Password and Username Verification

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Hello, I have been doing my coursework for computer science and my teacher advised that we go home and practice python in between hours in the coursework, I need help on Password and Username Verification as it requires the password and username to be stored in a .txt file outside of the program. I do not know how to check the .txt file against the logon information. This also must be able to work with more than one username and password. Thanks

I don't know if this violates the homework terms, if so please let me know.

Name = input("What is your first Name?\n")
while True:
    try:
        Age = int(input("What is your age?\n"))
        Year = int(input("What is your year group?\n"))
        break
    except ValueError:
        print ("Error, Try again")
NameFirst = Name[0]
NameMain = Name[1:3]
Name = NameFirst.upper()+NameMain.lower()
#print (Name)
Username = (Name + str(Age))
#print (Username)
print ("This is your username for the quiz",Username)
while True:
    Password = input("Please Enter a Password\n")
    PasswordCheck = input("Please Re Enter the password\n")
    if Password.lower() == PasswordCheck.lower():
        break
    else:
        print ("Passwords Do Not Match!\nPlease Re Try.")
f = open( 'Users.TXT', 'a' )
f.write(Username + '\n' + Password + '\n')
f.close()

#Logon
file = open('Users.TXT', 'r')
Data = file.read()
file.close()
#print (Data)
while true
LogonUsername = input("Please Enter Your Username\n")