Don't remove elements from list we're iterating over

closes #9127

freqtrade/plugins/pairlist/pairlist_helpers.py

@@ -29,9 +29,8 @@ def expand_pairlist(wildcardpl: List[str], available_pairs: List[str],
             except re.error as err:
                 raise ValueError(f"Wildcard error in {pair_wc}, {err}")
 
-        for element in result:
-            if not re.fullmatch(r'^[A-Za-z0-9:/-]+$', element):
-                result.remove(element)
+        result = [element for element in result if re.fullmatch(r'^[A-Za-z0-9:/-]+$', element)]
+
     else:
         for pair_wc in wildcardpl:
             try:

tests/plugins/test_pairlist.py

@@ -1373,6 +1373,9 @@ def test_expand_pairlist(wildcardlist, pairs, expected):
     (['BTC/USDT:USDT'],
      ['BTC/USDT:USDT', 'BTC/USDT'],
      ['BTC/USDT:USDT']),
+    (['BB_BTC/USDT', 'CC_BTC/USDT', 'AA_ETH/USDT', 'XRP/USDT', 'ETH/USDT', 'XX_BTC/USDT'],
+     ['BTC/USDT', 'ETH/USDT'],
+     ['XRP/USDT', 'ETH/USDT']),
 ])
 def test_expand_pairlist_keep_invalid(wildcardlist, pairs, expected):
     if expected is None: