Change file extension for multi file in sub-folder

changeext.py

import os
 
def change_file_ext(cur_dir, old_ext, new_ext, sub_dirs=False):
    if sub_dirs:
        for root, dirs, files in os.walk(cur_dir):
            for filename in files:
                file_ext = os.path.splitext(filename)[1]
                if old_ext == file_ext:
                    oldname = os.path.join(root, filename)
                    newname = oldname.replace(old_ext, new_ext)
                    os.rename(oldname, newname)
    else:
        files = os.listdir(cur_dir)
        for filename in files:
            file_ext = os.path.splitext(filename)[1]
            if old_ext == file_ext:
                newfile = filename.replace(old_ext, new_ext)
                os.rename(filename, newfile)
change_file_ext('C:/Users/xxxx/Desktop/abc', '.html', '.txt', True)

Credit:https://gomputor.wordpress.com/2008/09/29/change-the-extension-of-multiple-files-in-a-chosen-directory-with-python/