Default Value Example

Demonstrate all the ways to initialize a value

  1. Pass the value directly

  2. Assign the default value explicitly

  3. Provide the value during initialization of the object

  4. Provide factory callable that returns a value

  5. Use a _default_* static method

Tip

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

$ python default_value.py

Example Atom Code

#------------------------------------------------------------------------------
# Copyright (c) 2013-2017, Nucleic Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file LICENSE, distributed with this software.
#------------------------------------------------------------------------------
""" Demonstrate all the ways to initialize a value

1. Pass the value directly
2. Assign the default value explicitly
3. Provide the value during initialization of the object
4. Provide factory callable that returns a value
5. Use a _default_* static method

"""
from __future__ import (division, unicode_literals, print_function,
                        absolute_import)

import sys

from atom.api import Atom, Str, Int


def get_mother():
    return 'Maude ' + get_last_name()


def get_last_name():
    """ Return a last name based on the system byteorder.

    """
    return sys.byteorder.capitalize()


class Person(Atom):
    """ A simple class representing a person object.

    """
    first_name = Str('Bob')

    age = Int(default=40)

    address = Str()

    mother = Str(factory=get_mother)

    last_name = Str()

    def _default_last_name(self):
        return get_last_name()


if __name__ == '__main__':
    bob = Person(address='101 Main')
    print((bob.first_name, bob.last_name, bob.age))
    print(bob.mother)