Python - Funciona la primera vez

import json

filename = 'username.json'

try:

    with open(filename) as f_obj:

        username = json.load(f_obj)

except FileNotFoundError:

    username = input("What is your name? ")

    with open(filename, 'w') as f_obj:

        print("We'll remeber you when you come back, " + username + "!!")

else:

    print("Welcome back, " + username + "!")

import json

filename = "username.json"

try:

    with open(filename) as f_obj:

        username = json.loads(f_obj.read())

except FileNotFoundError:

    username = input("What is your name? ")

    with open(filename, "w") as f_obj:

        user = {"username": username}

        json.dump(user, f_obj)

        print("We'll remeber you when you come back, " + username + "!!")

else:

    print("Welcome back, " + username["username"] + "!")