refactor: Update position calculator with dynamic account size and automatic stop loss

src/trading/main.py

@@ -2,10 +2,20 @@ from datetime import datetime
 from position_calculator import PositionCalculator
 from portfolio import Portfolio, Position
 
+def get_float_input(prompt: str) -> float:
+    while True:
+        try:
+            return float(input(prompt))
+        except ValueError:
+            print("Please enter a valid number")
+
 def main():
+    # Get initial portfolio value from user
+    portfolio_value = get_float_input("Enter your portfolio value: $")
+    
     # Initialize portfolio and position calculator
     portfolio = Portfolio()
-    calculator = PositionCalculator(account_size=100000)  # $100k account
+    calculator = PositionCalculator(account_size=portfolio_value)  # Use user's portfolio value
     
     while True:
         print("\nTrading Management System")
@@ -19,16 +29,15 @@ def main():
         
         if choice == "1":
             try:
-                entry_price = float(input("Enter entry price: "))
-                stop_loss = float(input("Enter stop loss price: "))
+                entry_price = get_float_input("Enter entry price: $")
                 
-                position = calculator.calculate_position_size(entry_price, stop_loss)
+                position = calculator.calculate_position_size(entry_price)
                 
                 print("\nPosition Details:")
                 print(f"Shares: {position['shares']}")
                 print(f"Position Value: ${position['position_value']:.2f}")
                 print(f"Risk Amount: ${position['risk_amount']:.2f}")
-                print(f"Risk Per Share: ${position['risk_per_share']:.2f}")
+                print(f"Stop Loss Price: ${position['stop_loss']:.2f}")
                 
             except ValueError as e:
                 print(f"Error: {e}")
@@ -36,10 +45,10 @@ def main():
         elif choice == "2":
             try:
                 symbol = input("Enter symbol: ")
-                entry_price = float(input("Enter entry price: "))
+                entry_price = float(input("Enter entry price: $"))
                 shares = int(input("Enter number of shares: "))
-                stop_loss = float(input("Enter stop loss: "))
-                target_price = float(input("Enter target price: "))
+                stop_loss = entry_price * 0.94  # Automatic 6% stop loss
+                target_price = float(input("Enter target price: $"))
                 
                 position = Position(
                     symbol=symbol,

src/trading/position_calculator.py

@@ -1,26 +1,30 @@
 class PositionCalculator:
-    def __init__(self, account_size: float, risk_percentage: float = 1.0):
+    def __init__(self, account_size: float, risk_percentage: float = 1.0, stop_loss_percentage: float = 6.0):
         """
         Initialize position calculator with account size and risk percentage
         
         Args:
             account_size (float): Total trading account value
             risk_percentage (float): Maximum risk per trade as percentage (default 1%)
+            stop_loss_percentage (float): Stop loss percentage (default 6%)
         """
         self.account_size = account_size
         self.risk_percentage = risk_percentage / 100.0  # Convert to decimal
+        self.stop_loss_percentage = stop_loss_percentage / 100.0  # Convert to decimal
         
-    def calculate_position_size(self, entry_price: float, stop_loss: float) -> dict:
+    def calculate_position_size(self, entry_price: float) -> dict:
         """
         Calculate position size based on risk parameters
         
         Args:
             entry_price (float): Planned entry price
-            stop_loss (float): Stop loss price
             
         Returns:
             dict: Position details including shares and dollar amounts
         """
+        # Calculate stop loss price (6% below entry)
+        stop_loss = entry_price * (1 - self.stop_loss_percentage)
+        
         # Calculate risk amount in dollars
         risk_amount = self.account_size * self.risk_percentage
         
@@ -40,5 +44,6 @@ class PositionCalculator:
             "shares": shares,
             "position_value": position_value,
             "risk_amount": risk_amount,
-            "risk_per_share": risk_per_share
+            "risk_per_share": risk_per_share,
+            "stop_loss": stop_loss
         }