"Can't find Python executable" when I tried to install an angular 2 application.

Dear experts here, I am learning angular 2 these days. When I tied to run "npm install" on an angular 2 application for displaying a slider document, it threw me into an error about python. I have two versions of python installed, how could I set up %PYTHON% PARAMETER?

THANKS.

C:\angular-training-slides\slides\node_modules\bufferutil>if not defined npm_config_node_gyp (node "C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\bin\node-gyp-bin\\..\..\node_modules\node-gyp\bin\node-gyp.js" rebuild )  else (node "" rebuild )
gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "C:UsersjyuAppDataLocalProgramsPythonPython35python.EXE", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\node-gyp\lib\configure.js:454:19)
gyp ERR! stack     at PythonFinder.<anonymous> (C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\node-gyp\lib\configure.js:480:16)
gyp ERR! stack     at C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\graceful-fs\polyfills.js:284:29
gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:114:15)
gyp ERR! System Windows_NT 6.1.7601
gyp ERR! command "C:\\Program Files\\nodejs\\node.exe" "C:\\Users\\jyu\\AppData\\Roaming\\npm\\node_modules\\npm\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild"
gyp ERR! cwd C:\angular-training-slides\slides\node_modules\bufferutil
gyp ERR! node -v v7.7.4
gyp ERR! node-gyp -v v3.5.0
gyp ERR! not ok

> utf-8-validate@1.2.2 install C:\angular-training-slides\slides\node_modules\utf-8-validate
> node-gyp rebuild


C:\angular-training-slides\slides\node_modules\utf-8-validate>if not defined npm_config_node_gyp (node "C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\bin\node-gyp-bin\\..\..\node_modules\node-gyp\bin\node-gyp.js" rebuild )  else (node "" rebuild )
gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "C:UsersjyuAppDataLocalProgramsPythonPython35python.EXE", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\node-gyp\lib\configure.js:454:19)
gyp ERR! stack     at PythonFinder.<anonymous> (C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\node-gyp\lib\configure.js:480:16)
gyp ERR! stack     at C:\Users\jyu\AppData\Roaming\npm\node_modules\npm\node_modules\graceful-fs\polyfills.js:284:29
gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:114:15)
gyp ERR! System Windows_NT 6.1.7601
gyp ERR! command "C:\\Program Files\\nodejs\\node.exe" "C:\\Users\\jyu\\AppData\\Roaming\\npm\\node_modules\\npm\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild"
gyp ERR! cwd C:\angular-training-slides\slides\node_modules\utf-8-validate
gyp ERR! node -v v7.7.4
gyp ERR! node-gyp -v v3.5.0
gyp ERR! not ok
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\chokidar\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.1.1: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: bufferutil@1.2.1 (node_modules\bufferutil):
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: bufferutil@1.2.1 install: `node-gyp rebuild`
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: Exit status 1
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: utf-8-validate@1.2.2 (node_modules\utf-8-validate):
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: utf-8-validate@1.2.2 install: `node-gyp rebuild`
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: Exit status 1