# Django 2.2.9.dev20191202104323 文档

# `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)

  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)

    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__`()

    Iterate over the file yielding one line at a time.

  `chunks`(chunk_size=None)

    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`.

  `close`()

    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)

  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)

  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.