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I'm currently using JSON to make a username/password program but I have a problem with duplicate accounts. I tried to code a way to prevent users from creating usernames that the JSON database already contains, but it doesn't quite work.

Problems:

  • Asks for the username, doesn't ask for the password even when the file tried is empty

  • Sometimes says the username already exists, but creates the account duplicate anyway.

What I want the program to do:

  • Ask for the new username/password
  • If the username is unique, place the new account in the file
  • If the username is already owned, don't add the new account and go to the start of the function.

How would I do this efficiently? This is the code I've tried, but the problems I mentioned make it invalid

def createUser():
    global accounts
    nUsername = input("Create Username »  ")
    for item in accounts:
        if item[0] == nUsername:
            return "Already Exsists!"
        else:
            nPassword = input("Create Password » ")
            entry = [nUsername, nPassword]
            accounts.append(entry)
            accounts = accounts[:500000]
            autoSave()

For anyone wondering, this is what the autosave() function is:

def autoSave():
    with open("Accounts.json", "w") as outfile:
        json.dump(accounts, outfile)

And this is what the inside of the JSON file looks like:

[["ExampleUsername", "BadPasswrdo14130"]]
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3 Answers 3

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2

There is many mistakes so I will use comment to explain changes:

# you file containt utf8 chars, you need to specify encoding
# coding=utf-8

import os
import json

# I use a dict structure instead of a list for easier retrieval
# you can easily see if an account exist and get its password
# also global keyword is to avoid, so prefer declaring in the global context instead of pushing to the global context
accounts = {}

# if we have a file, deserialize content
if os.path.exists("/tmp/Accounts.json"):
    try:
        with open("/tmp/Accounts.json") as f:
            accounts = dict(json.loads(f.read()))
    except:
        pass

def createUser():
    # input is equivalent to eval(raw_input(... which is not the goal here
    nUsername = raw_input("Create Username »  ")

    # with a dict, no need to iterate through, simply use `in`
    if nUsername in accounts.keys():
        return createUser()

    nPassword = raw_input("Create Password » ")
    # this is how you assign the new account
    accounts[nUsername] = nPassword
    autoSave()

def autoSave():
    with open("/tmp/Accounts.json", "w") as outfile:
        # we convert here the dict to your list structure
        json.dump(list(accounts.iteritems()), outfile)

def existingUser():
    eUsername = raw_input("Your Username » ")
    ePassword = raw_input("Your Password » ")

    for item in accounts:
        if eUsername in accounts and accounts[eUsername] == ePassword:
            return 'Processing Sucessfully logged into your account!'
        else:
            return "Login failed"

createUser()
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8 Comments

This works! Only one problem, when a new account is created the JSON file is replaced with only that new account, it doesent contain any others. In other words, its only allowing one account?
Edit: Mistake on my part. Fixed
I also edit to save as a json list, so it looks like what you expect.
I don't think you fixed the problem. JSON supports dict-like structures so I don't see why you would need to convert it into a list. But I think you need to import the file at the beginning of your script instead of initializing an empty dict (accounts = {}).
I will add an edit to allow retrieval of serialized accounts.
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I would do it this way:

# This function will help us to check if the user already exists
def alreadyExist(nUsername):
    global accounts
    for account in accounts:
        if account[0] == nUsername
            return True
    return False


def createUser():
    global accounts

    # We declarate nUsername first as None
    nUsername = None

    # While the username exists, we have to ask the user for the username
    while not nUsername or alreadyExist(nUsername):
        nUsername = input("Create Username »  ")

    # We are out of the bucle. The username doesn't exist, we can ask for the password
    nPassword = input("Create Password » ")
    entry = [nUsername, nPassword]
    accounts.append(entry)
    accounts = accounts[:500000]
    autoSave()
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1 Comment

Tried this.. Doesen't end. Repeats asking for nUsername + nPassword. Does create the account in the file though. Also doesent prevent dups.
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Fixed one issue of my code, but made another. This section was working fine before the chances from @CyrBill

def existingUser():
eUsername = input("Your Username » ")
ePassword = input("Your Password » ")

for item in accounts: #no need for braces
    if item[0] == eUsername and item[1] == ePassword:
        return 'Processing Sucessfully logged into your account!'
    else:
        return "Login failed"
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4 Comments

I edit my answer, avoid reply to your question with another question. Prefer editing your post or, better, creating a new one.
Oh, and you misspelled my name ! :(
Sorry about your name! xD. Thanks, though. Code's working perfect now.
Still misspelled, If we are done with your problem, please accept an answer to close the topic.

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