I want to use FreeCAD with external python apps with my own graphical interface

[damas2019]

Hi everyone,
I'm a rookie in FreeCad and Python. I also heard about Pyside 2 and I want to build my own app as first layer view to user.
Exemple:
First of all, I have a design in FreeCad and then I want my application user to send their own dimension to generate the G-CODE at the end.
These are the steps:
1. I want my app to get the dimensions input interface: Height, withd, ...
2. Validate the new dimension with embedded view of the shapes
3. Click on the botton in my app to send to Freecad to generate the G-CODE

Question: Do you have some sample code for this king of external GUI interface or do you have a way to advice me for python scripts.

Thanks

[Kunda1]

We need to make a wiki page for this topic as it is growing in popularity.
Check out: https://pythoncvc.net/?p=869