import json

class Person:
    def __init__(self):
        self.name = input('Enter your name: ')
        self.age = int(input('Enter your age: '))
        self.sex = input('Enter your sex: ')
        self.phone_number = input('Enter your phone number: ')
        self.address = input('Enter your address: ')

    def toJSON(self):
        return json.dumps(self, default=lambda o: o.__dict__,
                          sort_keys=True, indent=4)

while True:
    person = Person()

    with open('person_info.txt', 'a') as file:
        file.write(person.toJSON() + ",")
        print("Contact is added!")