问题
I tried to sole this problem myself for a few days searching on examples and documentations, also it wasn't solved on ruSO. So, I hope that solution will be found here, on enSO.
I develop a service for automatic creation of ads at Vk social network using Python and Google App Engine. Initially, pictures for ads are loaded to my server (part 1), then they are uploaded to Vk server at some time (parts 2.1 and 2.2). It seems that pictures are loaded and stored on my server correctly (I downloaded them and compared with original ones — every byte is the same). But I attach the part 1 code just in case.
To upload a picture to Vk.Ads firstly I need to get a URL — this is simple, so skip it. Secondly, I need to send a POST request to this link with field file with binary content of the photo (API documentation). I created two ways for that (2.1 and 2.2), but both of them returns errcode: 2 which means corrupted file. To my mind, the problem is about the requests, but I don't exclude the possibility of it files uploading/storage on my server, or some strange work of the API. I'll appreciate any answers and comments.
1. Uploading to my server
import webapp2
from google.appengine.ext import ndb
# stores pictures on the server
class Photo(ndb.Model):
name = ndb.StringProperty()
img = ndb.BlobProperty()
@staticmethod
def get(name):
retval = Photo.query(Photo.name == name).get()
return retval
@staticmethod
def create(name, blob):
retval = Photo()
retval.name = name
retval.img = blob
return retval
class PhotosPage(webapp2.RequestHandler):
def get(self):
# general content of the page:
html = '''<form action="/photos" method="post" enctype="multipart/form-data">
<input type="file" name="flimg"/>
<input value="new_pic" name="flname"/>
<input type="submit" value="Upload"/> </form>'''
def post(self):
n = str(self.request.get('flname'))
f = self.request.get('flimg')
p = Photo.get(n)
if p:
p.img = f
else:
p = Photo.create(n, f)
p.put()
2.1. POST to API, approach #1, using urlfetch и poster:
from poster.encode import multipart_encode, MultipartParam
from google.appengine.api import urlfetch
name = 'file'
content = ... # file binary content
where = ... # gotten URL
options = {
'file': MultipartParam(
name=name,
value=content,
filename=name,
filetype='image/png',
filesize=len(content))
}
data, headers = multipart_encode(options)
pocket = "".join(data)
result = urlfetch.fetch(
url=where,
payload=pocket,
method=urlfetch.POST,
headers=headers)
2.2. POST to API, approach #2, using requests:
import requests
name = 'file'
content = ... # file binary content
where = ... # gotten URL
# I also tried without this dict; is it necessary?
data = {
'fileName': name,
'fileSize': len(content),
'description': 'undefined',
}
result = requests.post(where, files={name: StringIO(content)}, data=data)
In addition, for the second approach I extracted the content of my request:
POST
https://pu.vk.com/c.../upload.php?act=ads_add&mid=...&size=m&rdsn=1&hash_time=...&hash=...&rhash=...&api=1
Content-Length: 15946
Content-Type: multipart/form-data; boundary=b4b260eace4e4a7082a99753b74cf51f
--b4b260eace4e4a7082a99753b74cf51f
Content-Disposition: form-data; name="description"
undefined
--b4b260eace4e4a7082a99753b74cf51f
Content-Disposition: form-data; name="fileSize"
15518
--b4b260eace4e4a7082a99753b74cf51f
Content-Disposition: form-data; name="fileName"
file
--b4b260eace4e4a7082a99753b74cf51f
Content-Disposition: form-data; name="file"; filename="file"
< File binary content >
--b4b260eace4e4a7082a99753b74cf51f--
UPDATE.
Thanks to SwiftStudier, I found the origin of the problem: StringIO and BytesIO don't behave identical to file open. If I use just open the code works well, but it doesn't with virtual file. How it can be solved?
import requests
from io import BytesIO
with open('path.to/file.png', 'rb') as fin:
content = BytesIO(fin.read())
token = '...'
url = 'https://api.vk.com/method/ads.getUploadURL?access_token=' + token + '&ad_format=2'
upload_url = requests.get(url).json()['response']
post_fields = {
'access_token': token
}
data_fields = {
# This works:
# 'file': open('path.to/file.png', 'rb')
# But this does not:
'file': content
}
response = requests.post(upload_url, data=post_fields, files=data_fields)
print(response.text)
回答1:
Not sure if it can help, but I'll post it anyway
I used requests to upload an image to ads
import requests
token = '***'
url = f'https://api.vk.com/method/ads.getUploadURL?access_token={token}&ad_format=1' # I set add_format randomly just to avoid an error of this parameter was missing
upload_url = requests.get(url).json()['response']
post_fields = {
'access_token': token
}
data_fields = {
'file': open('/path/to/image.png', 'rb')
}
response = requests.post(upload_url, data=post_fields, files=data_fields)
print(response.text)
The result looks like valid photo upload, the data received can be used in further actions with ad API.
回答2:
After a lot of experiments and investigating of different HTTP requests content I found out the only difference between wrong and working code. It was about 4 bytes only: file name MUST contain the extension. Vk API even ignores Content-Type: image/png, but needs .png or similar in filename. So, this doesn't work:
requests.post(upload_url, files={
'file': BytesIO('<binary file content>')
})
But this option works properly:
requests.post(upload_url, files={
'file': ('file.png', BytesIO('<binary file content>'), 'image/png')
})
Just like this one, which is not available for GAE:
requests.post(upload_url, files={
'file': open('/path/to/image.png', 'rb')
})
Both StringIO and StringIO are appropriate for that task. As mentioned, Content-Type does not matter, it can be just multipart/form-data.
来源：https://stackoverflow.com/questions/47908968/python-app-engine-http-multipart-post-to-vk-ads-api