Add cache for expanded_blacklist() in PairListManager in backtest mode

freqtrade/plugins/pairlistmanager.py

@@ -5,7 +5,7 @@ PairList manager class
 import logging
 from functools import partial
 
-from cachetools import TTLCache, cached
+from cachetools import LRUCache, TTLCache, cached
 
 from freqtrade.constants import Config, ListPairsWithTimeframes
 from freqtrade.data.dataprovider import DataProvider
@@ -56,6 +56,7 @@ class PairListManager(LoggingMixin):
             )
 
         self._check_backtest()
+        self._not_expiring_cache: LRUCache = LRUCache(maxsize=1)
 
         refresh_period = config.get("pairlist_refresh_period", 3600)
         LoggingMixin.__init__(self, logger, refresh_period)
@@ -109,7 +110,15 @@ class PairListManager(LoggingMixin):
     @property
     def expanded_blacklist(self) -> list[str]:
         """The expanded blacklist (including wildcard expansion)"""
-        return expand_pairlist(self._blacklist, self._exchange.get_markets().keys())
+        eblacklist = self._not_expiring_cache.get("eblacklist")
+
+        if not eblacklist:
+            eblacklist = expand_pairlist(self._blacklist, self._exchange.get_markets().keys())
+
+            if self._config["runmode"] in (RunMode.BACKTEST, RunMode.HYPEROPT):
+                self._not_expiring_cache["eblacklist"] = eblacklist.copy()
+
+        return eblacklist
 
     @property
     def name_list(self) -> list[str]: