DEGA installation fails on Windows with pythran/OpenBLAS wheel error: how to fix it using WSL/Linux

DEGA pip install fails on Windows with pythran/OpenBLAS wheel errors. See why it occurs and fix it quickly by installing in a Linux environment using WSL.

Installing a Python package can look straightforward until the build system collides with platform constraints. A common case: trying to install DEGA on Windows with pip and running into a wheel build failure that mentions pythran and OpenBLAS. Here’s what’s actually happening and how to get it working without wrestling with your toolchain.

Reproducing the failure

The installation starts normally and then aborts while building the wheel. A typical session in Anaconda Prompt looks like this:

pip install DEGA

The build log highlights two important fragments:

Building wheels for collected packages: DEGA
  Building wheel for DEGA (pyproject.toml) ... error
  error: subprocess-exited-with-error

  × Building wheel for DEGA (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [391 lines of output]
      WARNING: Failed to find 'pythran-openblas' package. Please install it or change the compiler.blas setting. Defaulting to 'none'

Farther down, you may also see:

C:\Users\[user]\AppData\Local\Temp\pip-build-env-xxxx\overlay\Lib\site-packages\setuptools\command\build_py.py:212: _Warning: Package 'DEGA.cython' is absent from the `packages` configuration.

And the process finally aborts with a compiler error:

error: command 'C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.44.35207\bin\HostX86\x64\cl.exe' failed with exit code 2

ERROR: Failed building wheel for DEGA
Failed to build DEGA
ERROR: Failed to build installable wheels for some pyproject.toml based projects (DEGA).

What’s really causing the build to fail

DEGA declares a dependency on pythran, as indicated in its pyproject.toml. The catch is that pythran’s supported platforms are MacOS and POSIX :: Linux; Windows is not supported according to its own project metadata. When the build backend tries to compile DEGA with pythran in a Windows environment, the process cannot complete successfully, and the wheel build fails. The mention of pythran-openblas in the output doesn’t help either, as pythran-openblas is not an actively maintained package.

The practical fix: use a Linux environment on Windows

Since pythran targets Linux and MacOS, the reliable path on a Windows machine is to run the installation inside a Linux environment. On Windows 10 or later, that’s typically Windows Subsystem for Linux (WSL). Microsoft provides a step-by-step guide: How to install Linux on Windows with WSL.

Once you’re in a Linux shell via WSL, install the package the usual way:

pip install DEGA

This approach aligns the build with pythran’s supported platforms and avoids the Windows-specific compiler failure.

Why this matters for Python packaging and builds

Modern Python packages often rely on compiled extensions and build backends defined in pyproject.toml. Those dependencies may encode explicit platform constraints. If a build depends on a toolchain that excludes Windows, no amount of tweaking PATH or reinstalling Visual Studio will change the outcome. Recognizing the platform scope up front saves hours of trial-and-error and points you to the right runtime environment.

Takeaways

If you see a wheel build error for DEGA on Windows that references pythran or pythran-openblas, the core issue is platform support. Run the installation in a Linux environment, such as WSL on Windows, and proceed with pip install there. Before digging into local compilers and SDKs, check the package’s pyproject.toml and the dependency’s supported platforms. It’s the fastest way to match the build system to what the package expects and get on with actual development.