error: Unable to find vcvarsall.bat?

Question

I tried to install the Python package [dulwich](https://pypi.python.org/pypi/dulwich):<!-- language-all: lang-none --> pip install dulwichBut I get a cryptic error message: error: Unable to find vcvarsall.batThe same happens if I try installing the package manually: > python setup.py install running build_ext building 'dulwich._objects' extension error: Unable to find vcvarsall.bat

Answer 1

`vcvarsall.bat` appears to be a script to setup environment variables within the Visual Studio C/C++ build system. This library has a binary version which requires compilation of a library written in Rust. This binary version of the library is then bound within python (Via the CTypes built-in library). This binary compilation is why `vcvarsall.bat` is being used and why you are getting an error for not having that file on your system.

To install the pure python version the github repository for Dulwich recommends running this command to install instead:

pip install --no-binary dulwich dulwich --config-settings "--build-option=--pure"