Average stock price calculator with LIFO strategy

ade-calc.py

#!/usr/bin/env python3.10

import csv
import argparse
from collections import defaultdict

BUY = "Buy"
SELL = "Sell"

class Transaction:
    def __init__(self, shares, price):
        self.shares = shares
        self.price = price

def calculate_lifo_average(transactions):
    portfolios = defaultdict(list)

    def average_price(stock):
        purchases = portfolios[stock]
        total_cost = sum(purchase.shares * purchase.price for purchase in purchases)
        total_shares = sum(purchase.shares for purchase in purchases)
        average_price = total_cost / total_shares if total_shares > 0 else 0
        return average_price

    for transaction in reversed(transactions):
        stock = transaction['stock']
        if transaction['type'] == BUY:
            portfolios[stock].append(Transaction(transaction['shares'], transaction['price']))
        elif transaction['type'] == SELL:
            print(f"{transaction['date']}: [{stock}] Average stock price before Sell: {average_price(stock):.4f} EUR")
            shares_to_sell = transaction['shares']
            while shares_to_sell > 0 and portfolios[stock]:
                top = portfolios[stock][-1]
                if top.shares <= shares_to_sell:
                    shares_to_sell -= top.shares
                    portfolios[stock].pop()
                else:
                    top.shares -= shares_to_sell
                    shares_to_sell = 0
                    
            print(f"{transaction['date']}: [{stock}] Average stock price after Sell: {average_price(stock):.4f} EUR")

def read_transactions_from_csv(file_path):
    transactions = []
    with open(file_path, mode='r') as file:
        reader = csv.DictReader(file)
        for row in reader:
            transaction = {
                'date': row[reader.fieldnames[0]],
                'stock': row['Symbol'],
                'type': row['Type'],
                'shares': float(row['Quantity']),
                'price': float(row['Price'])
            }
            transactions.append(transaction)
    return transactions

def main():
    parser = argparse.ArgumentParser(description='Calculate stocks average buying price.')
    parser.add_argument('file_path', type=str, help='The CSV transactions file path')
    args = parser.parse_args()

    # read transactions from CSV file
    transactions = read_transactions_from_csv(args.file_path)

    # calculate and print average stock price before and after each Sell operation
    calculate_lifo_average(transactions)

if __name__ == '__main__':
    main()