qt utxo list: spend_list is now a set (and renamed)

this is a small performance improvement ("if x in spend_list" was linear)
and the "order" of selected coins does not matter anyway

electrum/gui/qt/utxo_list.py

@@ -23,7 +23,7 @@
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-from typing import Optional, List, Dict, Sequence
+from typing import Optional, List, Dict, Sequence, Set
 from enum import IntEnum
 
 from PyQt5.QtCore import Qt
@@ -58,7 +58,7 @@ class UTXOList(MyTreeView):
         super().__init__(parent, self.create_menu,
                          stretch_column=self.Columns.LABEL,
                          editable_columns=[])
-        self.spend_list = []  # type: Sequence[str]
+        self._spend_set = set()  # type: Set[str]  # coins selected by the user to spend from
         self.setModel(QStandardItemModel(self))
         self.setSelectionMode(QAbstractItemView.ExtendedSelection)
         self.setSortingEnabled(True)
@@ -75,12 +75,12 @@ class UTXOList(MyTreeView):
             self.insert_utxo(idx, utxo)
         self.filter()
         # update coincontrol status bar
-        coins = [self.utxo_dict[x] for x in self.spend_list] or utxos
+        coins = [self.utxo_dict[x] for x in self._spend_set] or utxos
         coins = self._filter_frozen_coins(coins)
         amount = sum(x.value_sats() for x in coins)
         amount_str = self.parent.format_amount_and_units(amount)
         num_outputs_str = _("{} outputs available ({} total)").format(len(coins), len(utxos))
-        if self.spend_list:
+        if self._spend_set:
             self.parent.set_coincontrol_msg(_("Coin control active") + f': {num_outputs_str}, {amount_str}')
         else:
             self.parent.set_coincontrol_msg(None)
@@ -101,7 +101,7 @@ class UTXOList(MyTreeView):
         utxo_item[self.Columns.OUTPOINT].setFont(QFont(MONOSPACE_FONT))
         utxo_item[self.Columns.ADDRESS].setData(name, Qt.UserRole)
         SELECTED_TO_SPEND_TOOLTIP = _('Coin selected to be spent')
-        if name in self.spend_list:
+        if name in self._spend_set:
             for col in utxo_item:
                 col.setBackground(ColorScheme.GREEN.as_color(True))
                 if col != self.Columns.OUTPOINT:
@@ -113,7 +113,7 @@ class UTXOList(MyTreeView):
             utxo_item[self.Columns.OUTPOINT].setBackground(ColorScheme.BLUE.as_color(True))
             utxo_item[self.Columns.OUTPOINT].setToolTip(f"{name}\n{_('Coin is frozen')}")
         else:
-            tooltip = ("\n" + SELECTED_TO_SPEND_TOOLTIP) if name in self.spend_list else ""
+            tooltip = ("\n" + SELECTED_TO_SPEND_TOOLTIP) if name in self._spend_set else ""
             utxo_item[self.Columns.OUTPOINT].setToolTip(name + tooltip)
         self.model().insertRow(idx, utxo_item)
 
@@ -133,17 +133,17 @@ class UTXOList(MyTreeView):
 
     def set_spend_list(self, coins: List[PartialTxInput]):
         coins = self._filter_frozen_coins(coins)
-        self.spend_list = [utxo.prevout.to_str() for utxo in coins]
+        self._spend_set = {utxo.prevout.to_str() for utxo in coins}
         self.update()
 
     def get_spend_list(self) -> Sequence[PartialTxInput]:
-        return [self.utxo_dict[x] for x in self.spend_list]
+        return [self.utxo_dict[x] for x in self._spend_set]
 
     def _maybe_reset_spend_list(self, current_wallet_utxos: Sequence[PartialTxInput]) -> None:
         # if we spent one of the selected UTXOs, just reset selection
         utxo_set = {utxo.prevout.to_str() for utxo in current_wallet_utxos}
-        if not all([prevout_str in utxo_set for prevout_str in self.spend_list]):
+        if not all([prevout_str in utxo_set for prevout_str in self._spend_set]):
-            self.spend_list = []
+            self._spend_set = set()
 
     def create_menu(self, position):
         selected = self.get_selected_outpoints()