File オブジェクト

django.core.files モジュールとそのサブモジュールでは、Django の基本的なファイルハンドリングに関するビルトインクラスが定義されています。

File クラス

class File(file_object)[ソース]

File クラスは、Python の file object に Django 特有の追加機能を付け加えた薄いラッパーです。内部的でファイルを表現する必要がある場合には、Django はこのクラスを使います。

File オブジェクトには次の属性とメソッドを持ちます。

name

MEDIA_ROOT からの相対パスを含むファイル名です。

size

bytes で表されたファイルサイズ。

file

このクラスがラッピングしている、素の file object クラスです。

この属性をサブクラスで扱う場合には注意が必要です。

ContentFileFieldFile など File のサブクラスは、この属性を Python の file object 以外のオブジェクトに置き換えることがあります。このような場合には、この属性自体は File のサブクラスであるかもしれません (が、同じサブクラスとは限りません)。そのため、可能な限り、サブクラスの file 属性ではなく、サブクラス自身が持つ属性やメソッドを使用するようにしてください。

mode

ファイルの読み込み/書き込みのモードです。

open(mode=None)[ソース]

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:.

Changed in Django 2.0:

Context manager support was added.

__iter__()[ソース]

Iterate over the file yielding one line at a time.

chunks(chunk_size=None)[ソース]

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)[ソース]

Returns True if the file is large enough to require multiple chunks to access all of its content give some chunk_size.

close()[ソース]

Close the file.

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().

Changed in Django 1.11:

The readable() and writable() methods were added.

The ContentFile class

class ContentFile(File)[ソース]

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 sentencia está en español")
f2 = ContentFile(b"these are bytes")

The ImageFile class

class ImageFile(file_object)[ソース]

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

Width of the image in pixels.

height

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()

are equivalent to:

>>> 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.

File.delete(save=True)

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.

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