A simple lazy Python Calculation Engine.

The module is still in development. You can install it by cloning this repository and using the poetry install command.

git clone git@github.com:bsdz/calcengine.git cd calcengine python3 -mvenv --prompt calceng .venv . ./.venv/bin/activate poetry install

Alternatively, you can add to your existing poetry project:

poetry add git+https://github.com/bsdz/calcengine.git

Or install via pip:

pip install git+https://github.com/bsdz/calcengine.git#master

The core module for the calculation engine only uses core python standard library.

The demo spreadsheet application uses pyqt5, pandas, matplotlib and pillow.

First instantiate a CalcEngine and use watch decorator to register functions as nodes. Note that a function along with any arguments and keyword arguments make a unique node.

from calcengine import CalcEngine ce = CalcEngine() @ce.watch() def a(): print("..in a") return 100 @ce.watch() def b(): print("..in b") return a() @ce.watch() def c(x, y): print(f"..in c with x={x} and y={y}") return 2 * a() + x * y @ce.watch() def d(x, y=0): print(f"..in d with x={x} and y={y}") return 3 * b() + x - y @ce.watch() def e(): print("..in e") _x = d(5, y=-3) return c(2, 3) - 5 + _x @ce.watch() def f(): print("..in f") return d(0) + e()

Calling a function will cache all values and path during first run.

>>> f() ..in f ..in d with x=0 and y=0 ..in b ..in a ..in e ..in d with x=5 and y=-3 ..in c with x=2 and y=3 809

And obviously a 2nd invocation will retrieve the final value from cache.

>>> f() 809

Invalidating a node by calling function helper method.

>>> e.invalidate() >>> f() ..in f ..in e 809

Invalidating a node without arguments if previous call did have arguments won't have any effect.

>>> d.invalidate() >>> f() 809

Whereas with arguments specified exactly as prior call will. Note the sensitivity of argument specification.

>>> d.invalidate(5, y=-3) >>> f() ..in f ..in e ..in d with x=5 and y=-3 809

It is also possible to add a trigger that will be called on completion of a function. This might be used to produce some form of data binding in applications.

def my_trigger(res): print(f"got {res}") >>> c.node_calculated.append(my_trigger) >>> c.invalidate(2, 3) >>> f() call f call e call c with x=2 and y=3 got 206 809

Included is a simple spreadsheet demo. Read more here

To install the dependencies required by the demo. When cloning this repo also include the "demo" extras.

poetry install -E demo python demo/spreadsheet/main.py

• Support watching global variables.
• Support multiprocessing.
• Support asyncio?.

Some similar packages spotted. None of them tested.

• pyungo
• dask
• schedula
• graphkit
• mdf