Is the primary Python implementation self hosting? Ruby? JavaScript? PHP? Perl? It's common for compiled languages to be self hosted, but less common for script

Is the primary Python implementation self hosting? Ruby? JavaScript? PHP? Perl? It's common for compiled languages to be self hosted, but less common for scripting languages. (Not that Go is a scripting language, just pointing out that many popular languages aren't self hosting.) Even beyond the question of self hosting, I would say that it's rare for much of a scripting language's standard library to be written in that language... especially performance critical parts of the standard library. There would just be too much performance left on the table. The person you're responding to specifically mentioned they came from JavaScript, where the standard library implementations weren't written in JavaScript. (PyPy is a notable exception to this rule of thumb... perhaps as part of its desire to prove how good the JIT is, it seems to be mostly written in Python, which is neat.)