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==============
Managing files
==============
.. versionadded:: 1.0
This document describes Django's file access APIs.
By default, Django stores files locally, using the :setting:`MEDIA_ROOT` and
:setting:`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.
.. _file storage systems: `File storage`_
Using files in models
=====================
When you use a :class:`~django.db.models.FileField` or
:class:`~django.db.models.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.
The ``File`` object
===================
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.
.. _built-in file object: http://docs.python.org/library/stdtypes.html#bltin-file-objects
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
:doc:`/ref/files/file`.
File storage
============
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 :setting:`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
:doc:`/howto/custom-file-storage` for information on writing your own file
storage system.
Storage objects
---------------
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 :doc:`/ref/files/storage` for the file storage API.
The built-in filesystem storage class
-------------------------------------
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)
:doc:`Custom storage systems </howto/custom-file-storage>` work the same way: you
can pass them in as the ``storage`` argument to a ``FileField``.
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