Implement strategy-controlled stake sizes. Expose self.wallet to a strategy.

freqtrade/strategy/interface.py

@@ -304,6 +304,23 @@ class IStrategy(ABC, HyperStrategyMixin):
         """
         return None
 
+    def custom_stake_amount(self, pair: str, current_time: datetime, current_rate: float,
+                            proposed_stake: float, min_stake: float, max_stake: float,
+                            **kwargs) -> float:
+        """
+        Customize stake size for each new trade. This method is not called when edge module is
+        enabled.
+
+        :param pair: Pair that's currently analyzed
+        :param current_time: datetime object, containing the current datetime
+        :param current_rate: Rate, calculated based on pricing settings in ask_strategy.
+        :param proposed_stake: A stake amount proposed by the bot.
+        :param min_stake: Minimal stake size allowed by exchange.
+        :param max_stake: Balance available for trading.
+        :return: A stake size, which is between min_stake and max_stake.
+        """
+        return proposed_stake
+
     def informative_pairs(self) -> ListPairsWithTimeframes:
         """
         Define additional, informative pair/interval combinations to be cached from the exchange.