Python列表理解仅返回最后一项

Question

I am trying to post multiple files using requests post.

The format that is stated here is:

>>> url = 'http://httpbin.org/post'
>>> multiple_files = [('images', ('foo.png', open('foo.png', 'rb'), 'image/png')),
                      ('images', ('bar.png', open('bar.png', 'rb'), 'image/png'))]
>>> r = requests.post(url, files=multiple_files)
>>> r.text

So I am trying to do this with a list comprehension. But only the last image is uploading. I have a feeling that the comprehension is overriding the images since all images have the same name ' visuals '. But I required all of them to have the name ' visuals '.

images=[list of image URLS]
files=[('visuals',(str(index)+'.jpg',requests.get(image).content,'image/jpeg')) for index,image in enumerate(images)]
requests.post(script.php,files=files)

For example, if there are 20 images, only 20.jpg is sent to my script.php .

Response to answer (not working):

  images=response.xpath(root+'/photos//url/text()').extract()
  visuals=[(str(index)+'.jpg',requests.get(image).content,'image/jpeg') for index,image in enumerate(images)]
  requests.post(triggers,data={'json':json.dumps(array)},files={'visuals':visuals})

Answer 1

The files argument to requests.post is supposed to be a dict . See the example here . Since you pass it with a list object, it will be casted internally to a dict object. During the type casting, a latter element will overwrite the former element with the same key value! Since all element in has the same key "visuals", only the last one will remain in the final dict object.

This question was already answered in requests' issue page #737 .

The list of tuples you provided to data has dict() called on it. Dictionaries (obviously) don't allow duplicate keys, but your list of tuples has duplicate keys, so the last item in the iterable takes the value for that key ... so I'd assume that this is intended behaviour.