use Type Alias for Ticker result to improve keyerror resiliancy

freqtrade/exchange/exchange.py

@@ -31,6 +31,7 @@ from freqtrade.exceptions import (DDosProtection, ExchangeError, InsufficientFun
 from freqtrade.exchange.common import (API_FETCH_ORDER_RETRY_COUNT, BAD_EXCHANGES,
                                        EXCHANGE_HAS_OPTIONAL, EXCHANGE_HAS_REQUIRED,
                                        remove_credentials, retrier, retrier_async)
+from freqtrade.exchange.types import Tickers
 from freqtrade.misc import (chunks, deep_merge_dicts, file_dump_json, file_load_json,
                             safe_value_fallback2)
 from freqtrade.plugins.pairlist.pairlist_helpers import expand_pairlist
@@ -1420,14 +1421,15 @@ class Exchange:
             raise OperationalException(e) from e
 
     @retrier
-    def get_tickers(self, symbols: Optional[List[str]] = None, cached: bool = False) -> Dict:
+    def get_tickers(self, symbols: Optional[List[str]] = None, cached: bool = False) -> Tickers:
         """
         :param cached: Allow cached result
         :return: fetch_tickers result
         """
+        tickers: Tickers
         if cached:
             with self._cache_lock:
-                tickers = self._fetch_tickers_cache.get('fetch_tickers')
+                tickers = self._fetch_tickers_cache.get('fetch_tickers')  # type: ignore
             if tickers:
                 return tickers
         try:

freqtrade/exchange/kraken.py

@@ -12,6 +12,7 @@ from freqtrade.exceptions import (DDosProtection, InsufficientFundsError, Invali
                                   OperationalException, TemporaryError)
 from freqtrade.exchange import Exchange
 from freqtrade.exchange.common import retrier
+from freqtrade.exchange.types import Tickers
 
 
 logger = logging.getLogger(__name__)
@@ -45,7 +46,7 @@ class Kraken(Exchange):
         return (parent_check and
                 market.get('darkpool', False) is False)
 
-    def get_tickers(self, symbols: Optional[List[str]] = None, cached: bool = False) -> Dict:
+    def get_tickers(self, symbols: Optional[List[str]] = None, cached: bool = False) -> Tickers:
         # Only fetch tickers for current stake currency
         # Otherwise the request for kraken becomes too large.
         symbols = list(self.get_markets(quote_currencies=[self._config['stake_currency']]))

freqtrade/exchange/types.py

@@ -0,0 +1,5 @@
+from typing import Any, Dict
+
+
+Ticker = Dict[str, Any]
+Tickers = Dict[str, Ticker]