管理文件

这个文档描述 Django 文件访问用于文件的 API，例如用户上传的文件。较底层的API足够通用，你可以为其他目的来使用它们。如果你想处理 “static files” (JS, CSS, etc.)，可以查看 如何管理静态文件（如图片、JavaScript、CSS） 。

默认情况下，Django 使用 MEDIA_ROOT 和 MEDIA_URL 设置本地存储。下面的例子假设你在使用这些默认设置。

不过，Django 提供编写自定义 file storage systems 的方法，允许你完全自定义 Django 存储文件的位置和方式。这篇文档的后半部分描述了存储系统的工作方式。

在模型中使用文件

当你使用 FileField 或 ImageField 时，Django 提供了一组处理文件的API。

考虑下面的模型，使用 ImageField 来存储照片：

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
<ImageFieldFile: cars/chevy.jpg>
>>> car.photo.name
'cars/chevy.jpg'
>>> car.photo.path
'/media/cars/chevy.jpg'
>>> car.photo.url
'http://media.example.com/cars/chevy.jpg'

car.photo 是一个 File 对象，这意味着它拥有下面所描述的所有方法和属性。

备注

文件在数据库中作为保存模型的一部分，因此在模型被保存之前，不能依赖磁盘上使用的实际文件名。

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()
...

备注

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()
<ImageFieldFile: cars/chevy.jpg>
>>> image = Image.open(car.photo)
>>> image
<PIL.JpegImagePlugin.JpegImageFile image mode=RGB size=191x287 at 0x7F99A94E9048>

File 对象

在内部，Django 在任何需要表示文件的时候使用 django.core.files.File 。

大部分情况下你只需要使用 Django 提供的 File （即附加到上述模型的文件或已经上传的文件）。

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)

现在你可以使用 File 类的任何属性和方法。

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

文件存储

在后台，Django将如何以及在哪里存储文件的决策委托给文件存储系统。这个对象实际上理解文件系统、打开和读取文件等。

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.

参阅下面内置默认文件存储系统的细节，也可以查看 如何编写一个自定义的文件存储类 来了解编写自己的文件存储系统的信息。

存储对象

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

查看 文件存储 API 来了解文件存储API。

内置文件存储类

Django 附带一个 django.core.files.storage.FileSystemStorage 类，这个类实现基础的本地文件系统文件存储。

例如，下面的代码将存储上传文件到 /media/photos 而会忽略你在 MEDIA_ROOT 的设置：

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)

自定义存储系统（ Custom storage systems ）的工作方式也一样：将它们作为 storage 参数传递给 FileField 。

使用callable

你可以使用callable作为 FileField 或 ImageField 的 storage 参数。它允许你在运行时修改存储参数，不同环境选择不同存储，例如。

当模型类被加载时，callable将进行判断，并返回 Storage 实例。

例如：

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)

Changed in Django 4.2:

Support for storages was added.