import os, sys
def reportdiffs(unique1, unique2, dir1, dir2):
    if not (unique1 or unique2):
		print('Directory lists are identical')
	else:
		if unique1:
			print('Files unique to', dir1)
			for file in unique1:
				print('...', file)
		if unique2:
			print('Files unique to', dir2)
			for file in unique2:
				print('...', file)

def difference(seq1, seq2):
	return [item for item in seq1 if item not in seq2]

def comparedirs(dir1, dir2, files1 = None, files2 = None):
	print('Comparing', dir1, 'to', dir2)
	files1 = os.listdir(dir1) if files1 is None else files1
	files2 = os.listdir(dir2) if files2 is None else files2
	unique1 = difference(files1, files2)
	unique2 = difference(files2, files1)
	reportdiffs(unique1, unique2, dir1, dir2)
	return not (unique1 or unique2)

def getargs():
	try:
		dir1, dir2 = sys.argv[1:]
	except:
		print('Usage: dirdiff.py dir1 dir2')
		sys.exit(1)
	else:
		return (dir1, dir2)

if __name__ == '__main__':
	dir1, dir2 = getargs()
	comparedirs(dir1, dir2)