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146 lines
5.2 KiB
Plaintext
146 lines
5.2 KiB
Plaintext
==============
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Managing files
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==============
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This document describes Django's file access APIs.
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By default, Django stores files locally, using the :setting:`MEDIA_ROOT` and
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:setting:`MEDIA_URL` settings. The examples below assume that you're using these
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defaults.
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However, Django provides ways to write custom `file storage systems`_ that
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allow you to completely customize where and how Django stores files. The
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second half of this document describes how these storage systems work.
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.. _file storage systems: `File storage`_
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Using files in models
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=====================
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When you use a :class:`~django.db.models.FileField` or
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:class:`~django.db.models.ImageField`, Django provides a set of APIs you can use
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to deal with that file.
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Consider the following model, using an :class:`~django.db.models.ImageField` to
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store a photo::
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class Car(models.Model):
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name = models.CharField(max_length=255)
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price = models.DecimalField(max_digits=5, decimal_places=2)
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photo = models.ImageField(upload_to='cars')
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Any ``Car`` instance will have a ``photo`` attribute that you can use to get at
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the details of the attached photo::
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>>> car = Car.objects.get(name="57 Chevy")
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>>> car.photo
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<ImageFieldFile: chevy.jpg>
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>>> car.photo.name
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u'cars/chevy.jpg'
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>>> car.photo.path
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u'/media/cars/chevy.jpg'
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>>> car.photo.url
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u'http://media.example.com/cars/chevy.jpg'
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This object -- ``car.photo`` in the example -- is a ``File`` object, which means
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it has all the methods and attributes described below.
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The ``File`` object
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===================
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Internally, Django uses a :class:`django.core.files.File` instance any time it
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needs to represent a file. This object is a thin wrapper around Python's
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`built-in file object`_ with some Django-specific additions.
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.. _built-in file object: http://docs.python.org/library/stdtypes.html#bltin-file-objects
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Most of the time you'll simply use a ``File`` that Django's given you (i.e. a
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file attached to a model as above, or perhaps an uploaded file).
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If you need to construct a ``File`` yourself, the easiest way is to create one
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using a Python built-in ``file`` object::
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>>> from django.core.files import File
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# Create a Python file object using open()
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>>> f = open('/tmp/hello.world', 'w')
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>>> myfile = File(f)
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Now you can use any of the documented attributes and methods
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of the :class:`~django.core.files.File` class.
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File storage
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============
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Behind the scenes, Django delegates decisions about how and where to store files
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to a file storage system. This is the object that actually understands things
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like file systems, opening and reading files, etc.
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Django's default file storage is given by the :setting:`DEFAULT_FILE_STORAGE`
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setting; if you don't explicitly provide a storage system, this is the one that
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will be used.
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See below for details of the built-in default file storage system, and see
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:doc:`/howto/custom-file-storage` for information on writing your own file
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storage system.
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Storage objects
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---------------
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Though most of the time you'll want to use a ``File`` object (which delegates to
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the proper storage for that file), you can use file storage systems directly.
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You can create an instance of some custom file storage class, or -- often more
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useful -- you can use the global default storage system::
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>>> from django.core.files.storage import default_storage
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>>> from django.core.files.base import ContentFile
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>>> path = default_storage.save('/path/to/file', ContentFile('new content'))
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>>> path
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u'/path/to/file'
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>>> default_storage.size(path)
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11
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>>> default_storage.open(path).read()
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'new content'
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>>> default_storage.delete(path)
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>>> default_storage.exists(path)
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False
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See :doc:`/ref/files/storage` for the file storage API.
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The built-in filesystem storage class
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-------------------------------------
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Django ships with a built-in ``FileSystemStorage`` class (defined in
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``django.core.files.storage``) which implements basic local filesystem file
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storage. Its initializer takes two arguments:
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====================== ===================================================
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Argument Description
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====================== ===================================================
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``location`` Optional. Absolute path to the directory that will
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hold the files. If omitted, it will be set to the
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value of your :setting:`MEDIA_ROOT` setting.
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``base_url`` Optional. URL that serves the files stored at this
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location. If omitted, it will default to the value
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of your :setting:`MEDIA_URL` setting.
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====================== ===================================================
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For example, the following code will store uploaded files under
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``/media/photos`` regardless of what your :setting:`MEDIA_ROOT` setting is::
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from django.db import models
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from django.core.files.storage import FileSystemStorage
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fs = FileSystemStorage(location='/media/photos')
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class Car(models.Model):
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...
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photo = models.ImageField(storage=fs)
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:doc:`Custom storage systems </howto/custom-file-storage>` work the same way:
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you can pass them in as the ``storage`` argument to a
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:class:`~django.db.models.FileField`.
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