Python 3.x scrapy.pipeline ImagePipeline func文件路径。当我回来的时候

imagepipiline中的函数文件_path参数将响应。当我直接返回str时，我可以成功下载图像。如果使用response.meta.get（'file_name'），下载将失败。它也是一个字符串。为什么不能使用变量

item.py-

test.py-

管道.py-

当我运行它时，它成功了！结果如下：

response.file_name:yoxo.jpg
<class 'str'>
yoxo.jpg
response.file_name:yoxo.jpg
<class 'str'>
yoxo.jpg

结果:

2018-12-13 22:11:39 [scrapy.core.scraper] WARNING: Dropped: Image Downloaded Failed
{'file_name': 'yoxo.jpg',
 'url': 'https://zmtimg.dfcfw.com/529d2d0f7a57c9135eb956b9afa1810a.em/art'}

2018-12-13 22:15:31 [root] ERROR: None
2018-12-13 22:15:31 [root] ERROR: 'NoneType' object has no attribute 'meta'
2018-12-13 22:15:31 [scrapy.core.scraper] WARNING: Dropped: Image Downloaded Failed
{'file_name': 'yoxo.jpg',
 'url': 'https://zmtimg.dfcfw.com/529d2d0f7a57c9135eb956b9afa1810a.em/art'}

我用下面的代码进行了尝试。结果是空的，为什么？同样是第一个响应的正常返回，写在try之外的是空的

try:
    # aa = response.meta.get('file_name')
    print('response.file_name:{}'.format(response.meta.get('file_name')))
    print(type(response.meta.get('file_name')))
    print(response.meta.get('file_name'))
except Exception as e:
    logging.error(response)
    logging.error(e)
    pass
print(response.meta.get('file_name','yep'))
return 'hello.jpg'

结果:

2018-12-13 22:11:39 [scrapy.core.scraper] WARNING: Dropped: Image Downloaded Failed
{'file_name': 'yoxo.jpg',
 'url': 'https://zmtimg.dfcfw.com/529d2d0f7a57c9135eb956b9afa1810a.em/art'}

2018-12-13 22:15:31 [root] ERROR: None
2018-12-13 22:15:31 [root] ERROR: 'NoneType' object has no attribute 'meta'
2018-12-13 22:15:31 [scrapy.core.scraper] WARNING: Dropped: Image Downloaded Failed
{'file_name': 'yoxo.jpg',
 'url': 'https://zmtimg.dfcfw.com/529d2d0f7a57c9135eb956b9afa1810a.em/art'}

为什么？我不明白。非常感谢你的帮助

try:
    # aa = response.meta.get('file_name')
    print('response.file_name:{}'.format(response.meta.get('file_name')))
    print(type(response.meta.get('file_name')))
    print(response.meta.get('file_name'))
except Exception as e:
    logging.error(response)
    logging.error(e)
    pass
print(response.meta.get('file_name','yep'))
return 'hello.jpg'

2018-12-13 22:15:31 [root] ERROR: None
2018-12-13 22:15:31 [root] ERROR: 'NoneType' object has no attribute 'meta'
2018-12-13 22:15:31 [scrapy.core.scraper] WARNING: Dropped: Image Downloaded Failed
{'file_name': 'yoxo.jpg',
 'url': 'https://zmtimg.dfcfw.com/529d2d0f7a57c9135eb956b9afa1810a.em/art'}