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.
Internally, Django uses a django.core.files.File 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 File attributes and methods documented in The File object.
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.
Jul 05, 2010