Checks objects that were in list when it was stated but doesn't check objects appended to the list by user

When I try to check if the user’s input is the same as an object attribute in a list it checks the objects that were stated within the list instead of objects that were appended to the list.

This was a problem that was really hard to explain and I tried my best to. Please let me know if it doesn’t make sense or if you want more information.

I am making a contact list for context. I made a contact class with a name, number, and address attributes. I am trying to see if a number that the user inputs is the same an object’s number attribute in a list. However when I was debugging and putting contacts in the list when it is stated, it works. When I append new contacts and try to see if the code knows if the user’s input is the same as the appended contacts it doesn’t work.

Here is my code:

class Contact:
    def __init__(self, name, number, address):
        self.name = name
        self.number = number
        self.address = address

    def __str__(self):
        return f"{self.name}, ({self.number}), {self.address}"


contact_list = []


def add_contact():
    global contact_list
    valid_name = False
    valid_number = False
    while not valid_name:
        contact_name = input("Who would you like to add as your contact?: ")
        name_taken = False
        for contact in contact_list:
            if contact.name == contact_name:
                print("Name is taken in contacts!")
                name_taken = True
                break
        if not name_taken:
            valid_name = True
    while not valid_number:
        contact_number = input("What is their number?: ")
        if len(contact_number) == 10 and contact_number.isnumeric():
            number_taken = False
            for contact in contact_list:
                if contact.number == int(contact_number):
                    print("Number is taken in contacts!")
                    number_taken = True
                    break
            if not number_taken:
                valid_number = True
            else:
                valid_number = False
        else:
            print("Invalid number!")
    contact_address = input("What is their house address?: ")
    new_contact = Contact(contact_name, contact_number, contact_address)
    contact_list.append(new_contact)
    print("Contact list:")
    for contact in contact_list:
        print("- " + contact.__str__())


add_contact()
add_contact()