I'm not entirely sure if this will fix the issue or not but you can try these commands at IDLE or your python command line of choice.
Note: I actually think you should look at the "possible duplicate" link and rethink your approach. It seems to make more sense than trying to call gdal from the command line. I can never get that to work except when using the OSgeo4W command line.
Mine returns this ...
This tells me that this is the folder Python is looking in for files.
In your case, the comment below indicates your system is looking there. Maybe try putting the file there or try using a complete path to the file ... something like
so then ...