When you use pip to install your package, if a wheel is available for your version of Python, it will be downloaded and extracted. Extension modules included in wheels have already been compiled, so you do not need a compiler on the machine you are installing onto. For Windows platforms, a package developer can upload wheels of their packages as well as the source code. The good news is that the culture is changing. Because Windows has a different culture, most people do not have (or need) a compiler. So the culture is one where only source code is distributed, and every machine is set up with a compiler and the tools necessary to build extension modules on install. This makes it impossible to precompile programs and only distribute the build outputs, because many users will not be able to use it. However, Python comes from a very different world where every single machine can be different and incompatible. This is largely due to the very impressive compatibility that Windows provides – you can take a program that was compiled twenty years ago and run it on versions of Windows that nobody had imagined at that time. “vcvarsall.bat” is part of the compiler in Visual Studio that is necessary to compile the module.Īs a Windows user, you’re probably used to downloading programs that are ready to run.
When you see “unable to find vcvarsall.bat”, it means you’re installing a package that has an extension module, but only the source code. In many cases the extension module is an internal detail all the classes and functions you’re actually using have been written in Python, but the tricky parts or the high-performance parts are in the extension module. pyd files that contain native, platform-specific code, typically written in C. py files containing Python source code – they are. The answer is that they include extension modules, sometimes called native modules.
But how can these packages do things that aren’t possible in regular Python?
Like image processing with Pillow, high-performance machine learning with scikit-learn, or micro-threading with greenlet. One of the benefits of installing a separate package is the ability to do something that you couldn’t normally do – in many cases, this is something that would be completely impossible otherwise. To explain why we need this tool, we need to look at a common pattern in Python packages. What is vcvarsall.bat, and why do I need it? What is this mythical batch file? Why do I need it? Where can I get it? How do I help Python find it? When will we be freed from this pain? Let’s look at some answers to these questions. One of the most common errors you’ll see is this one:Īs far as errors go, “unable to find vcvarsall.bat” is not the most helpful. Python’s packaging ecosystem is one of its biggest strengths, but Windows users are often frustrated by packages that do not install properly.
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