如何将用户输入添加到列表中并能够看到它？

Question

I am trying to make a sign up system in python 3.7 but I don't know how to permanently add a users login to a list and not having to sign up for the same account every time you open the program.

I was not able to make up a solution to this problem.

Usernames = ['User1', 'User2']
Passwords = ['password123', 'password123']


print('Type SU to Sign Up or type LI to Log In!')
UOption = input('Option>> ')

if UOption == 'SU':
    SI = True
    LI = False
    if SI == True:
        print('Signing Up!')
        SUUsername = input('Username>> ')
        SUEmail = input('Email>> ')
        SUPassword = input('Password>> ')

    Usernames.append(SUUsername)
    Emails.append(SUEmail)
    Passwords.append(SUPassword)
    LI = True
    SI = False

I am expecting when I get this working that the user will be able to sign up once then be able to log in if they reopen the program without having to sign up again.

Answer 1

You could use the pickle module:

Firstly, to create the necessary files, run the following code in the folder that your program is saved in:

import pickle
pickle.dump([],open("usernames.dat","wb"))
pickle.dump([],open("emails.dat","wb"))
pickle.dump([],open("passwords.dat","wb"))

In your program, add:

import pickle

at the start of the program

Replace the lines:

Usernames = ['User1', 'User2']
Emails = ['Email1', 'Email2'] # I'm assuming this line has just been missed off your question
Passwords = ['password123', 'password123']

With:

Usernames = pickle.load(open("usernames.dat","rb"))
Emails = pickle.load(open("emails.dat","rb"))
Passwords = pickle.load(open("passwords.dat","rb"))

To read from the files

And finally add these lines at the end of your program to update the files with the new user's details

pickle.dump(Usernames,open("usernames.dat","wb"))
pickle.dump(Emails,open("emails.dat","wb"))
pickle.dump(Passwords,open("passwords.dat","wb"))

This is a link to more details on how to use pickles, if your interested

https://www.tutorialspoint.com/python-pickling

For source code including these edits see here:

https://pastebin.com/H4ryP6cT