Malformed request from aiohttp.ClientSession().post() with multiple image files - python-asyncio

Question

I'm still relatively new to Python and my first time to use aiohttp so I'm hoping someone can help spot where my problem is.
I have a function that does the following:
retrieves from the JSON payload two base64 strings - base64Front and base64Back
decode them, save to "images" folder
send the Front.jpg and Back.jpg to an external API
this external API expects a multipart/form-data
imgDataF = base64.b64decode(base64FrontStr)
frontFilename = 'images/Front.jpg'
with open(frontFilename, 'wb') as frontImgFile:
frontImgFile.write(imgDataF)
imgDataB = base64.b64decode(base64BackStr)
backFilename = 'images/Back.jpg'
with open(backFilename, 'wb') as backImgFile:
backImgFile.write(imgDataB)
headers = {
'Content-Type': 'multipart/form-data',
'AccountAccessKey': 'some-access-key',
'SecretToken': 'some-secret-token'
}
url = 'https://external-api/2.0/AuthenticateDoc'
files = [('file', open('./images/Front.jpg', 'rb')),
('file', open('./images/Back.jpg', 'rb'))]
async with aiohttp.ClientSession() as session:
async with session.post(url, data=files, headers=headers) as resp:
print(resp.status)
print(await resp .json())
The response I'm getting is status code 400 with:
{'ErrorCode': 1040, 'ErrorMessage': 'Malformed/Invalid Request detected'}
If I call the url via Postman and send the two jpg files, I get status code 200.
Hope someone can help here.
Thanks in advance.

Answer 1

Try using FormData to construct your request. Remove the content type from header and use it in FormData field as below:
data = FormData()
data.add_field('file',
open('Front.jpg', 'rb'),
filename='Front.jpg',
content_type='multipart/form-data')
await session.post(url, data=data)
Reference: https://docs.aiohttp.org/en/stable/client_quickstart.html#post-a-multipart-encoded-file