如何阻止csv文件覆盖

Question

此代码要求用户输入条形码，然后我的程序打开一个csv文件并访问一个数据库，有4种不同的产品，用户会输入他们想要的产品数量，然后询问他们是否要继续购物或按0并停止购物并打印收据（这是另一个csv文件），我的问题是我的程序不考虑以前的订单，只有最后一个，如果这是有道理的（如果我订购3个西红柿然后4芹菜片只考虑芹菜的量）。我想为可怜的英语辩护，因为它不是我的主要语言。以下是我认为出错的代码部分

def quantity():
    fileOne = open('receipt.csv', 'w')
    writer = csv.writer(fileOne)
    global total_price
    product_data = read_csv_file()
    matches = search_user_input(product_data)
    if matches: # Will not be True if search_user_input returned None
        print("apple")
        product, price = matches[0], matches[1]
        order = int(input("How much of {} do you want?".format(product)))
        values = [str(product), str(price), str(order*price)]
        writer.writerows((values,))
        total_price.append(order * price)
    continue_shopping=int(input("press 0 to stop shopping and print your reciept or press 1 to continue shopping"))
    if (continue_shopping == 0):
        fileOne.close()
        fileTwo = open("receipt.csv" , "r")
        reader = csv.reader(fileTwo)
        for row in reader:
            if row != None:
                print(row)
    elif continue_shopping==1:
        quantity()

quantity()

如果你很好奇，这是代码的其余部分。

import csv 
import locale

total_price = []

locale.setlocale( locale.LC_ALL, '' )
def read_csv_file():
    global total_price
    """ reads csv data and appends each row to list """
    csv_data = []
    with open("task2.csv") as csvfile:
         spamreader = csv.reader(csvfile, delimiter=",", quotechar="|")
         for row in spamreader:
             csv_data.append(row)
    return csv_data


def get_user_input():
    global total_price
    """ get input from user """
    while True:
        try:
            GTIN = int(input("input your gtin-8 number: "))
            return GTIN # Breaks the loop and returns the value
        except:
            print ("Oops! That was not a valid number.  Try again")


def search_user_input(product_data):
    global total_price
    repeat=""
    # Pass the csv data as an argument
    """ search csv data for string """
    keep_searching = True

    while keep_searching:
        gtin = get_user_input()
        for row in product_data:
            if row[0] == str(gtin):
                product = row[1]
                price = round(float(row[2]),2)
                return(product, price)
        while True:
            try:
                repeat = input("not in there? search again? If so (y), else press enter to continue")
                break
            except:
                print("please make sure you enter a valid string") 
        if repeat != 'y':
            keep_searching = False 
            return None 


def quantity():
    fileOne = open('receipt.csv', 'w')
    writer = csv.writer(fileOne)
    global total_price
    product_data = read_csv_file()
    matches = search_user_input(product_data)
    if matches: # Will not be True if search_user_input returned None
        print("apple")
        product, price = matches[0], matches[1]
        order = int(input("How much of {} do you want?".format(product)))
        values = [str(product), str(price), str(order*price)]
        writer.writerows((values,))
        total_price.append(order * price)
    continue_shopping=int(input("press 0 to stop shopping and print your reciept or press 1 to continue shopping"))
    if (continue_shopping == 0):
        fileOne.close()
        fileTwo = open("receipt.csv" , "r")
        reader = csv.reader(fileTwo)
        for row in reader:
            if row != None:
                print(row)
    elif continue_shopping==1:
        quantity()

quantity()

我感谢任何帮助或建议，或者如果您不理解我的代码的一部分，我可以尝试解释