How to pass string and multiple files using FastAPI and Python requests?

Question

I am using the following FastAPI endpoint that accepts multiple files:

from fastapi import Request, FastAPI, File, UploadFile
from typing import List
import uvicorn

app = FastAPI()

@app.post("/multiplefiles")
async def _file_upload(keywords, files: List[UploadFile] = File(...)): #create_file
    return {"len_files": keywords}

I would like to first input the keywords parameter, then the list of files, but I cannot find a way to perform a valid post request:

import requests

files = (("keywords", "key1"),
    [
    ('files', open('files\file1.pdf', 'rb')), 
    ('files', open('files\file2.pdf', 'rb'))
    ]
)

response = requests.post('http://127.0.0.1:3000/multiplefiles', files=files)
print(response.json())

If I only upload the files as a list of tuple work, but I do not know how to pass in the keywords parameter.

What is it that you want the requests library to do with the ("keywords", "key1") element? I don't know FastAPI, so looking at the back end def doesn't help me really. — CryptoFool
– CryptoFool, Commented Oct 7, 2022 at 3:21
The keywords are searched in the files, but for the solution I am building I need to pass both keywords and the files with the same call — ardito.bryan
– ardito.bryan, Commented Oct 7, 2022 at 3:23

Chris · Accepted Answer · 2023-05-16 17:57:48Z

Option 1 - Define query parameter as `str`

In the way the keywords parameter is defined in your endpoint is expected to be a query parameter. If you expect it to be a single string value, you can define it using str as follows:

Server side:

@app.post("/")
def upload(keywords: str, files: List[UploadFile] = File(...)):
    return {"keywords": keywords}

Since it is expected as query parameter, you should use the params argument in Python requests, in order to pass query parameters, as described here. Example:

Client side:

url = 'http://127.0.0.1:8000/'
data = {'keywords': 'key1'}
r = requests.post(url, files=files, params=data)
print(r.json())

You could also pass it directly to the URL instead:

url = 'http://127.0.0.1:8000?keywords=key1'

Option 2 - Define query parameter as `List`

If you are sending a list of keywords, you have to declare the keywords query parameter with a type of List (or list in Python 3.9+), and define it explicitly with Query, so that it can receive a list of values, or in other words, to receive multiple values—see related answers here, here and here (for arbitrary query parameters see this and this). Example:

Server side:

from fastapi import Query

@app.post("/")
def upload(keywords: List[str] = Query(...), files: List[UploadFile] = File(...)):
    return {"keywords": keywords}

Client side:

url = 'http://127.0.0.1:8000/'
data = {'keywords': ['key1', 'key2']}
r = requests.post(url, files=files, params=data)
print(r.json())

If you would like to add the list of keywords to the URL's query string yourself, it should then look like this:

url = 'http://127.0.0.1:8000/?keywords=key1&keywords=key2'

See this answer for more details.

Option 3 - Use `Form` parameters

If you would like to use Form parameters instead to pass additional data along with files, please have a look at this answer.

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How to pass string and multiple files using FastAPI and Python requests?

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Option 1 - Define query parameter as `str`

Option 2 - Define query parameter as `List`

Option 3 - Use `Form` parameters

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Option 3 - Use Form parameters

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Option 1 - Define query parameter as `str`

Option 2 - Define query parameter as `List`

Option 3 - Use `Form` parameters