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https://github.com/lethain/systems

systems is a set of tools for describing, running and visualizing systems diagrams.
https://github.com/lethain/systems

system-modeling systems-dynamics systems-thinking

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systems is a set of tools for describing, running and visualizing systems diagrams.

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README 

        

# Systems



`systems` is a set of tools for describing, running and visualizing

[systems diagrams](https://lethain.com/systems-thinking/).



Installation directions are below, and then get started by [working through the tutorial](./docs/tutorial.md)

or reading through the [Jupyter notebook example](./notebooks/hiring.ipynb) example.



For a more in-depth look at the system syntax, please read [the syntax specification](./docs/spec.md).



## Quickest start



Follow the installation instructions below, then write a system definition

such as:



    Start(10)

    Start  > Middle @ 2

    Middle > End



You can then evaluate your system (use `--csv` for an importable format):



    cat tmp.txt | systems-run -r 3



            Start   Middle  End

    0       10      0       0

    1       8       2       0

    2       6       3       1

    3       4       4       2



See [the tutorial](./docs/tutorial.md) for more detailed starting information.



## Installation



To install via PyPi:



    pip install systems



To install for local development:



    git clone https://github.com/lethain/systems.git

    cd systems

    python3 -m venv ./env

    source ./env/bin/activate

    python setup.py develop



Run tests via:



    python3 -m unittest tests/test_*.py



Or run a single test via:



    python3 tests/test_parse.py TestParse.test_parse_complex_formula



Please open an Github issue if you run into any problems!



## Jupyter notebooks



Likely the easiest way to iterate on a model is within a Jupyter notebook.

See an [example notebook here](./notebooks/hiring.ipynb).

To install, follow the installation steps above, and followed by:



    # install graphviz

    brew install graphviz



    # install these additional python packages

    pip install jupyter pandas matplotlib



## Using the command line tools



There are four command line tools that you'll use when creating and debugging

systems/



`systems-run` is used to run models:



    $ cat examples/hiring.txt | systems-run -r 3

    PhoneScreens    Onsites Offers  Hires   Employees       Departures

    0       0               0       0       0       5               0

    1       25              0       0       0       5               0

    2       25              12      0       0       5               0

    3       25              12      6       0       5               0



`systems-viz` is used to visualize models into [Graphviz](https://www.graphviz.org/):



    $ cat examples/hiring.txt | systems-viz

    // Parsed

    digraph {

      rankdir=LR

      0 [label=Candidates]

      1 [label=PhoneScreens]

      // etc, etc, some other stuff

    }



Typically you'll pipe the output of `systems-viz` into `dot`, for example



    $ cat examples/hiring.txt | systems-viz | dot -Tpng -o tmp.png



`systems-format` reads in a model, tokenizes it and formats the tokens

into properly formatted results. This is similar to `gofmt`, and could

be used for ensuring a consistent house formatting style for your diagrams.

(It was primarily implemented to support generating human readable error

messages instead of surfacing the tokens to humans when errors arise.)



    $ cat examples/hiring.txt | systems-fmt

    [Candidates] > PhoneScreens @ 25

    PhoneScreens > Onsites @ 0.5

    # etc etc



`systems-lex` generates the tokens for a given system file.

This is typically most useful when you're extending the lexer

to support new types of functionality, but can also be useful

for other kinds of debugging:



    $ cat examples/hiring.txt | systems-lex

    ('lines',

       [('line',

         1,

         [('comment', '# wrap with [] to indicate an infinite stock that')]),

        ('line', 2, [('comment', "# isn't included in each table")]),

	('line', 3, [('comment', '# integers are implicitly steady rates')]),

	('line',

	 4,

         [('infinite_stock', 'Candidates', ('params', [])),

	  ('flow_direction', '>'),

          ('stock', 'PhoneScreens', ('params', ())),

          ('flow_delimiter', '@'),

          ('flow', '', ('params', (('formula', [('whole', '25')]),)))]),

	...

      ]

    )



## Error messages



The parser will do its best to give you a useful error message.

For example, if you're missing delimiters:



    cat examples/no_delim.txt | systems-run

    line 1 is missing delimiter '>': "[a] < b @ 25"



At worst, it will give you the line number and line that is

creating an issue:



    cat examples/invalid_flow.txt | systems-run

    line 1 could not be parsed: "a > b @ 0..2"



## Uploading distribution



If you are trying to install this on PyPi, the steps are roughly:



    python3 -m pip install --user --upgrade pip

    python3 -m pip install --user --upgrade wheel

    python3 -m pip install --user --upgrade twine

    python3 setup.py sdist bdist_wheel

    twine upload --repository-url https://upload.pypi.org/legacy/ dist/*



That should more or less work. :)