Modello

This project aims to explore symbolic modeling with object orientated programming. The heavy lifting is done by the sympy library. This module just provides a class to derive models from.

An example based on examples/geometry.py:

from modello import InstanceDummy, Modello
from sympy import sqrt


class RightAngleTriangle(Modello):
    a = InstanceDummy("a", real=True, positive=True)
    b = InstanceDummy("b", real=True, positive=True)
    c = sqrt(a**2 + b**2)


T = RightAngleTriangle("T", a=3, b=4)
assert T.c == 5
T = RightAngleTriangle("T", b=4, c=5)
assert T.a == 3

The best place to see how this can be used is to look in the examples directory, which still needs padding out.

The functionality is covered by tests in both test_modello.py and doctests+tests in the examples.

Installation

This can be installed using one of:

# using pipenv
pipenv install modello

# using pip
pip install --user modello

# using git+pipenv
pipenv install git+https://github.com/Code0x58/modello.git#egg=modello

# using git+pip
pip install --user git+https://github.com/Code0x58/modello.git#egg=modello

Currently this requires Python 3.6+ but the version requirements can drop a couple of minor versions easily if there is interest. Python 2.7 isn't planned to be supported as the Modello class relies on PEP-3115.

Development

Run the tests and linting with python setup.py test. Pushes have the test suite run against them, and will also publish a release if tagged thanks to GitHub Actions. You can reproduce the Actions locally using act, e.g. TWINE_USERNAME= TWINE_PASSWORD= act.

You can run all the tests with python setup.py test. If you want to run a subset of tests or otherwise pass arguments to pytest, use ./pytest … e.g.:

./pytest examples/jobs.py::jobs.Job

TODO:

• elaborate on tests/examples
• think about extending the functionality to allow for a more complete system of constraints, use the RightAngleTriangle example as a base
• work out patterns for labels/names on symbols so they render nicely
• for mypy, consider getting value from or removing it
• implement a first attempt at nested models (named, rather than lists, which would be nice)
• think about the possibility of symbolic (instance) dummies to allow live updates to system rather than modello instantiation being final
• think about defaults (e.g expenses=0)