Trying to write standalone Python script for QGIS, can't load SIP

Question

I'm trying to learn to write standalone Python scrips for QGIS, but can't get past first base.

I'm using QGIS 2.18, installed with the OSgeo4W64 installer. I have modified my path as follows.

SET OSGEO4W64_ROOT=C:\OSGeo4W64
SET QGIS_PREFIX=%OSGEO4W64_ROOT%\apps\qgis
SET PATH=%PATH%;%QGIS_PREFIX%\bin
SET PYTHONPATH=%QGIS_PREFIX%\python;%PYTHONPATH%

I'm trying to run a script that begins:

import os, os.path, sys
from qgis.core import *
from qgis.gui import *
from PyQt4.QtGui import *
from PyQt4.QtCore import *

I get the following error:

C:\Users\Steve\Documents\MEGAsync\Steve\Lex>lex.py
Traceback (most recent call last):
  File "C:\Users\Steve\Documents\MEGAsync\Steve\Lex\lex.py", line 3, in <module>
    from qgis.core import *
  File "C:\OSGeo4W64\apps\qgis\python\qgis\__init__.py", line 26, in <module>
    from qgis.PyQt import QtCore
  File "C:\OSGeo4W64\apps\qgis\python\qgis\PyQt\QtCore.py", line 26, in <module>
    import sip
ImportError: DLL load failed: %1 is not a valid Win32 application.

What am I doing wrong?

Answer 1

Finally, all my problems went away with the following.

SET OSGEO4W_ROOT=C:\OSGeo4W64
SET QGIS_PREFIX=%OSGEO4W_ROOT%\apps\qgis
SET PATH=%OSGEO4W_ROOT%\bin;%QGIS_PREFIX%\bin;
SET PYTHONPATH=%QGIS_PREFIX%\python;%OSGEO4W_ROOT%\apps\Python27;%OSGEO4W_ROOT%\apps\Python27\Lib;
SET GDAL_DATA=C:\OSGeo4W64\share\epsg_csv\
python myfile.py