Changes to Python interpreter loading behaviour in FME 2019+

Liz Sanderson
Liz Sanderson
  • Updated

FME Version

  • FME 2020.0
Affects 2019.0+
Resolved 2022.0


Why is FME ignoring the Python Compatibility parameter and loading a different Python interpreter for my workspace?

The Python Compatibility parameter of a workspace allows users to select which Python interpreter is used by FME when running a workspace . In FME 2019.0+, users may notice FME ignoring this parameter and loading a different Python interpreter when running a workspace. 

In order to promote the use of Python 3.x in FME due to the deprecation of Python 2.7, the Python loading behaviour was changed in FME 2019.0+ to use Python 3.7+ when the workspace does not contain user-defined Python. User-defined Python includes Python scripted parameters, startup scripts, shutdown scripts, PythonCreator, or PythonCaller.

Users will see the following message in the translation log if the workspace uses Python but does not contain any user-defined Python.

The workspace does not contain user Python. FME will attempt to use a Python 3.7+ interpreter

For FME 2019.x and higher, if you have no user-defined Python in your workspace but wish to use a specific interpreter, please add a small startup Python script.

To do this, go to Navigator > Workspace Parameters > Scripting > Startup Python and add the following line:


Note: If a workspace’s Python Compatibility is set to Esri ArcGIS 2.7, Esri ArcGIS 3.5, or Esri ArcGIS 3.6+, FME will verify the respective Esri products are installed and licensed when the translation starts. This license check will still occur even if FME does not load Esri’s Python interpreter.

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