如何覆盖txt文件名中的信息已经存在

问：

我有一个程序，可以为您放置的任何网站创建一个随机生成的密码。如果可能的话，我想要的是，如果用户输入Amazon并输出密码，然后再次输入Amazon，它不会在文本文件中复制Amazon，而是使用新密码更新以前输入的密码。我不确定这是否可能，或者它是否总是附加到我的列表中。

import random
import string
# name of website we're creating the password for
website = input("What website are you creating a password for? ").capitalize()
def char_length():
    # makes it so this part will repeat
    while True:
        length = input("How many characters would you like your password to be? ")
        if length.isdigit() and 0 < int(length) < 51:
            return int(length)
        else:
            print('Response must be a number between 0 and 50')

def random_pass(length):
    while True:
        spec_char = input("Would you like special characters in your password y/n? ").lower()
        if spec_char == "y":
            characters =  string.ascii_letters + string.digits + string.punctuation
            password = ''.join(random.choice(characters) for i in range(length))
            print("Your password for", website, "is:", password)
            return password
        elif spec_char == "n":
            characters = ''.join(random.choice(string.ascii_letters) for i in range(length))
            print("Your password for", website, "is:", characters)
            return characters
        else:
            print("Please only type 'Yes' or 'No'.")

random_pass(char_length())

file = open("password.txt", "a+")
webname = file.write(website)
file.write(": ")
new_pass = file.write(random_pass(char_length()))
file.write("\n")
print(webname)
print(new_pass)
file.close()

我自己尝试过几种不同的方式，但我只学习了一个月 python，所以我不知道该如何解决这个问题。