If you write a program in python, say a hello world:

'

def hello_world():

  print("hello, world")

Is that not python? Yet it uses a subset of python?

That program can be run by either a python runtime, or a python subset runtime.

Now if you were to run a python subset program, like a hello world, you would get:

'

def hello_world():

  print("hello, world")

Whoah, it's the same thing.

Turns out every program you write with a subset of a language, is valid for the super language.

Subjectively also, if the subset is big enough, it feels like that language, if it uses 'def' for functions, that's python. 'I know it when I see it' kinda deal.

I think the confusion comes from the mathematical folk reading "subset of X is X", and implying that "subset of X=X". But this is natural language, not mathematical language, when I say that "dog is mammal", I'm not saying that "dog = mammal" I'm saying that "dog ∈ mammal", and "subset of python ∈ python"