What does it mean when people say CPython is written in C?

Question

From what I know, CPython programs are compiled into intermediate bytecode, which is executed by the virtual machine. Then how does one identify without knowing beforehand that CPython is written in C. Isn't there some common DNA for both which can be matched to identify this?

Answer 1

The interpreter is written in C.

It compiles Python code into bytecode, and then an evaluation loop interprets that bytecode to run your code.

You identify what Python is written in by looking at it's source code. See the source for the evaluation loop for example.

Note that the Python.org implementation is but one Python implementation. We call it CPython, because it is implemented in C. There are other implementations too, written in other languages. Jython is written in Java, IronPython in C#, and then there is PyPy, which is written in a (subset of) Python, and runs many tasks faster than CPython.