However, Django provides ways to write custom file storage systems that allow you to completely customize where and how Django stores files. The second half of this document describes how these storage systems work.
Using files in models
from django.db import models class Car(models.Model): name = models.CharField(max_length=255) price = models.DecimalField(max_digits=5, decimal_places=2) photo = models.ImageField(upload_to='cars')
Car instance will have a
photo attribute that you can use to get at the details of the attached photo:
>>> car = Car.objects.get(name="57 Chevy") >>> car.photo <ImageFieldFile: cars/chevy.jpg> >>> car.photo.name 'cars/chevy.jpg' >>> car.photo.path '/media/cars/chevy.jpg' >>> car.photo.url 'http://media.example.com/cars/chevy.jpg'
This object –
car.photo in the example – is a
File object, which means it has all the methods and attributes described below.
>>> import os >>> from django.conf import settings >>> initial_path = car.photo.path >>> car.photo.name = 'cars/chevy_ii.jpg' >>> new_path = settings.MEDIA_ROOT + car.photo.name >>> # Move the file on the filesystem >>> os.rename(initial_path, new_path) >>> car.save() >>> car.photo.path '/media/cars/chevy_ii.jpg' >>> car.photo.path == new_path True
ImageFieldnon-image data attributes, such as
sizeare available on the instance, the underlying image data cannot be used without reopening the image. For example:
>>> from PIL import Image >>> car = Car.objects.get(name='57 Chevy') >>> car.photo.width 191 >>> car.photo.height 287 >>> image = Image.open(car.photo) # Raises ValueError: seek of closed file. >>> car.photo.open() <ImageFieldFile: cars/chevy.jpg> >>> image = Image.open(car.photo) >>> image <PIL.JpegImagePlugin.JpegImageFile image mode=RGB size=191x287 at 0x7F99A94E9048>
If you need to construct a
File yourself, the easiest way is to create one using a Python built-in
>>> from django.core.files import File # Create a Python file object using open() >>> f = open('/path/to/hello.world', 'w') >>> myfile = File(f)
Now you can use any of the documented attributes and methods of the
Be aware that files created in this way are not automatically closed. The following approach may be used to close files automatically:
>>> from django.core.files import File # Create a Python file object using open() and the with statement >>> with open('/path/to/hello.world', 'w') as f: ... myfile = File(f) ... myfile.write('Hello World') ... >>> myfile.closed True >>> f.closed True
Closing files is especially important when accessing file fields in a loop over a large number of objects. If files are not manually closed after accessing them, the risk of running out of file descriptors may arise. This may lead to the following error:
OSError: [Errno 24] Too many open files
Behind the scenes, Django delegates decisions about how and where to store files to a file storage system. This is the object that actually understands things like file systems, opening and reading files, etc.
Though most of the time you’ll want to use a
File object (which delegates to the proper storage for that file), you can use file storage systems directly. You can create an instance of some custom file storage class, or – often more useful – you can use the global default storage system:
>>> from django.core.files.base import ContentFile >>> from django.core.files.storage import default_storage >>> path = default_storage.save('path/to/file', ContentFile(b'new content')) >>> path 'path/to/file' >>> default_storage.size(path) 11 >>> default_storage.open(path).read() b'new content' >>> default_storage.delete(path) >>> default_storage.exists(path) False
The built-in filesystem storage class
For example, the following code will store uploaded files under
/media/photos regardless of what your
MEDIA_ROOT setting is:
from django.core.files.storage import FileSystemStorage from django.db import models fs = FileSystemStorage(location='/media/photos') class Car(models.Model): ... photo = models.ImageField(storage=fs)