Python interpreter

When we write Python code, we get a text file with the .py extension that contains the code. To run the code, we need the Python interpreter to execute the .py file.

Since the entire Python language, from its specifications to its interpreter, is open-source, theoretically, anyone with sufficient expertise can develop a Python interpreter to execute Python code (though this is extremely difficult). In fact, multiple Python interpreters do exist.

CPython

When we download and install Python 3.x from the official Python website, we directly get the official interpreter: CPython. It is developed in the C programming language, hence the name CPython. Running the python command in the command line launches the CPython interpreter.

CPython is the most widely used Python interpreter. All code in this tutorial is executed under CPython.

IPython

IPython is an interactive interpreter built on top of CPython. In other words, IPython only enhances the interactive experience while its Python code execution capability is identical to that of CPython.

CPython uses >>> as its prompt, whereas IPython uses In [line number]: as the prompt.

PyPy

PyPy is another Python interpreter designed for speed. It adopts JIT (Just-In-Time) compilation technology to dynamically compile Python code (note: this is compilation, not interpretation), thus significantly boosting the execution speed of Python code.

Most Python code can run on PyPy, but there are some differences between PyPy and CPython. These differences may lead to inconsistent results when the same Python code is executed on the two interpreters. If you intend to run your code on PyPy, you need to learn about the discrepancies between PyPy and CPython.

Jython

Jython is a Python interpreter that runs on the Java platform. It can directly compile Python code into Java bytecode for execution.

IronPython

Similar to Jython, IronPython is a Python interpreter built for the Microsoft .NET platform. It can directly compile Python code into .NET bytecode.

Summary

There are many Python interpreters available, but CPython remains the most widely used. If you need to interact with the Java or .NET platform, the optimal approach is not to use Jython or IronPython, but to achieve interaction via network calls to ensure the independence of each program.

All code in this tutorial is guaranteed to run only on CPython 3.x. Please make sure to install CPython locally (i.e., the installer downloaded from the official Python website).