File 对象

The django.core.files module and its submodules contain built-in classes for basic file handling in Django.

The File class

class File(file_object)[源代码]

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:

• name

  The name of the file including the relative path from MEDIA_ROOT.

• size

  The size of the file in bytes.

• file

  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.

• mode

  The read/write mode for the file.

• open(mode=None)[源代码]

  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:.

• __iter__()[源代码]

  Iterate over the file yielding one line at a time.

• chunks(chunk_size=None)[源代码]

  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)[源代码]

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

• close()[源代码]

  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().

The ContentFile class

class ContentFile(File)[源代码]

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

class ImageFile(file_object)[源代码]

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.