I finally resolved my issue !
It seems Dreamfactory only supports Python 2 and I had 3.6 version
I launched the service.math python script directly in cmd and I got the error “ImportError: No module named httplib”
This error means I am running Python 2 code on Python 3. In Python 3, the module has been renamed to http.client.
Then I removed Python 3.6 and added python 2.7, updated the .env file, launched artisan commands and tested my python script and… I got a new error !
It appeats the script given (in http://wiki.dreamfactory.com/DreamFactory/Features/Scripting/Python and http://wiki.dreamfactory.com/DreamFactory/Tutorials/Python_Custom_scripting_service_math) uses em-dash in a comment.
But when you save the script, the em-dash is saved as an encoded character and everybody know Python 2.7 has encoding issues (sorry I can not display a second picture)…
So I resolved my problem but please, if someone can update links given above and tell users they need python 2 and remove the em-dash in examples !