Python 2.7 on Windows:
Microsoft Visual C++ 10.0 is required (unable to find vcvarsall.bat)
was formerly fixed by installing Microsoft Visual C++ Compiler for Python 2.7. However, this download is NO LONGER AVAILABLE. It’s recommended in general to use a recent Python 3 version instead.
Visual Studio is used for Python on Windows whenever C, C++, Fortran or other compiled language extension modules are used from Python. For example, a C library may be used for better performance, seamlessly called from Python.