lib/django-1.2/docs/ref/files/storage.txt

File storage API
================

.. module:: django.core.files.storage

Getting the current storage class
---------------------------------

Django provides two convenient ways to access the current storage class:

.. class:: DefaultStorage

    :class:`~django.core.files.storage.DefaultStorage` provides
    lazy access to the current default storage system as defined by
    :setting:`DEFAULT_FILE_STORAGE`. :class:`DefaultStorage` uses
    :func:`~django.core.files.storage.get_storage_class` internally.

.. function:: get_storage_class([import_path=None])

    Returns a class or module which implements the storage API.
    
    When called without the ``import_path`` parameter ``get_storage_class``
    will return the current default storage system as defined by
    :setting:`DEFAULT_FILE_STORAGE`. If ``import_path`` is provided,
    ``get_storage_class`` will attempt to import the class or module from the
    given path and will return it if successful. An exception will be
    raised if the import is unsuccessful.

The FileSystemStorage Class
---------------------------

.. class:: FileSystemStorage

    The :class:`~django.core.files.storage.FileSystemStorage` class implements
    basic file storage on a local filesystem. It inherits from
    :class:`~django.core.files.storage.Storage` and provides implementations
    for all the public methods thereof.
    
    .. note::
    
        The :class:`FileSystemStorage.delete` method will not raise
        raise an exception if the given file name does not exist.

The Storage Class
-----------------

.. class:: Storage

    The :class:`~django.core.files.storage.Storage` class provides a
    standardized API for storing files, along with a set of default
    behaviors that all other storage systems can inherit or override
    as necessary.

    .. method:: delete(name)

        Deletes the file referenced by ``name``. If deletion is not supported
        on the targest storage system this will raise ``NotImplementedError``
        instead

    .. method:: exists(name)

        Returns ``True`` if a file referened by the given name already exists
        in the storage system, or ``False`` if the name is available for a new
        file.

    .. method:: get_available_name(name)

        Returns a filename based on the ``name`` parameter that's free and
        available for new content to be written to on the target storage
        system.


    .. method:: get_valid_name(name)

        Returns a filename based on the ``name`` parameter that's suitable
        for use on the target storage system.

    .. method:: listdir(path)

        Lists the contents of the specified path, returning a 2-tuple of lists;
        the first item being directories, the second item being files. For
        storage systems that aren't able to provide such a listing, this will
        raise a ``NotImplementedError`` instead.

    .. method:: open(name, mode='rb')

        Opens the file given by ``name``. Note that although the returned file
        is guaranteed to be a ``File`` object, it might actually be some
        subclass. In the case of remote file storage this means that
        reading/writing could be quite slow, so be warned.

    .. method:: path(name)

        The local filesystem path where the file can be opened using Python's
        standard ``open()``. For storage systems that aren't accessible from
        the local filesystem, this will raise ``NotImplementedError`` instead.

    .. method:: save(name, content)

        Saves a new file using the storage system, preferably with the name
        specified. If there already exists a file with this name ``name``, the
        storage system may modify the filename as necessary to get a unique
        name. The actual name of the stored file will be returned.

        The ``content`` argument must be an instance of
        :class:`django.core.files.File` or of a subclass of
        :class:`~django.core.files.File`.

    .. method:: size(name)

        Returns the total size, in bytes, of the file referenced by ``name``.
        For storage systems that aren't able to return the file size this will
        raise ``NotImplementedError`` instead.

    .. method:: url(name)

        Returns the URL where the contents of the file referenced by ``name``
        can be accessed. For storage systems that don't support access by URL
        this will raise ``NotImplementedError`` instead.