The File object¶
The django.core.files module and its submodules contain built-in classes for basic file handling in Django.
The File class¶
The File class is a thin wrapper around a Python file object with some Django-specific additions. Internally, Django uses this class when it needs to represent a file.
File objects have the following attributes and methods:
The name of the file including the relative path from MEDIA_ROOT .
The size of the file in bytes.
The underlying file object that this class wraps.
Be careful with this attribute in subclasses.
Some subclasses of File , including ContentFile and FieldFile , may replace this attribute with an object other than a Python file object . In these cases, this attribute may itself be a File subclass (and not necessarily the same subclass). Whenever possible, use the attributes and methods of the subclass itself rather than the those of the subclass’s file attribute.
The read/write mode for the file.
Open or reopen the file (which also does File.seek(0) ). The mode argument allows the same values as Python’s built-in open() .
When reopening a file, mode will override whatever mode the file was originally opened with; None means to reopen with the original mode.
It can be used as a context manager, e.g. with file.open() as f: .
Iterate over the file yielding one line at a time.
Iterate over the file yielding “chunks” of a given size. chunk_size defaults to 64 KB.
This is especially useful with very large files since it allows them to be streamed off disk and avoids storing the whole file in memory.
multiple_chunks ( chunk_size = None )¶
Returns True if the file is large enough to require multiple chunks to access all of its content give some chunk_size .
In addition to the listed methods, File exposes the following attributes and methods of its file object: encoding , fileno , flush , isatty , newlines , read , readinto , readline , readlines , seek , tell , truncate , write , writelines , readable() , writable() , and seekable() .
The ContentFile class¶
The ContentFile class inherits from File , but unlike File it operates on string content (bytes also supported), rather than an actual file. For example:
from django.core.files.base import ContentFile f1 = ContentFile("esta frase está en español") f2 = ContentFile(b"these are bytes")
The ImageFile class¶
Django provides a built-in class specifically for images. django.core.files.images.ImageFile inherits all the attributes and methods of File , and additionally provides the following:
Width of the image in pixels.
Height of the image in pixels.
Additional methods on files attached to objects¶
Any File that is associated with an object (as with Car.photo , below) will also have a couple of extra methods:
File. save ( name , content , save = True )¶
Saves a new file with the file name and contents provided. This will not replace the existing file, but will create a new file and update the object to point to it. If save is True , the model’s save() method will be called once the file is saved. That is, these two lines:
>>> car.photo.save("myphoto.jpg", content, save=False) >>> car.save()
>>> car.photo.save("myphoto.jpg", content, save=True)
Note that the content argument must be an instance of either File or of a subclass of File , such as ContentFile .
Removes the file from the model instance and deletes the underlying file. If save is True , the model’s save() method will be called once the file is deleted.
Managing files¶
This document describes Django’s file access APIs for files such as those uploaded by a user. The lower level APIs are general enough that you could use them for other purposes. If you want to handle “static files” (JS, CSS, etc.), see How to manage static files (e.g. images, JavaScript, CSS) .
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.
Using files in models¶
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:
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") specs = models.FileField(upload_to="specs")
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 >>> 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.
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.
For example, you can change the file name by setting the file’s name to a path relative to the file storage’s location ( MEDIA_ROOT if you are using the default FileSystemStorage ):
>>> 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
To save an existing file on disk to a FileField :
>>> from pathlib import Path >>> from django.core.files import File >>> path = Path("/some/external/specs.pdf") >>> car = Car.objects.get(name="57 Chevy") >>> with path.open(mode="rb") as f: . car.specs = File(f, name=path.name) . car.save() .
While ImageField non-image data attributes, such as height , width , and size are 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() >>> image = Image.open(car.photo) >>> image
The File object¶
Internally, Django uses a django.core.files.File instance any time it needs to represent a file.
Most of the time you’ll 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("/path/to/hello.world", "w") >>> myfile = File(f)
Now you can use any of the documented attributes and methods of the File class.
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 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 ‘ django.core.files.storage.FileSystemStorage ‘ . If you don’t explicitly provide a storage system in the default key of the STORAGES setting, this is the one that will be used.
See below for details of the built-in default file storage system, and see How to write a custom storage class 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.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
See File storage API for the file storage API.
The built-in filesystem storage class¶
Django ships with a django.core.files.storage.FileSystemStorage class which implements basic local filesystem file storage.
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)
Custom storage systems work the same way: you can pass them in as the storage argument to a FileField .
Using a callable¶
You can use a callable as the storage parameter for FileField or ImageField . This allows you to modify the used storage at runtime, selecting different storages for different environments, for example.
Your callable will be evaluated when your models classes are loaded, and must return an instance of Storage .
from django.conf import settings from django.db import models from .storages import MyLocalStorage, MyRemoteStorage def select_storage(): return MyLocalStorage() if settings.DEBUG else MyRemoteStorage() class MyModel(models.Model): my_file = models.FileField(storage=select_storage)
In order to set a storage defined in the STORAGES setting you can use storages :
from django.core.files.storage import storages def select_storage(): return storages["mystorage"] class MyModel(models.Model): upload = models.FileField(storage=select_storage)
Support for storages was added.