Python3 batch file rename

rename.py

import os
from_path = '/home/nate/Dropbox/muni-17477/'
to_path = '/home/nate/Dropbox/muni-17477-fixed/'
old_files = os.listdir(from_path)
for old_file in old_files:
	old_fpath = from_path+old_file
	with open(old_fpath,'r') as fp:
		old_content = fp.read()
		old_hour = old_file[11:13]
		new_hour =str(int(old_hour)-3)
		new_hour = new_hour.zfill(2)
		new_file = old_file[:11]+new_hour+old_file[13:]
		with open(to_path+new_file,'w+') as newfp:
			newfp.write(old_content)
			print(new_file)