Changing stored scores with certain username in a txt file. Python

I just started my gcse computer science course where we learn python. I need help with updating a user’s score to a certain account. I am storing usernames passwords and scores in a text file and need to know how to change a score from a certain account. My text file is set out like this:

Bobby,pass,98
Pip,Noob,19
pog,man,1234

E.g Bobby is the username and pass is the password and 98 is the score so what I need is a way to scan for that certain username and change the score (98).
The code that I use for creating an account and logging in is this:

def SignUp():
    print("""Please enter a username and password.""")
    newUsername = input("Your username: ")
    #Now askes for a password
    print("""Cool now enter a password
    """)
    
    newPassword = input("Your Password: ")
    print("Nice.")
    newscore = input("Now give me a score")
    #Puts the username and password into a txt
    file = open("Login.txt","a")
    file.write("""
""")
    file.write (newUsername)
    file.write (",")
    file.write (newPassword)
    file.write (",")
    file.write (newscore)
    file.close()
    
    
def Login():
    userLogin = input("Please enter your username. ")
    userPass = input("Password: ")
    
    logged_in = False
    with open('Login.txt', 'r') as file:
        for line in file:
            username, password, score = line.split(',')
            if username == userLogin:
            # Check the username against the one supplied
                logged_in = password == userPass
                print(str(score))
                print("you logged in")
                break



SignUp()
Login()

I’m quite new to python as you can probably tell so any help will be appreciated.

>Solution :

The easiest way is to read the entire file, then rewrite the entire thing with the changed number. This is only practical with small files:

def changeScore(username, newScore):
    file = open("Login.txt", "r")
    lines = file.readlines()
    file.close()

    file = open("Login.txt", "w")
    for line in lines:
        data = line.split(",")
        if data[0] == username:
            data[2] = str(newScore) + "\n"
            file.write(",".join(data))
        else:
            file.write(line)
    file.close()