title: I installed both python 2.7 and 3.5, but python 3.5 does not work well
body: <p>In terminal, I can run <code>py -2</code> successfully.
  Nevertheless, </p>
  
  <pre><code>C:\Users\user&gt;py -3
  Fatal Python error: Py_Initialize: unable to load the file system codec
    File "C:\Python27\lib\encodings\__init__.py", line 123
      raise CodecRegistryError,\
                              ^
  SyntaxError: invalid syntax
  
  Current thread 0x00004570 (most recent call first):
  </code></pre>