UseState 0.2.0

Library for creating a dependency graph of cached properties

UseState

Wrap your class's instance methods with @use_state and @use_lazy_generated_state to create a dependency graph of cached properties that only regenerate when their dependencies change.

Uses Python's data descriptors to proxy (to the graph) access of properties. Graph nodes are stored on the instances of classes that use the decorators, for sane garbage collection sake.

Installing

Available on PyPI as UseState

$ pip install UseState

Examples

See examples folder

#!/usr/bin/env python3

import math

from UseState import use_state, use_lazy_generated_state

class Cylinder:
    def __init__(self, radius: float, height: float) -> None:
        self.radius = radius
        self.height = height

    @use_state()
    def radius(self) -> float:
        print("Calculating default radius")
        return 0.0

    @use_state()
    def height(self) -> float:
        print("Calculating default height")
        return 0.0

    @use_lazy_generated_state({"radius"})
    def area(self) -> float:
        print("Calculating area")
        return self.radius * self.radius * math.pi

    @use_lazy_generated_state({"area", "height"})
    def volume(self) -> float:
        print("Calculating volume")
        return self.area * self.height

def main() -> None:
    c = Cylinder(4.0, 8.0)

    print(c.area)
    # Calculating area
    # 50.26548245743669

    print(c.volume)
    # Calculating volume
    # 402.1238596594935

    c.radius = 4.0 # doesn't cause invalidation because value is same

    print(c.volume)
    # 402.1238596594935

    c.radius = 1.0 # invalidates area, which invalidates volume

    print(c.volume)
    # Calculating area
    # Calculating volume
    # 25.132741228718345

    print(c.area) # cached by previous call to volume
    # 3.141592653589793

    print(c.volume)
    # 25.132741228718345

if __name__ == "__main__":
    main()