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Aug 25, 2017

How to Upload Files With Django

Pasha Volkov
Pasha Volkov

There are several approaches to uploading files in Django. Each developer faces the most obvious one regularly, when a regular file upload field is used, and it has some known disadvantages. Namely, in case of validation errors the file upload field is reset and the user is forced to select the file again, which is quite tedious. Moreover, in the modern interfaces it is often needed to see the upload result in the form immediately, especially when it comes to the image or when the form is sent with Ajax.

In this article, we will look at two main alternative approaches to the file uploading process:

  • Using a separate upload handler and sending a file with ajax
  • Using a separate file model and fk storing

We will omit the implementation details of the files uploading process on the client side, since it depends heavily on the frontend framework used, and focus on the backend. In any case, the file should be sent using a POST request and included into the request.FILES dictionary on the django side. So:

Handle file upload with separate view

Generally, with this approach, when a file is sent and saved, a disk path is returned, and this path is used as the string value in the corresponding field of the form. No significant changes of the model are required, and the whole front-end task is reduced to sending file to the server after selecting it, processing the response, and substituting the result in the required field. At the same time, a classic example from the django documentation suggests doing the following:

# forms.py
from django import forms

class UploadFileForm(forms.Form):
    title = forms.CharField(max_length=50)
    file = forms.FileField()

#views.py
from django.http import HttpResponseRedirect
from django.shortcuts import render
from .forms import UploadFileForm

# Imaginary function to handle an uploaded file.
def handle_uploaded_file(f):
    with open('some/file/name.txt', 'wb+') as destination:
        for chunk in f.chunks():
            destination.write(chunk)

def upload_file(request):
    if request.method == 'POST':
        form = UploadFileForm(request.POST, request.FILES)
        if form.is_valid():
            handle_uploaded_file(request.FILES['file'])
            return HttpResponseRedirect('/success/url/')
    else:
        form = UploadFileForm()
    return render(request, 'upload.html', {'form': form})

This is a too low-level approach and it has obvious drawbacks:

  • You have to manually write the path to save the file
  • You work with a file object directly
  • The original file name is not used while saving

It is much easier and more convenient to use the built-in django tools to work with the storage - default_storage. The above example can be transformed as follows:

#views.py
Import os

from django.conf import settings


def file_upload(request):
    save_path = os.path.join(settings.MEDIA_ROOT, 'uploads', request.FILES['file'])
    path = default_storage.save(save_path, request.FILES['file'])
    return default_storage.path(path)

With this approach, the following advantages are obvious:

  • The file is saved in the location specified in the settings.
  • The integrated mechanism manages the file saving

As a result, we can get all the necessary data and pass it to the frontend

So, if we need to upload a picture, we can immediately get a link to it and send json to the client side to display the image immediately after uploading, or use it for the further processing (crop, filters, etc.)

Handle file upload with file model

In some cases, you need to store additional information about the uploads: who, when uploaded it and so on. For this purpose it makes sense to create a separate model for storing such data and make a link to it in the main model with the foreign key:

#models.py
from django.db import models


class Document(models.Model):
    upload_by = models.ForeignKey('auth.User', related_name='uploaded_documents')
    datestamp = models.DateTimeField(auto_now_add=True)
    document = models.Field(upload_to='uploads/')
    # ...


class MainModel(models.Model):
    title = models.CharField(max_length=42)
    document = models.ForeignKey(Document)
    #...

Then, our view that deals with processing of file uploads can be modified as follows:

#views.py
Import os

from django.conf import settings
from django.http import JsonResponse
from django.views.decorators.http import require_POST

@require_POST
def file_upload(request):
    save_path = os.path.join(settings.MEDIA_ROOT, 'uploads', request.FILES['file'])
    path = default_storage.save(save_path, request.FILES['file'])
    document = Document.objects.create(document=path, upload_by=request.user)
    return JsonResponse({'document': document.id})

And on the frontend we will fill not the file field, but the object id field for the ForeignKey.

Conclusion

Both of these methods allow you to handle files upload more flexibly and bypass the unpleasant limitation with resetting the file upload field.

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