Skip to main content

A lightweight framework that enables the packaging of Python3.x code as co-simulation FMUs.

Project description


A lightweight framework that enables the packaging of Python3.x code as co-simulation FMUs.

License: MIT contributions welcome CI PyPI


How do I build an FMU from python code?

  1. Install pythonfmu package:
pip install git+
  1. Create a new class extending the Fmi2Slave class declared in the pythonfmu.fmi2slave module.
  2. Run pythonfmu-builder to create the fmu.
usage: pythonfmu-builder [-h] -f SCRIPT_FILE [-d DEST]
                         [--doc DOCUMENTATION_FOLDER]
                         [Project files [Project files ...]]

Build a FMU from a Python script.

positional arguments:
  Project files         Additional project files required by the Python

optional arguments:
  -h, --help            show this help message and exit
                        Path to the Python script.
  -d DEST, --dest DEST  Where to save the FMU.
                        Documentation folder to include in the FMU.
Write the script
from pythonfmu import Fmi2Causality, Fmi2Slave, Boolean, Integer, Real, String

slave_class = "PythonSlave"  # REQUIRED - Name of the class extending Fmi2Slave

class PythonSlave(Fmi2Slave):

    author = "John Doe"
    description = "A simple description"

    def __init__(self, instance_name):

        self.intOut = 1
        self.realOut = 3.0
        self.booleanVariable = True
        self.stringVariable = "Hello World!"
        self.register_variable(Integer("intOut", causality=Fmi2Causality.output))
        self.register_variable(Real("realOut", causality=Fmi2Causality.output))
        self.register_variable(Boolean("booleanVariable", causality=Fmi2Causality.local))
        self.register_variable(String("stringVariable", causality=Fmi2Causality.local))

    def do_step(self, current_time, step_size):
        return True
Create the FMU
pythonfmu-builder -f pythonfmu

In this example a python class named PythonSlave that extends Fmi2Slave is declared in a file named pythonfmu is a optional folder containing additional project files required by the python script. Project folders such as this will be recursively copied into the FMU. Multiple project files/folders may be added.


PythonFMU does not bundle Python, which makes it a tool coupling solution. This means that you can not expect the generated FMU to work on a different system (The system would need a compatible Python version and libraries). But to ease its usage the wrapper is compile using the limited Python API. So the provided binary libraries for Linux and Windows 64-bits should be compatible with any Python 3 environment. If you need to compile the wrapper for on a specific configuration, you will need cmake and a C++ compiler. The commands for building the wrapper on Linux and on Windows can be seen in the GitHub workflow.

PythonFMU does not automatically resolve 3rd party dependencies either. If your code includes e.g. numpy, the target system also needs to have numpy installed.

Would you rather build FMUs in Java? Check out FMI4j!
Need to distribute your FMUs? FMU-proxy to the rescue!


This works has been possible thanks to the contributions of @markaren from NTNU-IHB and @fcollonval from Safran SA.

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Files for pythonfmu, version 0.3.0
Filename, size File type Python version Upload date Hashes
Filename, size pythonfmu-0.3.0-py3-none-any.whl (214.7 kB) File type Wheel Python version py3 Upload date Hashes View hashes
Filename, size pythonfmu-0.3.0.tar.gz (199.1 kB) File type Source Python version None Upload date Hashes View hashes

Supported by

Elastic Elastic Search Pingdom Pingdom Monitoring Google Google BigQuery Sentry Sentry Error logging AWS AWS Cloud computing DataDog DataDog Monitoring Fastly Fastly CDN DigiCert DigiCert EV certificate StatusPage StatusPage Status page