有很多错误，所以我将使用注解来解释更改：

# 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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我会这样做：

# 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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修正了我代码中的一个问题，但又出现了另一个问题。

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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