# Hello World Example

Hello world example: how to write an atom class.

Tip

To see this example in action, download it from `hello_world` and run:

    $ python hello_world.py

## Example Atom Code

    # --------------------------------------------------------------------------------------
    # Copyright (c) 2013-2025, Nucleic Development Team.
    #
    # Distributed under the terms of the Modified BSD License.
    #
    # The full license is in the file LICENSE, distributed with this software.
    # --------------------------------------------------------------------------------------
    """Hello world example: how to write an atom class."""

    from atom.api import Atom, Str

    class Hello(Atom):
        message = Str("Hello")

    if __name__ == "__main__":
        hello = Hello()
        print(hello.message)
        hello.message = "Goodbye"
        print(hello.message)