Three levels of Python programming

Python programming is not always what we think it is. I now think of Python programming as having three levels, three distinct forms of programming.

The first level is what we typically think of as programming in Python. It is writing Python code. This is the impression one gets when one has an "introduction to Python" class. The first program of "Hello, World" is written in Python, as are the successive programs in the class. Programs become more complex, with the addition of functions and later classes to organize larger and larger programs.

In this level, all of the code is Python. It is Python from top to bottom. And it works, for simple applications.

For some applications, it is not "Python all the way down". Some applications are complex. They must manage large quantities of data, and perform a significant number of calculations, and they must do it quickly. A Python-only solution is not a satisfactory solution, because Python is interpreted and slow.

At this point, programmers include carefully-constructed modules that perform calculations quickly. The modules "numpy" and "scipy" are the common modules, but there are many.

This is the second level of programming in Python. It is not often thought of as "programming in Python" or even "programming". It is more often though of as "importing modules and using the classes and functions in those modules".

That mindset makes sense. This work is less about Python and more about knowing which modules are available and which functions they provide. The task of programming is different; instead of writing all of the code, one assembles a solution from pre-packaged modules and uses Python to connect the various pieces.

That is why I think of it as a second level of programming. It is a different type of programming, a different type of thinking. It is not "how can I write code?" but instead "what existing code will perform this computation?".

Which brings us to the third level.

The third level of Python programming is building your own module. The existing Python modules, if they do what you need, are fast and effective. But if they do not do what you need, then they are not helpful.

Writing your own solution in Python will result is a slow program -- perhaps unacceptably slow. Therefore, as a last resort, one writes one's own module (in C or C++) and imports it into the main Python program.

This is, purists will argue, programming not in Python but in C or C++. They have a point -- it is writing C or C++ code.

But when the objective is to build a system to perform a specific task, and the top layer of the application is written in Python, then one can argue that the C code is merely an extension of the same application.

Or, one can think of the task as creating a system in multiple modules and multiple languages, not a single program in a single programming language, and using the best language for each piece of the system.

Python programming (or systems development) is often less about coding in a particular language and more about solving problems. With Python, we have three levels at which we can solve those problems.