import os, Image, math list_files_jpg = [file_name for file_name in os.listdir('.') if file_name.endswith(".jpg")] for i in list_files_jpg: im=Image.open(i) factor=im.size[0]/460.0 f=int(math.ceil(im.size[1]/factor)) out=im.resize((460,f)) newname=i.split(".")[0]+"_r.jpg" out.save(newname)