[Python] How is it possible to use colon to declare an variable?!

Martin156131

so i watched the Python crash course video for Blender recommend from here https://wiki.osarch.org/index.php?title=Start_coding
And in the video (43 min) he uses colon between noice_scale and FloatProperty

How is that possible in python syntax?

theoryshaw

not an expert, but i think...
https://docs.python.org/3/glossary.html#term-variable-annotation

cvillagrasa

Prior to Blender 2.8, props were assigned with the equal sign, and now are indeed treated as annotations:
https://wiki.blender.org/wiki/Reference/Release_Notes/2.80/Python_API/Addons#Class_Property_Registration

Gorgious

This is indeed a python annotation.
In the context of Blender's python API it is used to dynamically populate the operator instances that are crated at runtime when you click on an operator's button. You can then access these properties as standard members of the operator instance.

In order for the API to recognize them you have to declare them as annotations. Otherwise they're just plan old python attributes of the main operator class (except the few attributes beginning with bl_).