Why Was C Used to Write Python Rather Than C++?

 Why Was C Used to Write Python Rather Than C++?

When it comes to the implementation of programming languages, one question often arises: Why was Python written in C rather than C++? This decision, made in the early 1990s by Guido van Rossum, had profound implications for Python’s growth, simplicity, and adoption. In this article, We will examine the technical, historical, and practical factors that led to this decision in detail in this post, providing developers, programmers, and enthusiasts with a clear understanding of the situation.

Historical Context of Python’s Development

While employed at Centrum Wiskunde & Informatica (CWI) in the Netherlands in the late 1980s, Guido van Rossum started developing Python as an ABC language replacement. He wanted to develop a language for programming that was: 

• Simple to use
• Readable for beginners and experts alike
• Flexible enough for system scripting and broader applications

At that time, C was the dominant systems programming language, offering portability, stability, and efficiency. On the other hand, C++ was still relatively young, evolving rapidly, and not as stable or widely supported.

Portability and Simplicity of C

One of the main reasons C was chosen over C++ is portability. There were C compilers on almost every computer, including mainframes and microcomputers. This made C the ideal candidate for creating an interpreter that could run on multiple platforms without significant modifications.

Additionally, C’s simplicity was an advantage. It provided a thin layer of abstraction over the machine without the complexities of object-oriented paradigms, templates, or advanced type systems that C++ introduced. For building an interpreter core, simplicity was more important than abstraction.

C++ Was Too Complex at the Time

When Python was created, C++ was not as standardized as it is today. It had different dialects, compiler inconsistencies, and evolving features. Using C++ would have introduced unnecessary complexity, making the Python interpreter harder to maintain and less consistent across systems.

Python’s design philosophy emphasizes clarity, readability, and minimalism. Adopting C++ at that time would have gone against these principles, since C++ introduced:

• Multiple inheritance
• Complex class hierarchies
• Template metaprogramming (immature at the time)
• A more complicated compilation model

These features, while powerful, were not aligned with Python’s philosophy of simplicity and straightforwardness.

Alignment with Unix and System Libraries

C was the lingua franca of Unix systems, and most system libraries were written in C. Since Python was intended to serve as a scripting language for system administration and general programming tasks, it made sense to implement it in the same language that dominated Unix environments.

This allowed Python to:

• Interface easily with existing system libraries
• Access low-level functionality without extra layers of complexity
• Remain lightweight and efficient

By writing Python in C, developers could leverage the vast ecosystem of C libraries while keeping the interpreter compact.

C’s Stability vs. C++’s Evolution

Stability was another critical factor. By the early 1990s, C was well-established and had decades of proven use. In contrast, C++ was undergoing rapid evolution, with new features being added and compilers struggling to keep up with the changes.

Python might have encountered the following if it had been written in C++:

• Compatibility issues across platforms
• Frequent rewrites to keep up with evolving standards
• A steeper learning curve for contributors

Using C ensured that the Python interpreter could remain stable and easily understood by a wider audience of developers.

Performance Considerations

Machine code written in C is renowned for being extremely efficient. Since interpreters naturally introduce overhead compared to compiled languages, writing the Python interpreter in C minimized this penalty.

By leveraging C’s low-level memory management and direct control over system resources, Python’s developers ensured that the language remained reasonably performant despite being an interpreted, high-level language.

Ease of Extension with C APIs

One of Python’s strengths is its ability to integrate with external libraries and modules written in C. Python could be implemented in C in the following ways:

• Expose a C API for extending Python
• Allow developers to write performance-critical modules in C
• Enable seamless integration with existing C libraries

This extensibility is one of the reasons why Python became popular in scientific computing, data analysis, and system administration.

Why Not Rewrite Python in C++ Later?

A natural question is: If C++ matured later, why wasn’t Python rewritten in C++?

The answer lies in Python’s community and stability. By the time C++ had become more stable, Python already had a large base of users, contributors, and libraries. Rewriting the interpreter in C++ would have:

• Introduced unnecessary backward compatibility issues
• Risked fragmenting the ecosystem
• Distracted developers from improving the language itself

Instead, the Python community focused on evolving the language (e.g., Python 2 → Python 3 transition) while keeping its C-based interpreter (CPython) as the reference implementation.

Other Implementations Still Exist

Note that there are other Python implementations besides CPython. Other iterations have been created over time, such as: 

• Jython – Python implemented in Java
• IronPython – Python implemented in C# for .NET
• The PyPi project is an implementation of Python written in RPython, a restricted subset of Python.

Despite these alternatives, CPython remains the dominant implementation, largely due to its C foundation, stability, and broad adoption.

Conclusion: Simplicity, Stability, and Portability Won

The decision to implement Python in C rather than C++ was not accidental. It was guided by practical considerations:

• C was stable, portable, and simple
• C++ was immature and overly complex at the time
• C aligned better with Unix systems and libraries
• C enabled extensibility and performance

In the end, this sensible choice contributed to Python's success. By prioritizing simplicity and portability over complexity and abstraction, Python became one of the most popular and versatile programming languages in the world.