How to Solve Empty File Upload Issues in FastAPI?

How to Upload File using FastAPI?

Problem:
When using FastAPI to upload a file according to the official documentation, the file2store variable remains empty.

Cause:

• Ensure that python-multipart is installed.
• When using def endpoints, you can use the .file attribute to access the actual Python file and call its methods synchronously.
• When using async def endpoints, consider asynchronous file operations.
• Adjust chunk size accordingly if files are too large for memory.

Solution:

app.py:

from fastapi import File, UploadFile

@app.post("/create_file")
def create_file(file: UploadFile = File(...)):
    try:
        contents = file.file.read()
        # store contents to the database
    except Exception:
        return {"message": "Error uploading file"}
    finally:
        file.file.close()
    return {"message": f"Successfully uploaded {file.filename}"}

Alternative for Async Endpoints:

@app.post("/create_file")
async def create_file(file: UploadFile = File(...)):
    try:
        contents = await file.read()
        # store contents to the database
    except Exception:
        return {"message": "Error uploading file"}
    finally:
        await file.close()
    return {"message": f"Successfully uploaded {file.filename}"}

Uploading Multiple Files:

from fastapi import File, UploadFile
from typing import List

@app.post("/upload")
def upload(files: List[UploadFile] = File(...)):
    for file in files:
        try:
            contents = file.file.read()
            # store contents to the database
        except Exception:
            return {"message": "Error uploading file(s)"}
        finally:
            file.file.close()
    return {"message": f"Successfully uploaded {[file.filename for file in files]}"}

Request from Python Script:

requests.post(url="SERVER_URL/create_file", files={"file": (f.name, f, "multipart/form-data")})

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