Unable to find vcvarsall.bat when installing gmpy using pip

GMPY is a multiple-precision arithmetic module, which is a extension module written by C. I tried to install it by using pip, then I got following error message:

Unable to find vcvarsall.bat

It's because it's trying to find a c compiler (Visual C++ or MinGW) to compile this extension but failed. To fix this error, one method is to install a C compiler (Visual C++ or MinGW). And another easier way is to download an windows installer: https://code.google.com/p/gmpy/downloads/list