Modules duplication

[Durman]

Problem statement

Because of this code

sverchok/core/__init__.py

Lines 96 to 99 in a5d0742

	print('sv: import settings')
	import_settings(imported_modules, sv_name)
	print('sv: import all modules')
	import_all_modules(imported_modules, mods_bases)

sverchok/__init__.py

Lines 64 to 66 in a5d0742

	# make sverchok the root module name, (if sverchok dir not named exactly "sverchok")
	if __name__ != "sverchok":
	sys.modules["sverchok"] = sys.modules[__name__]

the same modules can be imported several times. This is bad because some modules can share information between eachother via third modules and if each of them has its own instance of a module then there is no information interchange. In general I think all modules should have only one instance.

Looks like that sverchok name was added to sys.modules so that import path could be started from sverchok name. But it's not clear why relative import paths could not be used instead.

Adding main module reachable by sverchok name makes importing modules peculiar. For example:

__name__ == "svercok-master"  # True
from sverchok.data_structure import DEBUG_MODE
assert('sverchok.data_structure' in sys.modules)  # True

__name__ == "svercok-master"  # True
from sverchok import data_structure
assert('sverchok-master.data_structure' in sys.modules)  # True

I'm not sure yet how this can be handled. Probably adding __name__ = "sverchok" would solve the problem.

Useful links:
https://b3d.interplanety.org/en/creating-multifile-add-on-for-blender/
https://devtalk.blender.org/t/plugin-hot-reload-by-cleaning-sys-modules/20040