About Python Interface

The Python interface is an application programming interface (API) for executing commands in Dymola Behavior Modeling using a Python program. It contains a number of functions for performing operations such as simulating, specifying variables, plotting, and exporting data.

Note: Before using the API, you need to install and configure a supported version of the Python programming language. Virtual Execution Interface officially supports the 32-bit version of Python 2.7 and Dymola Interface supports 32-bit and 64-bit versions of Python 2.7 and Python 3.5. For more information, see Installing Python Interface.

The Python package is included in the Dymola Behavior Modeling distribution. The package provides an API, based on an interface server that uses the HTTP protocol. The server runs in Dymola Behavior Modeling and receives function calls. The functions available through the Python interface are the functions available in the DymolaCommands library. For more information, see Launching HTTP Server.

Dymola Interface

The Dymola interface is used to interface Python and Dymola in 3DEXPERIENCE.

This API is globally compatible with Dymola and allows scripting a Dymola Behavior Modeling or stand-alone Dymola session.

Important: The Dymola Interface can only be used with an already running Dymola Behavior Modeling session. For starting a new Dymola Behavior Modeling session or multiprocessing, use the Virtual Execution Interface.

The main Python object in dymola.egg is the DymolaInterface. It can be invoked by the following API:

dymola = DymolaInterface(startDymola=False, port=44000)

The essential parameters for the API, among others, are startDymola and port. Following is the complete definition of DymolaInterface:

def __init__(self, dymolapath="", use64bit=True, port=-1, showwindow=False, debug=False, allowremote=False, nolibraryscripts=False, startDymola=True):


Parameters	Type	Description
`dymolapath`	String	This parameter represents the path to Dymola.exe. The default value, an empty string, indicates that the path is detected automatically.
`use64bit`	Boolean	This parameter represents the version of Dymola. The default value, `True`, indicates that the 64-bit version of Dymola is used. The value `False` indicates a 32-bit version.
`port`	Integer	This parameter represents the port number used for connecting to Dymola. The default value is `-1`, which indicates that the port is assigned automatically.
`showwindow`	Boolean	This parameter controls the visibility of the Dymola window when calling functions in the interface. The default value, `False`, indicates that the Dymola window is visible and runs in the background.
`debug`	Boolean	This parameter is used for debugging the Dymola Python interface. The default value is `False`. Setting the value to `True` sends the debug messages to the console.
`allowremote`	Boolean	This parameter when set to `True`, enables access from another machine. The default value is `False`, which indicates local connection.
`nolibraryscripts`	Boolean	This flag corresponds to the command-line argument with the same name. The default value is `False`.
`startDymola`	Boolean	This parameter enables starting of Dymola automatically. The default value is `True`.

For more information, see Dymola Interface Commands.

Virtual Execution Interface

Virtual Execution Interface can be used to start a new Dymola Behavior Modeling session. This allows running multiple Dymola Behavior Modeling sessions in parallel, executing python batch files and scripting using the Dymola Interface. It also allows efficient computation of Functional Mock-up Units (FMUs) by processing them in parallel.

You need to run the following command to start Python in a 3DEXPERIENCE runtime environment.

'3DEXPERIENCE directory'\win_b64\code\bin\CATSTART.exe -run "python.exe" -env Env -direnv "'3DEXPERIENCE directory'\CATEnv" -nowindow

Note: You must replace '3DEXPERIENCE directory' with your 3DEXPERIENCE installation directory.

For more information on commonly used services and functions, see Virtual Execution Interface Commands.

Note: Python or JavaScript result may be impacted by the content of an interactive session, as Dymola Behavior Modeling and stand-alone Dymola manage resources differently. For example, a 3D animation of the result in the Dymola javascript example does not work, and the plot result has a different interface.