複数のCSVファイルに対して、同一アイテムの数値を加算する

import argparse
import csv
import os


def main() -> None:

    parser = argparse.ArgumentParser()
    parser.add_argument("-i", "--input_dir_path", default="./")
    parser.add_argument("-o", "--output_file_path", default="./output.csv")
    args = parser.parse_args()

    input_dir_path = args.input_dir_path
    output_file_path = args.output_file_path

    csv_files = [file for file in os.listdir(input_dir_path) if file.endswith(".csv")]
    margede_data = {}

    # csvの読み込み
    for csv_file in csv_files:
        with open(csv_file, "r", encoding="utf-8") as read_file:
            reader = csv.reader(read_file, delimiter=",")

            for data in reader:
                if data[0] in margede_data:
                    margede_data[data[0]] += int(data[1])
                else:
                    margede_data[data[0]] = int(data[1])

    # マージ後データのcsv出力
    with open(output_file_path, "w", encoding="utf-8", newline="") as write_file:
        writer = csv.writer(write_file, delimiter=",")

        for jancode, sales_volume in margede_data.items():
            writer.writerow([jancode, sales_volume])


if __name__ == "__main__":
    main()