[Python-Dev] Why is Python for Windows compiled with MSVC?

[Oleg Sivokon]

Hello list.

I'll give some background before asking my question in more detail.

I've been tasked with writing some infrastructure code that needs to talk to Kubernetes.  (Kubernetes is a popular software for managing and automating virtualization / containerization of cloud services).  One of the requirements was that the code be written in Python 3.X.

The tasks my code was supposed to perform on Kubernetes would be something like cluster creation from specification, deletion of all or parts of the cluster, providing realtime statistics of cluster usage etc.  There were few prototype scripts written in Bash using kubectl (official client written in Go).

My first reaction was to look for an official client for Kubernetes written in Python. There is one official client for Kubernetes, with a single maintainer, impossible to parse documentation, containing mostly generated code.  It is nigh impossible to use.  Here I need to explain that for whatever reason Kubernetes team decided to write their HTTP API in such a way that the server is "dumb" and the client must be "smart" in order to do anything useful.  For instance, if you have a description of your cluster, you cannot just send this description to the server and hope that it will know how to create the cluster from description.  You need to make multiple API calls (perhaps hundreds of them) to arrange for the server to create the cluster from description.

Since the official client is no help (it really only mirrors the HTTP API), I searched for other clients.  There are two more.  None is in good shape, and none comes even close to being able to do what kubectl can.

There is one more client that shells out calls to kubectl.  It implements only a small subset of kubectl commands, and... it's a lot of parsing of standard output with regular expressions and magic.

Well... I was given a lot of time to investigate other options for dealing with this project, so I decided, what if I can compile kubectl into a shared library and write a Python extension that links against that library.  And, indeed, after few days I came up with such an extension.  It worked!..  On Linux...

Now all I had to do was to re-create my success on Windows (most of the employees in my company use Windows).  At first I thought that I'd cross-compile on Linux using MinGW.  I compiled Go shared library into a DLL, then tried to compile my Python extension and... it didn't work.  I downloaded VirtualBox and some Windows images, etc... tried to compile on Windows.  It didn't work.  I started asking around, and was told that even though for some earlier versions of Python this was kind of possible, for Python 3.5, 3.6 it is not.  You must use MSVC to compile Python extensions.  No way around it.
Now, since Go won't compile with MSVC, I'll have to scrap my project and spend many weeks re-implementing kubectl.

Here's my question: Why?

Why did you choose to use non-free compiler, which also makes cross-compilation impossible?  There wasn't really a reason not to choose MinGW as a way to compile extensions on Windows (Ruby does that, Go uses MinGW, perhaps some others too).  It would've made things like CI and packaging so much easier...  What do Python users / developers get from using MSVC instead?

Thank you.

Oleg
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