Difference between CPython, Jython, IronPython, PyPy, and Cython

Computer Science is one of the hottest fields out there right now, and it keeps on growing and expanding further. It has tremendously evolved from what it used to be in the early days and now is being used for content that is changing the lives of millions of people. Such has been its advancement that has allowed concepts like artificial intelligence, deep learning, and so many others, which once looked impossible to come into existence.

One particular element of computer science that has seen a large evolution is the programming language section, which is an integral part of machines and comprises instructions that allow the machines to perform different tasks. Python is one high-level programming language that has immensely grown and is being used in multiple sectors of the industry.

However, Python itself is vast and can be implemented in several different flavors, which shall also be the topic of our discussion in this article, and where we will be looking at the different implementations that currently exist of Python.

Different Implementations of Python

We have been using the term “implementation” for a while now. What does this mean? Well, implementation refers to the way the interpreter was written – what languages were used and what is the purpose of that specific interpreter.

Now, let us look at some of the different implementations of Python.

1) CPython

CPython is the default and most widely used interpreter or implementation of Python, written in C. It is the original Python version, which users download from its official website, It can be better described as a mixture of both an interpreter and compiler as it converts your written Python source code into bytecode. By bytecode, we refer to a program code that gets compiled and processed into a low-level language that can be used as instructions for the interpreter. It is this bytecode that gets executed on the CPython Virtual Machine.

Since it is the original Python implementation, CPython has the highest compatibility with a variety of Python packages and modules and is the best choice if users need to write code that completely matches the Python standards.

2) Jython

Jython is another Python implementation that has been written in the Java language whose implementation can run in Java platforms. Similar to CPython, it first converts the source code into bytecode, which, as mentioned before, are a set of instructions that are needed by an interpreter. In Jython, these are written in Java and can run on the Java Virtual Machine, which is the same environment that Java itself uses. Jython allows users to easily work with Java programs since you can call, as well as utilize, your Java functions and classes directly from Jython without any additional effort which is immensely beneficial as Python users can get access into the enormous ecosystem of libraries and frameworks that come along with Java. The same is true on the opposite end.

3) IronPython

Similar to how Jython has been developed for Java users, IronPython is the popular Python implementation that has been written in C-Sharp (C#) and has been designed to run on the .NET platform. It creates a bridge between the Python and .NET universe and allows Python users to get access to C-sharp functions and classes, as well as .NET libraries and frameworks directly from IronPython. IronPython excels for programs that make use of threading and can be found on the website.

4) PyPy

PyPy is the Python implementation that has been written in the Python language itself and is another alternative to CPython. Since it has been created while keeping in mind the specifications of the Python language, it is most compatible with CPython, allowing it to run web frameworks like Django and Flask, and even adds a few improvements on the top of it. PyPy makes use of the concept called Just-in-time (JIT) compilation, which allows it to compile the source code during the execution of the program. This, in turn, has made it several times faster than CPython, in which its runtime speed being slow was a common complaint among users. PyPy completely improves this part of CPython.

5) Cython

Unlike the other implementations of Python mentioned in the list, Cython is not a Python interpreter but rather a superset of the Python language that allows users to compile programs in the C language. The amazing thing is that it provides you with the combined power of both Python and C, and this, therefore, is why it can be used for writing C extensions as well as transform and tune your Python code into C. Hence, Cython overcomes many limitations of Python and still maintains the convenience and comfort that comes with Python.


Python has enormously grown and expanded into various implementations, all of which have been developed to the cater the needs of different users. Throughout the time frame in which users might be working with the Python interface, they might come across several of these implementations, and therefore, it is important to know what exactly each of these is and where does their expertise lie.

About the author

Zeeman Memon

Hi there! I'm a Software Engineer who loves to write about tech. You can reach out to me on LinkedIn.