Introduce chainable PairlistFilters

freqtrade/resolvers/pairlistfilter_resolver.py

@@ -0,0 +1,53 @@
+# pragma pylint: disable=attribute-defined-outside-init
+
+"""
+This module load custom pairlists
+"""
+import logging
+from pathlib import Path
+
+from freqtrade import OperationalException
+from freqtrade.pairlist.IPairListFilter import IPairListFilter
+from freqtrade.resolvers import IResolver
+
+logger = logging.getLogger(__name__)
+
+
+class PairListFilterResolver(IResolver):
+    """
+    This class contains all the logic to load custom PairList class
+    """
+
+    __slots__ = ['pairlistfilter']
+
+    def __init__(self, pairlist_name: str, freqtrade, config: dict) -> None:
+        """
+        Load the custom class from config parameter
+        :param config: configuration dictionary or None
+        """
+        self.pairlistfilter = self._load_pairlist(pairlist_name, config,
+                                                  kwargs={'freqtrade': freqtrade,
+                                                          'config': config})
+
+    def _load_pairlist(
+            self, pairlistfilter_name: str, config: dict, kwargs: dict) -> IPairListFilter:
+        """
+        Search and loads the specified pairlist.
+        :param pairlistfilter_name: name of the module to import
+        :param config: configuration dictionary
+        :param extra_dir: additional directory to search for the given pairlist
+        :return: PairList instance or None
+        """
+        current_path = Path(__file__).parent.parent.joinpath('pairlist').resolve()
+
+        abs_paths = self.build_search_paths(config, current_path=current_path,
+                                            user_subdir=None, extra_dir=None)
+
+        pairlist = self._load_object(paths=abs_paths, object_type=IPairListFilter,
+                                     object_name=pairlistfilter_name, kwargs=kwargs)
+        if pairlist:
+            return pairlist
+        raise OperationalException(
+            f"Impossible to load PairlistFilter '{pairlistfilter_name}'. This class does not exist "
+            "or contains Python code errors."
+        )