Skip to main content

Define real, inheritable, and efficient Python classes using variable annotations

Project description

typedobject

Define real, inheritable, and efficient Python classes using TypedDict-like syntax.

Getting started

Install from pip.

python -m pip install typedobject

Then, annotate your class with typedobject and declare its member fields using variable annotations.

from typedobject import typedobject

@typedobject
class Point:
    x: int
    y: int

Then construct the object using either positional or keyword arguments.

pt1 = Point(10, 20)
pt2 = Point(x=10, y=20)
assert pt1 == pt2

You can define methods, including __init__.

@typedobject
class Rectangle:
    pt1: Point
    pt2: Point

    def __init__(self, x1, y1, x2, y2):
        self.pt1 = Point(x1, y1)
        self.pt2 = Point(x2, y2)

    def area(self):
        return (self.pt2.x - self.pt1.x) * (self.pt2.y - self.pt1.y)

rect = Rectangle(1, 1, 3, 3)
assert rect.area() == 4

Unlike TypedDict, the defined classes are actually fresh new classes, not dicts.

assert isinstance(rect, Rectangle)
assert not isinstance(rect, Point)

Inheritance works just fine.

@typedobject
class RoundedRect(Rectangle):
    corner_radius: int

rr = RoundedRect(Point(1, 1), Point(3, 3), 1)

Note that the derived class overrides __init__, unless you use .no_init.

@typedobject.no_init
class RoundedRect2(Rectangle):
    corner_radius: int

rr = RoundedRect2(1, 1, 3, 3)
assert not hasattr(rr, 'corner_radius')

Typed object classes, unlike dataclass, specify __slots__, which makes access to attributes faster and makes objects take less memory, but prevents adding new fields dynamically.

They also prevent multiple inheritance.

# raises TypeError
class RectangleWithAPoint(Rectangle, Point):
    pass

You can, however, inject mixins.

class TwoDObjectMixin:
    def area(self):
        return self.width() * self.height()

@typedobject
class Rectangle2(TwoDObjectMixin):
    pt1: Point
    pt2: Point

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

typedobject-1.1.1.tar.gz (7.9 kB view hashes)

Uploaded Source

Built Distribution

typedobject-1.1.1-py3-none-any.whl (6.9 kB view hashes)

Uploaded Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page