从文本文件检查字典键值

Question

Python beginner here and I'm trying to create a login system (using Python 3). I've created a function to store user's username and password as a dictionary {uname:pswd} in a text file. I created another function that lets the user log in but I don't know how to check if their details match the dictionary keys and its corresponding values in the text file.

This is what I've done so far:

def user_login(): #login function
    uname=input("Enter username:")
    pswd=input("Enter password:")
    d={uname:pswd}
    loginfile=open('logindata.txt', 'r')
    with loginfile as f:
        for line in f:
            if d.get(uname)==pswd: #should check user input matches dictionary in text file
                return "Accepted"
            else:
                return "Wrong username/password"
    loginfile.close()

With this, I get an error message: AttributeError: 'str' object has no attribute 'get' . It reads it as a string, so how do I get the code to read it as a dictionary? Also, as a newbie, I'm pretty sure some parts of my code could be wrong. Any suggestions on what I should fix?

Answer 1

I execute your same code and got no error, but no matter what you typed as credentials, they always were accepted. Here is a way to solve your problem

def user_login():  # login function
    uname = input("Enter username:")
    pswd = input("Enter password:")
    d = {uname: pswd}

    with open('logindata.txt', 'r') as f: # here I open logindata.txt in read mode and I call it f
        credentials = f.read().split('\n') # I make a list with the credentials by splitting the lines of the file (I think your file has 2 lines: username and password)
        check_dict = {credentials[0]: credentials[1]} # I create the dictionary with the credentials

    if d.get(uname) == check_dict.get(credentials[0]):  # check if the input username and password (d dictionary) are the same as those stored in the logindata.txt file
        return "Accepted"
    else:
        return "Wrong username/password"

the problem is that your code checks if the value of uname in the d dictionary is equal to pswd , but when you declared the dictionary d={uname:pswd} you are assigning the value of pswd to uname , so they will always be the same. I also used with open('logindata.txt', 'r') as f: instead of loginfile=open('logindata.txt', 'r') with loginfile as f: ... loginfile.close() because is just a better way to open a file and you have to type less code. Anyway I would suggest not using dictionaries and simply doing this

def user_login():  # login function
    uname = input("Enter username:")
    pswd = input("Enter password:")

    with open('logindata.txt', 'r') as f: # here I open logindata.txt in read mode and I call it f
        credentials = f.read().split('\n') # I make a list with the credentials by splitting the lines of the file (I think your file has 2 lines: username and password)

    if uname == credentials[0] and pswd == credentials[1]: # check if input credentials are the same as stored credentials
        return "Accepted"
    else:
        return "Wrong username/password"

If none of these codes works I suggest to include the function that stores the credentials in logindata.txt . If you need help to be able to have multiple accounts to log in you should definitely add that function. Hope this solved your problem