[z92]

The lookup thing only happens during compilation to byte code or intermediate code, I believe. Once in byte code, there are no variable names, only addresses.

[klmr]

No, unfortunately that is not the case. Lookup happens at execution of the byte code, because variables cannot be looked up at byte compilation. Consider the following case:

    x = 1
    local({
        assign(user_input, 2)
        print(x)
    }, envir = new.env(parent = environment()))

If `user_input` is “x”, the lookup of `x` in the local scope finds a different variable, in a different scope. Hence this lookup needs to take place every time this piece of code is executed.

I’m not sure if Python suffers from similar problems.