import os
train_path = "animals/train/"

i = 0
for dir in os.listdir(train_path):
    full_path = os.path.join(train_path, dir)
    for filename in os.listdir(full_path):
        # rename from 00000
        new_filename = f"{str(i).zfill(5)}.{filename.split('.')[-1]}"

        old_file = os.path.join(full_path, filename)
        new_file = os.path.join(full_path, new_filename)

        os.rename(old_file, new_file)
        i += 1