
             )
-    if _CONF['exchange']['pair_whitelist'] != sanitized_whitelist:
-        logger.debug('Using refreshed pair whitelist: %s ...', sanitized_whitelist)
-        _CONF['exchange']['pair_whitelist'] = sanitized_whitelist
+    return sanitized_whitelist
 
 
-def _process(dynamic_whitelist: Optional[int] = 0) -> bool:
+def _process(nb_assets: Optional[int] = 0) -> bool:
     """
     Queries the persistence layer for open trades and handles them,
     otherwise a new trade is created.
-    :param: dynamic_whitelist: True is a dynamic whitelist should be generated (optional)
+    :param: nb_assets: the maximum number of pairs to be traded at the same time
     :return: True if a trade has been created or closed, False otherwise
     """
     state_changed = False
     try:
         # Refresh whitelist based on wallet maintenance
-        refresh_whitelist(
+        sanitized_list = refresh_whitelist(
             gen_pair_whitelist(
-                _CONF['stake_currency'],
-                topn=dynamic_whitelist
-            ) if dynamic_whitelist else None
+                _CONF['stake_currency']
+            ) if nb_assets else _CONF['exchange']['pair_whitelist']
         )
+
+        # Keep only the subsets of pairs wanted (up to nb_assets)
+        final_list = sanitized_list[:nb_assets] if nb_assets else sanitized_list
+        _CONF['exchange']['pair_whitelist'] = final_list
+
         # Query trades from persistence layer
         trades = Trade.query.filter(Trade.is_open.is_(True)).all()
         if len(trades) < _CONF['max_open_trades']:
@@ -295,11 +295,10 @@ def init(config: dict, db_url: Optional[str] = None) -> None:
 
 
 @cached(TTLCache(maxsize=1, ttl=1800))
-def gen_pair_whitelist(base_currency: str, topn: int = 20, key: str = 'BaseVolume') -> List[str]:
+def gen_pair_whitelist(base_currency: str, key: str = 'BaseVolume') -> List[str]:
     """
     Updates the whitelist with with a dynamically generated list
     :param base_currency: base currency as str
-    :param topn: maximum number of returned results, must be greater than 0
     :param key: sort key (defaults to 'BaseVolume')
     :return: List of pairs
     """
@@ -309,10 +308,7 @@ def gen_pair_whitelist(base_currency: str, topn: int = 20, key: str = 'BaseVolum
         reverse=True
     )
 
-    if topn <= 0:
-        topn = 20
-
-    return [s['MarketName'].replace('-', '_') for s in summaries[:topn]]
+    return [s['MarketName'].replace('-', '_') for s in summaries]
 
 
 def cleanup() -> None:

freqtrade/misc.py

@@ -268,6 +268,14 @@ CONF_SCHEMA = {
                         'pattern': '^[0-9A-Z]+_[0-9A-Z]+$'
                     },
                     'uniqueItems': True
+                },
+                'pair_blacklist': {
+                    'type': 'array',
+                    'items': {
+                        'type': 'string',
+                        'pattern': '^[0-9A-Z]+_[0-9A-Z]+$'
+                    },
+                    'uniqueItems': True
                 }
             },
             'required': ['name', 'key', 'secret', 'pair_whitelist']

freqtrade/tests/test_acl_pair.py

@@ -41,12 +41,10 @@ def test_refresh_whitelist(mocker):
     mocker.patch.dict('freqtrade.main._CONF', conf)
     mocker.patch.multiple('freqtrade.main.exchange',
                           get_wallet_health=get_health)
-    # no argument: use the whitelist provided by config
-    refresh_whitelist()
+    refreshedwhitelist = refresh_whitelist(conf['exchange']['pair_whitelist'])
     whitelist = ['BTC_ETH', 'BTC_TKN']
-    pairslist = conf['exchange']['pair_whitelist']
     # Ensure all except those in whitelist are removed
-    assert set(whitelist) == set(pairslist)
+    assert set(whitelist) == set(refreshedwhitelist)
 
 
 def test_refresh_whitelist_dynamic(mocker):
@@ -56,9 +54,8 @@ def test_refresh_whitelist_dynamic(mocker):
                           get_wallet_health=get_health)
     # argument: use the whitelist dynamically by exchange-volume
     whitelist = ['BTC_ETH', 'BTC_TKN']
-    refresh_whitelist(whitelist)
-    pairslist = conf['exchange']['pair_whitelist']
-    assert set(whitelist) == set(pairslist)
+    refreshedwhitelist = refresh_whitelist(whitelist)
+    assert set(whitelist) == set(refreshedwhitelist)
 
 
 def test_refresh_whitelist_dynamic_empty(mocker):

freqtrade/tests/test_main.py

@@ -180,6 +180,23 @@ def test_create_trade_no_pairs(default_conf, ticker, mocker):
         create_trade(default_conf['stake_amount'])
 
 
+def test_create_trade_no_pairs_after_blacklist(default_conf, ticker, mocker):
+    mocker.patch.dict('freqtrade.main._CONF', default_conf)
+    mocker.patch('freqtrade.main.get_signal', side_effect=lambda s, t: True)
+    mocker.patch.multiple('freqtrade.rpc', init=MagicMock(), send_msg=MagicMock())
+    mocker.patch.multiple('freqtrade.main.exchange',
+                          validate_pairs=MagicMock(),
+                          get_ticker=ticker,
+                          buy=MagicMock(return_value='mocked_limit_buy'))
+
+    with pytest.raises(DependencyException, match=r'.*No pair in whitelist.*'):
+        conf = copy.deepcopy(default_conf)
+        conf['exchange']['pair_whitelist'] = ["BTC_ETH"]
+        conf['exchange']['pair_blacklist'] = ["BTC_ETH"]
+        mocker.patch.dict('freqtrade.main._CONF', conf)
+        create_trade(default_conf['stake_amount'])
+
+
 def test_handle_trade(default_conf, limit_buy_order, limit_sell_order, mocker):
     mocker.patch.dict('freqtrade.main._CONF', default_conf)
     mocker.patch('freqtrade.main.get_signal', side_effect=lambda s, t: True)