Why i'm unable to open twice a django-uploded-file?

Question

I would like to open an uploaded file in a validator to make sure the file is good, then if it's good re-open it in my view function to extract the data.

I'm not sure if it supposed to be done like that. Tell me what you think.

Here is my validator at it's simple state:

def validate_file(value):
    with value.open("r") as sf:
        pass  # do some checks with the data
    # now the file is closed

and this is my view function :

def home(request):
    if request.method == 'POST':
        # create 2 form
        form_message = Filtre_message_form(request.POST)
        form_spatial = Filtre_spatial_form(request.POST, request.FILES)

        if all((form_message.is_valid(), form_spatial.is_valid())):
            # if the file is good open it
            f = request.FILES['file'].open(mode='r')
            # do some stuf with it

    else:
        # create 2 empty form
        form_message = Filtre_message_form()
        form_spatial = Filtre_spatial_form()
    return render(request, 'home.html', locals())

And i get this error ValueError: I/O operation on closed file.

Here is the error stack :

Traceback (most recent call last):
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\base.py", line 126, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\base.py", line 124, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "H:\workspace\test_Django\django_test\app_test\views.py", line 16, in home
    f = request.FILES['file'].open(mode='r')
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\files\uploadedfile.py", line 87, in open
    self.file.seek(0)
ValueError: I/O operation on closed file.

I've tried this :

def validate_file(value):
   sf = value.open("r")
   # this dosen't close the file

and this works, but in reality i use this lib to read and parse the data. So using the lib the validator look like this:

def validate_file(value):
    import shapefile
    sf = shapefile.Reader(shp=value)

and this dosen't work, here is the error stack :

Internal Server Error: /accueil/
Traceback (most recent call last):
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
    response = get_response(request)
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\base.py", line 126, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\handlers\base.py", line 124, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "H:\workspace\test_Django\django_test\app_test\views.py", line 16, in home
    f = request.FILES['file'].open(mode='r')
  File "H:\workspace\test_Django\venv\lib\site-packages\django\core\files\uploadedfile.py", line 87, in open
    self.file.seek(0)
ValueError: I/O operation on closed file.

I don't understant why i can't open the file a second time ? The library apparently close the file, so why I'm unnable to open it a second time ?

Can you help me please?

what's the purpose of `f = request.FILES['file'].open(mode='r')` in the first place? You do nothing at all after that. also note that the file is an UploadedFile object so you might want to have a look at [the methods described here](https://docs.djangoproject.com/en/2.1/ref/files/uploads/#uploaded-files) — dirkgroten, Mar 28 '19 at 15:14
this is a simplifcation, i would like to read the file with the same lib (shapefile) to extract all of the data — jean-loup Monnier, Mar 29 '19 at 08:06

Why i'm unable to open twice a django-uploded-file?

0 Answers0