This document describes Django’s file access APIs.
By default, Django stores files locally, using the MEDIA_ROOT
and
MEDIA_URL
settings. The examples below assume that you’re using these
defaults.
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.
When you use a FileField
or
ImageField
, Django provides a set of APIs you can use
to deal with that file.
Consider the following model, using an ImageField
to
store a photo:
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')
Any 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: chevy.jpg>
>>> car.photo.name
u'cars/chevy.jpg'
>>> car.photo.path
u'/media/cars/chevy.jpg'
>>> car.photo.url
u'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.
Note
The file is saved as part of saving the model in the database, so the actual file name used on disk cannot be relied on until after the model has been saved.
File
object¶Internally, Django uses a django.core.files.File
instance any time it
needs to represent a file. This object is a thin wrapper around Python’s
built-in file object with some Django-specific additions.
Most of the time you’ll simply use a File
that Django’s given you (i.e. a
file attached to a model as above, or perhaps an uploaded file).
If you need to construct a File
yourself, the easiest way is to create one
using a Python built-in file
object:
>>> from django.core.files import File
# Create a Python file object using open()
>>> f = open('/tmp/hello.world', 'w')
>>> myfile = File(f)
Now you can use any of the documented attributes and methods
of the File
class.
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.
Django’s default file storage is given by the DEFAULT_FILE_STORAGE
setting; if you don’t explicitly provide a storage system, this is the one that
will be used.
See below for details of the built-in default file storage system, and see Writing a custom storage system for information on writing your own file storage system.
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.storage import default_storage
>>> from django.core.files.base import ContentFile
>>> path = default_storage.save('/path/to/file', ContentFile('new content'))
>>> path
u'/path/to/file'
>>> default_storage.size(path)
11
>>> default_storage.open(path).read()
'new content'
>>> default_storage.delete(path)
>>> default_storage.exists(path)
False
See File storage API for the file storage API.
Django ships with a built-in FileSystemStorage
class (defined in
django.core.files.storage
) which implements basic local filesystem file
storage. Its initializer takes two arguments:
Argument | Description |
---|---|
location |
Optional. Absolute path to the directory that will
hold the files. If omitted, it will be set to the
value of your MEDIA_ROOT setting. |
base_url |
Optional. URL that serves the files stored at this
location. If omitted, it will default to the value
of your MEDIA_URL setting. |
For example, the following code will store uploaded files under
/media/photos
regardless of what your MEDIA_ROOT
setting is:
from django.db import models
from django.core.files.storage import FileSystemStorage
fs = FileSystemStorage(location='/media/photos')
class Car(models.Model):
...
photo = models.ImageField(storage=fs)
Custom storage systems work the same way:
you can pass them in as the storage
argument to a
FileField
.
Oct 11, 2017