[Sasuraigar]

My roommate and I modified the original code in the pastebin to be shorter, and to account for spaces in directories and filenames. Enjoy.

import os
import subprocess
import sys
import datetime
import argparse

def abs_file_paths(directory):
	for dirpath,_,filenames in os.walk(directory):
		for f in filenames:
			yield os.path.abspath(os.path.join(dirpath, f))



def main():
	#list of available formats to convert
	formats = [ 'epub', 'mobi', 'html', 'lit', 'rtf', 'txt', 'odt', 'pdf' ]
	
	#parse command line arguments
	ap = argparse.ArgumentParser(description='Batch convert between ebook formats.')
	ap.add_argument('--have', action='store', default='epub', choices=formats)
	ap.add_argument('--want', action='store', default='mobi', choices=formats)
	ap.add_argument('-s', '--src', default=os.getcwd())
	args = ap.parse_args()

	#Switch dirs to absolute paths
	src = os.path.abspath(args.src)

	#add period and string-ify things to be safe
	have = "." + str(args.have)
	want = "." + str(args.want)

	files = abs_file_paths(src)
	for f in files:
		if f.endswith(have):
			outfile = f[:-len(have)] + want
			if not os.path.exists(outfile):
				print("converting \ninfile=%s\noutfile=%s" % (f, outfile))
				subprocess.call(['ebook-convert', f, outfile])
			

if __name__ == '__main__':
	main()