How can I save input to a file and then check the input from the file?

Question

I'm trying to create a VERY basic little operating system just for fun, using Python. So far I have this:

rUsername = input("Create a new user: ")
rPassword = input("Create a password for the user: ")
tUsername = input("Username: ")

def username():
    if tUsername != rUsername:
        print("User not found.")
        blank = input("")
        exit()
username()

def password():
    if tPassword != rPassword:
        print("Incorrect password.")
        blank = input("")
        exit()
tPassword = input("Password: ")

password()

def typer():
    typerCMD = input("")

print ("Hello, and welcome to your new operating system. Type 'help' to get started.")
shell = input("--")
if shell == ("help"):
    print("Use the 'leave' command to shut down the system. Use the 'type' command to start a text editor.")
shell2 = input ("--")
if shell2 == ("leave"):
    print("Shutting down...")
    exit()
if shell2 == ("type"):
    typer()

But I want the program to run so that it will save the created username to a file so you don't have to create a new username every time you run it. Any tips? (And please don't judge me on my "text editor." That's just there so that there's a purpose to signing in.)

score 1 · Answer 1 · answered Feb 18 '16 at 04:55

You can create a dictionary of of username and corresponding password, and then save it to json file.

Suppose your dictinoary is of the type

user_dict = {rUsername : rPassword}

Save into the file "user.json" ie. Write operations

import json
with open("users.json", "w") as f:
    json.dumps(user_dict,f)

Read Operations

import json
with open("users.json", "r") as f:
     user_dict = json.loads(f)

danidee · Accepted Answer · 2016-02-18T05:18:20.513

You can write to a file like this

with open('myfile.txt', 'w') as f:
    f.write(rUsername)

a simple program that asks the user for their username and checks if it's in a file, if it's not present it writes their name to the file, thereby creating a new user, with this logic you should be on your way

while True:
    username = input('please enter your username or exit to quit the program')

    if username == 'exit':
        break
    else:

        with open('myfile.txt', 'r') as f:
            for line in f:
                print(line)
                if username == line:
                    print('you belong here')
                    break
            else:
                with open('myfile.txt', 'a') as f:
                    f.write(username)
                    print('You dont belong but your name has been saved')
                    break

score 0 · Answer 3 · edited May 23 '17 at 12:07

Following are function of Create User and check user present in system or not.

We are used Pickle library to store user details in dictionary structure.

Demo Code:

import os
import pickle
user_details_file = "user_details1.txt"

def createNewUser():
    """
        Create New USer.
        1. Accept USer name and PAssword from the User.
        2. Save USer Name and Password to File.
    """
    #- Check Login Detail file is present or not.
    if os.path.isfile(user_details_file):
        #- Load file into dictionary format.
        fp = open(user_details_file, "rb")
        data = pickle.load(fp)
        fp.close()
    else:
        #- Set empty dictionary when user details file is not found.
        data = {}

    while 1:
        username = raw_input("Enter Username:").strip()
        if username in data:
            print "User already exist in system. try again"
            continue

        password = raw_input("Enter password:")
        data[username] = password

        #- Save New user details in a file.   
        fp = open(user_details_file, "wb")
        pickle.dump(data, fp)
        fp.close()
        return True


def loginUSer():
    """
        Login User.
        1. Open  User Name and Password file.
        2. Accept User name and Password from the User.
        3. check User is present or not
    """    
    #- Check Login Detail file is present or not. 
    if os.path.isfile(user_details_file):
        fp = open(user_details_file, "rb")
        data = pickle.load(fp)
        fp.close()
    else:
        #- Load file into dictionary format.
        # We can return False from here also but why to tell user that your are first user of this application.
        data = {}

    username = raw_input("Enter Username:").strip()
    password = raw_input("Enter password:").strip()
    if username in data and password==data["username"]:
        print "You login"
        return True
    else:
        print "No user worong username or password"
        return False



if __name__=="__main__":
    new_userflag = raw_input("you want to create new user? yes/no").lower()
    if new_userflag=="yes":
        createNewUser()

    loginUSer()

Note:

raw_input() is used in Python 2.x
input in used in Python 3.x

Few links:

How can I save input to a file and then check the input from the file?

3 Answers3