陷阱： image length is zero in trainning dataset

就 keras 的 cats and dogs.
出現：

PIL.UnidentifiedImageError: cannot identify image file

google 一下，有人說用

import os
from PIL import Image
folder_path = 'data\img'
extensions = []
for fldr in os.listdir(folder_path):
    sub_folder_path = os.path.join(folder_path, fldr)
    for filee in os.listdir(sub_folder_path):
        file_path = os.path.join(sub_folder_path, filee)
        print('** Path: {}  **'.format(file_path), end="\r", flush=True)
        im = Image.open(file_path)
        rgb_im = im.convert('RGB')
        if filee.split('.')[1] not in extensions:
            extensions.append(filee.split('.')[1])

檢查 image 是不是合格。
果然，出現：

Traceback (most recent call last):in/cats/666.jpg  **
  File "checkimage.py", line 10, in 
    im = Image.open(file_path)
  File "/home/charles-chang/miniconda3/envs/tensorflow-gpu/lib/python3.8/site-packages/PIL/Image.py", line 2967, in open
    raise UnidentifiedImageError(
PIL.UnidentifiedImageError: cannot identify image file './cats_and_dogs_small/train/cats/666.jpg'

用 mediainfo 看 666.jpg，沒有內容。一看 file size 是 0

再加上 666 來 google ，出現這一篇。
甚至把影像都看一下，確認真的是 Cats, Dogs，發現有些不正確的影像...