In general I think this is a good idea. Both for performance reasons as well as for CPython compliance. Is there any limit to the amount of strings which are interned?

I don't think so. I have not looked deeply at the CPython implementation yet, but it seems like the vast majority of compile-time constants (apart from some exceptions) are interned. I'm not sure if any strings are interned at runtime.

https://rushter.com/blog/python-strings-and-memory/

function and class names
variable names
argument names
constants (all strings that are defined in the code)
keys of dictionaries
names of attributes

Strings passed to sys.intern() are, but the VM doesn't decide to intern any strings other than constants.

Good point https://docs.python.org/3/library/sys.html#sys.intern

@coolreader18 implemented it