Export in object format via script. The default cube appears in the scene! I am importing a x3d file and then exporting in obj format using this simple script

import bpy,os

bpy.ops.import_scene.x3d(filepath='field.x3d', axis_forward='Z', axis_up='Y', filter_glob="*.x3d;*.wrl")

bpy.ops.export_scene.obj(filepath='test.obj')


However the resulting obj file contains the default cube! This is the x3d file:



This is the object file after the export:


Why that cube appears ? Does someone know how to avoid the cube in the object file?

Thank you very much for your help!
Have a look at the outliner in your first pic, the cube is there. Just delete the cube and it will no longer be exported. 

Just because it isn't on a visible layer doesn't mean it wont be exported.