# encoding:UTF-8
# Listing 9-10. Making a Script a Module
'''
If you wanted to turn chext.py into a module that could also be used from other modules, you could put this code into a 
function and separate its use as a script like this:
'''
import sys
import os
def change_ext(directory, old_ext, new_ext):
	for f in os.listdir(directory):
		base, ext = os.path.splitext(f)
		if ext[1:] == old_ext:
			os.rename(f, "%s.%s" % (base, new_ext))

if __name__ == '__main__':
	if len(sys.argv) < 4:
		print("usage: %s directory old_ext new_ext" % sys.argv[0])
		sys.exit(1)
	change_ext(sys.argv[1], sys.argv[2], sys.argv[3])

'''
python chext.py . foo java
OR 
jython chext.py  . foo java
'''