03_functions.py

"""
03_functions.py
----------------
Concept: Functions
Context: Reusable code for calculating position sizes and PnL.

Functions allow you to write logic once and reuse it multiple times.
"""

# 1. Simple Function
def calculate_pnl(entry_price, exit_price, position_size):
    """
    Calculates Profit and Loss (PnL).
    PnL = (Exit - Entry) * Size
    """
    diff = exit_price - entry_price
    pnl = diff * position_size
    return pnl

# 2. Function with Default Arguments
def get_fee(trade_amount, fee_rate=0.001):
    """
    Calculates trading fee. Default fee rate is 0.1% (0.001).
    """
    return trade_amount * fee_rate

# 3. Main Logic
def main():
    # Scenario 1: Quick Scalp
    entry = 50000
    exit_p = 50500
    size = 0.1 # BTC
    
    profit = calculate_pnl(entry, exit_p, size)
    print(f"Trade 1 PnL: ${profit}")
    
    # Scenario 2: Swing Trade
    entry_2 = 48000
    exit_2 = 52000
    size_2 = 0.5
    
    profit_2 = calculate_pnl(entry_2, exit_2, size_2)
    print(f"Trade 2 PnL: ${profit_2}")
    
    # Checking Fees
    trade_value = entry * size # 50000 * 0.1 = 5000
    fee_standard = get_fee(trade_value) # Uses default 0.1%
    fee_vip = get_fee(trade_value, fee_rate=0.0005) # VIP rate 0.05%
    
    print(f"\nFee (Standard): ${fee_standard}")
    print(f"Fee (VIP): ${fee_vip}")

# Best practice: Execute main() only if script is run directly
if __name__ == "__main__":
    main()