What is a Django File Object?

I. What is a Django File Object?

Django abstracts a set of “file handling systems”. The core concept is:

django.core.files.File: The base class for all file-related classes in Django.

It provides a unified interface for:

• Reading
• Writing
• Iterating
• Saving to a Storage backend (local disk, OSS, S3, etc.)

Used with FileField / ImageField:

python

class MyModel(models.Model):
    file = models.FileField(upload_to='files/')

This field does not store the file content in the database. It only stores the file path as a string.

The actual file saving is handled by:

1. django.core.files.File (or its subclasses like ContentFile)
2. A Storage system (default is local filesystem).

python

obj.file.save('result.txt', ContentFile('hello world'))

At this point, Django will:

1. Write the ContentFile content to local disk, OSS, S3, etc.
2. Write the saved path to the database field file.

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II. Which Django File Object to Use in Different Scenarios

Scenario 1: User Uploads a File (Common in Web/DRF)

python

def upload(request):
    f = request.FILES['file']  # InMemoryUploadedFile or TemporaryUploadedFile
    print(f.name, f.size, f.content_type)

Scenario 2: Dynamically Generate a File (e.g., CSV/JSON/Image) and Save to a FileField

python

from django.core.files.base import ContentFile
content = "name,age\nTom,18\nJerry,20"
obj.file.save("data.csv", ContentFile(content))

Scenario 3: Save a Locally Opened File (via Python open) to a FileField

python

from django.core.files import File
with open('local.txt', 'rb') as f:
    obj.file.save('copy.txt', File(f))

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III. Configuration for Different File Storage Backends

1. Local Storage: Saving to Server Disk

Django uses local disk storage by default. The class used is:

python

DEFAULT_FILE_STORAGE = 'django.core.files.storage.FileSystemStorage'

In settings.py:

python

import os
BASE_DIR = os.path.dirname(os.path.dirname(__file__))
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')  # Actual file save path
MEDIA_URL = '/media/'  # Browser access prefix

Model configuration:

python

class MyModel(models.Model):
    file = models.FileField(upload_to='uploads/')

Finally, executing:

python

obj.file.save('a.txt', ContentFile('hello'))

Actual Effect:

• File is saved to: MEDIA_ROOT / uploads / a.txt
  • Example: /project_root/media/uploads/a.txt
• The database field stores only the relative path: uploads/a.txt
• Browser access URL is: MEDIA_URL + 'uploads/a.txt' → /media/uploads/a.txt

To access files via URL, add a static route in urls.py:

python

from django.conf import settings
from django.conf.urls.static import static

urlpatterns = [
    # ... your other URLs
] + static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)

2. Cloud Storage: S3/OSS/COS/BOS, etc.

1) Use existing libraries (e.g., django-storages with S3). Installation required:

bash

pip install django-storages boto3

settings.py configuration:

python

INSTALLED_APPS = [
    # ...
    'storages',
]

DEFAULT_FILE_STORAGE = 'storages.backends.s3boto3.S3Boto3Storage'
AWS_ACCESS_KEY_ID = 'Your_Key'
AWS_SECRET_ACCESS_KEY = 'Your_Secret'
AWS_STORAGE_BUCKET_NAME = 'Your_Bucket_Name'
AWS_S3_ENDPOINT_URL = 'https://s3.amazonaws.com'  # For other cloud providers, use their S3-compatible endpoint
MEDIA_URL = 'https://your-bucket-domain/'  # Access URL prefix

Model remains unchanged:

python

class MyModel(models.Model):
    file = models.FileField(upload_to='files/')

Business logic code:

python

obj.file.save('a.txt', ContentFile('hello cloud'))

Django will:

1. Upload the file content to your bucket via S3 API: files/a.txt
2. The database field still stores files/a.txt
3. Page access URL becomes: MEDIA_URL + 'files/a.txt', e.g., https://your-bucket.xxx.com/files/a.txt