jNeqSim

Python interface for the NeqSim java package, with stubs. Java interface is created with jpype, and stubs are generated with stubgenj

PYPI

https://pypi.org/project/jneqsim/

[!NOTE] JNeqSim mirrors NeqSims versions

Demo

Example

from jneqsim import neqsim


def pressurize_gas():
    inlet_fluid = neqsim.thermo.system.SystemSrkEos()
    neqsim.thermo.system.SystemSrkEos()
    thermo_ops = neqsim.thermodynamicOperations.ThermodynamicOperations(inlet_fluid)
    inlet_fluid.addComponent("methane", 100.0)

    inlet_fluid.setTemperature(10, "C")
    inlet_fluid.setPressure(20, "bara")
    inlet_fluid.setMultiPhaseCheck(True)
    inlet_fluid.setSolidPhaseCheck("methane")

    thermo_ops.TPflash()
    thermo_ops.bubblePointTemperatureFlash()

    inlet_fluid.initProperties()
    enthalpy = inlet_fluid.getEnthalpy()

    inlet_fluid.setPressure(1.0, "bara")
    thermo_ops.PHflash(enthalpy)

Dependencies

jpype

Version Management

jneqsim uses a controlled release process to ensure compatibility:

Pinned Versions: Each jneqsim release is pinned to a specific, tested NeqSim JAR version
Automated Updates: The nightly CI workflow automatically checks for new NeqSim releases and publishes updated jneqsim packages when available
No Auto-Updates: Applications using jneqsim will not automatically download newer NeqSim versions - they use the tested version that comes with their installed jneqsim package
Cache Management: Downloaded JARs are cached locally in ~/.jneqsim/cache for faster subsequent usage

Development

Running Tests

The project uses pytest with custom markers to categorize tests. Test dependencies are already included in the development dependencies.

# Install development dependencies (includes pytest and pytest-mock)
poetry install

# Run unit tests (fast, excludes tests marked as slow)
pytest -v -m "not slow" tests/

# Run all tests (may download JARs for integration tests)
pytest -v tests/

# Run with coverage (requires pytest-cov)
poetry add --group dev pytest-cov
poetry run pytest --cov=jneqsim --cov-report=html tests/

Test markers:

slow: Tests that may download files or take longer to run
integration: Integration tests that require external dependencies
unit: Fast unit tests (default)

:+1: Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

Release files for jneqsim 3.18.0

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for jneqsim 3.18.0
File	Size	Uploaded
jneqsim-3.18.0.tar.gz	2.9 MB	Aug 19, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for jneqsim 3.18.0
File	Interpreter	ABI	Platform	Reset
jneqsim-3.18.0-py3-none-any.whl 928.6 kB Aug 19, 2026	Python 3	none	any	Details

Total release size: 3.8 MB

Release files / jneqsim-3.18.0.tar.gz

Download URL	jneqsim-3.18.0.tar.gz
Size	2.9 MB
Tags	Source
SHA-256 checksum How to use checksums	`a50a8dfce38ad7ed9ca5950afa7a6c10f69a98c83bb4c65875ae6a7a0e93c1ed`
BLAKE2b-256 checksum How to use checksums	`5292d8fe11fb7de17d15c0fed8ea2b43ac88ddde7ea929736abe7e7b6f9f3a61`
Upload date	Aug 19, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	Yes
Uploaded via	`twine/7.0.0 CPython/3.13.14`

Release files / jneqsim-3.18.0-py3-none-any.whl

Download URL	jneqsim-3.18.0-py3-none-any.whl
Size	928.6 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`aed5c710777cf0b83369317ddf606cb130238a0a078456af2054cfe8b8736e09`
BLAKE2b-256 checksum How to use checksums	`a87b0f0792af5e9bffa2c2823a9a809b3874aaebb55d41d864c88f7ee743b3f2`
Upload date	Aug 19, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	Yes
Uploaded via	`twine/7.0.0 CPython/3.13.14`