django1/docs/ref/files/file.txt

The ``File`` object
===================

.. currentmodule:: django.core.files

``File`` attributes and methods
-------------------------------

The :mod:`django.core.files` module contains a built-in class for basic file
handling in Django. The :class:`File` class has the following attributes and
methods:

.. class:: File(file_object)

    .. attribute:: name

        The name of file including the relative path from :setting:`MEDIA_ROOT`.

    .. attribute:: path

        The absolute path to the file's location on a local filesystem.

        :doc:`Custom file storage systems </howto/custom-file-storage>` may not store
        files locally; files stored on these systems will have a ``path`` of
        ``None``.

    .. attribute:: url

        The URL where the file can be retrieved. This is often useful in
        :doc:`templates </topics/templates>`; for example, a bit of a template for
        displaying a ``Car`` (see above) might look like:
        
        .. code-block:: html+django

            <img src='{{ car.photo.url }}' alt='{{ car.name }}' />

    .. attribute:: size

        The size of the file in bytes.

    .. method:: open([mode=None])

        Open or reopen the file (which by definition also does ``File.seek(0)``).
        The ``mode`` argument allows the same values as Python's standard
        ``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
        ``close()`` is called on the file.

    .. method:: close()

        Close the file.

.. currentmodule:: django.core.files.images

Additional ``ImageField`` attributes
------------------------------------

.. class:: ImageFile(file_object)

    .. attribute:: width
        
        Width of the image.

    .. attribute:: height

        Height of the image.

.. currentmodule:: django.core.files

Additional methods on files attached to objects
-----------------------------------------------

Any :class:`File` that's associated with an object (as with ``Car.photo``,
above) 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', contents, save=False)
        >>> car.save()
    
    are the same as this one line::
    
        >>> car.photo.save('myphoto.jpg', contents, save=True)
    
    Note that the ``content`` argument must be an instance of
    :class:`File` or of a subclass of :class:`File`.

.. method:: File.delete([save=True])

    Remove the file from the model instance and delete the underlying file. The
    ``save`` argument works as above.