Kif tittratta form data u file uploads?

Question

Accepted Answer

FastAPI tittratta **form data** HTML (`Form`) u **file uploads** (`File`/`UploadFile`) — differenti minn JSON bodies, peress li jużaw content types differenti (`multipart/form-data`). Iż-żewġ huma ddikjarati b'parameter types speċjali.

## Form fields

```python
from fastapi import Form

@app.post("/login")
def login(username: str = Form(), password: str = Form()):   # form fields, not JSON
    # data comes as application/x-www-form-urlencoded or multipart/form-data
    return {"username": username}
```

Uża `Form()` biex tirċievi form fields HTML (eż. login form). Nota: rotta tista' tuża jew JSON body **jew** form data, mhux it-tnejn flimkien, peress li huma content types differenti. (Teħtieġ `python-multipart` installat.)

## File uploads

```python
from fastapi import File, UploadFile

@app.post("/upload")
async def upload(file: UploadFile):                  # a single file
    contents = await file.read()                      # read the file's bytes
    file.filename                                      # original name
    file.content_type                                  # MIME type
    # save it:
    with open(f"uploads/{file.filename}", "wb") as f:
        f.write(contents)
    return {"filename": file.filename, "size": len(contents)}
```

`UploadFile` huwa t-tip rrakomandat — file spooled (files kbar jmorru għad-disk, mhux kollu fil-memorja), b'metodi async (`read`, `write`, `seek`) u metadata. Għalxejn imma tiny files, użaha aktar milli raw `bytes`.

## Multiple files u form + file flimkien

```python
@app.post("/upload-many")
async def upload_many(files: list[UploadFile]):       # multiple files
    return [f.filename for f in files]

@app.post("/profile")
async def profile(name: str = Form(), avatar: UploadFile = File()):
    # combine form fields AND a file upload in one multipart request
    ...
```

## Validate uploads (sigurtà!)

```python
if file.content_type not in ["image/jpeg", "image/png"]:   # check type
    raise HTTPException(400, "Invalid file type")
# also: limit file SIZE, sanitize filenames, scan content — uploads are untrusted input
```

## Għaliex huwa importanti

It-trattament ta' form data u file uploads huwa ħtiega komuni u praktika — login forms, profile picture uploads, document submissions, u file-processing APIs kollha jirrikjeduh, u jaħdem b'mod differenti minn JSON bodies li FastAPI juża b'mod default.

Infejm `Form()` għal form fields u speċjalment **`UploadFile`** għal uploads (l-approċċ rrakomandat, peress li jispula files kbar għad-disk rather than iċċargar kulħadd fil-memorja — importanti għal handling ta' files kbar mingħajr exhaustin RAM) huwa neċessarju għal dawn il-features.

Biss bħala importanti huwa r-responsabilità **security** li ġejja ma' uploads: peress li uploaded files huma input untrusted, validating it-type u size tagħhom, sanitizing filenames, u jekk taf kif inti tistennaf/tisservi huma essential biex tevita vulnerabilities.

Infejm kif tirċievi form fields, handle single u multiple file uploads, combine forms ma' files, u validate uploads safe huwa practical knowledge għal building real-world APIs li jaċċettaw user-submitted content.