Welcome to Atom

Atom is a framework for creating memory efficient Python objects with enhanced features such as dynamic initialization, validation, and change notification for object attributes. It provides the default model binding behavior for the Enaml UI framework.

Examples:

from atom.api import Atom, Str, Range, Bool, observe


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

    """
    last_name = Str()

    first_name = Str()

    age = Range(low=0)

    debug = Bool(False)

    @observe('age')
    def debug_print(self, change):
        """ Prints out a debug message whenever the person's age changes.

        """
        if self.debug:
            templ = "{first} {last} is {age} years old."
            s = templ.format(
                first=self.first_name, last=self.last_name, age=self.age,
            )
            print(s)

    def _default_first_name(self):
        return 'John'


john = Person(last_name='Doe', age=42)
john.debug = True
john.age = 43  # prints message
john.age = 'forty three'   # raises TypeError

Starting with atom 0.8.0 atom object can also be defined using type annotations.

from atom.api import Atom, observe

class InventoryItem(Atom):
    """Class for keeping track of an item in inventory."""

    name: str
    unit_price: float
    quantity_on_hand: int = 0

    def total_cost(self) -> float:
        return self.unit_price * self.quantity_on_hand

    @observe("unit_price")
    def check_for_price_reduction(self, change):
        savings = change.get("oldvalue", 0) - change.get("value")
        if savings > 0:
            print(f"Save ${savings} now on {self.name}s!")

>>> w = InventoryItem(name="widget", unit_price=1.99, quantity_on_hand=10)
>>> w.unit_price = 1.00
Save $0.99 now on widgets!