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The ``File`` object
===================
The :mod:`django.core.files` module and its submodules contain built-in classes
for basic file handling in Django.
.. currentmodule:: django.core.files
The ``File`` Class
------------------
.. class:: File(file_object)
The :class:`File` class is a thin wrapper around a Python
:py:term:`file object` with some Django-specific additions.
Internally, Django uses this class when it needs to represent a file.
:class:`File` objects have the following attributes and methods:
.. attribute:: name
The name of the file including the relative path from
:setting:`MEDIA_ROOT`.
.. attribute:: size
The size of the file in bytes.
.. attribute:: file
The underlying :py:term:`file object` that this class wraps.
.. attribute:: mode
The read/write mode for the file.
.. method:: 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 :func:`python:open()`.
When reopening a file, ``mode`` will override whatever mode the file
was originally opened with; ``None`` means to reopen with the original
mode.
.. method:: read(num_bytes=None)
Read content from the file. The optional ``size`` is the number of
bytes to read; if not specified, the file will be read to the end.
.. method:: __iter__()
Iterate over the file yielding one line at a time.
.. method:: 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.
.. method:: 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``.
.. method:: write(content)
Writes the specified content string to the file. Depending on the
storage system behind the scenes, this content might not be fully
committed until :func:`close()` is called on the file.
.. method:: close()
Close the file.
In addition to the listed methods, :class:`~django.core.files.File` exposes
the following attributes and methods of its ``file`` object:
``encoding``, ``fileno``, ``flush``, ``isatty``, ``newlines``,
``read``, ``readinto``, ``readlines``, ``seek``, ``softspace``, ``tell``,
``truncate``, ``writelines``, ``xreadlines``. If you are using
Python 3, the ``seekable`` method is also available.
.. versionchanged:: 1.9
The ``seekable`` method was added.
.. currentmodule:: django.core.files.base
The ``ContentFile`` Class
-------------------------
.. class:: ContentFile(File)
The ``ContentFile`` class inherits from :class:`~django.core.files.File`,
but unlike :class:`~django.core.files.File` it operates on string content
(bytes also supported), rather than an actual file. For example::
from __future__ import unicode_literals
from django.core.files.base import ContentFile
f1 = ContentFile("esta sentencia está en español")
f2 = ContentFile(b"these are bytes")
.. currentmodule:: django.core.files.images
The ``ImageFile`` Class
-----------------------
.. class:: ImageFile(file_object)
Django provides a built-in class specifically for images.
:class:`django.core.files.images.ImageFile` inherits all the attributes
and methods of :class:`~django.core.files.File`, and additionally
provides the following:
.. attribute:: width
Width of the image in pixels.
.. attribute:: height
Height of the image in pixels.
.. currentmodule:: django.core.files
Additional methods on files attached to objects
-----------------------------------------------
Any :class:`File` that is associated with an object (as with ``Car.photo``,
below) will also have a couple of extra methods:
.. method:: 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
:class:`File` or of a subclass of :class:`File`, such as
:class:`~django.core.files.base.ContentFile`.
.. method:: 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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