windows下unable to find vcvarsall.bat解决

python -m pip install -U pip

def (version):
    productdir = 'C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat'
    vcvarsall = os.path.join(productdir)
    if os.path.isfile(vcvarsall):
        return vcvarsall
    else:
        return None