I have created a function to save contents of a created objects of id's to a different files based on what kind of objects they are, however I can't seem to fix it. Here is my code:

def write_to_file(
    file_name: str,
    list_name: list,
):
    """This function is to write id's to file.

    It creates file with given file_name parameter and it loops through the list
    that we pass from another function.
    """
    try:
        id_to_write = ""
        if file_name == "dummy_test1_datas.txt":
            id_to_write == "test_1_id"
        elif file_name == "dummy_test2_datas.txt":
            id_to_write == "test_2_id"
        elif file_name == "dummy_test3_datas.txt":
            id_to_write == "test_3_id"
        print(id_to_write)
        with open(file_name, "w", encoding="utf-8", newline="") as f:
            for data in list_name:
                f.writelines(
                    data.user_id if file_name == "dummy_user_datas.txt" else data
                )
        print(f"Alle toegevoegde id's zijn opgeslagen in {file_name} bestand.")
    except:
        print("Probleem bij het schrijven naar een bestand.")

The issue that I am having is that I can't make it sure that, if my parameter of file_name equals "user.txt" then f.writelines (should be data.user_id), if file_name is something else then it should be data.something_id for example.

Expectation: based on file_name it should conditionally change to data.user_id or data.test_id e.t.c.

Currently it does not save any id to file, since i have this:

data.user_id if file_name == "dummy_user_datas.txt" else data

What do i need to change in the code above so this conditionally changes to user_id or test1_id or test2_id e.t.c. in order to save id's?