django/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(location=None, base_url=None, file_permissions_mode=None, directory_permissions_mode=None)

    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.

    .. attribute:: location

        Absolute path to the directory that will hold the files.
        Defaults to the value of your :setting:`MEDIA_ROOT` setting.

    .. attribute:: base_url

        URL that serves the files stored at this location.
        Defaults to the value of your :setting:`MEDIA_URL` setting.

    .. attribute:: file_permissions_mode

        The file system permissions that the file will receive when it is
        saved. Defaults to :setting:`FILE_UPLOAD_PERMISSIONS`.

    .. attribute:: directory_permissions_mode

        The file system permissions that the directory will receive when it is
        saved. Defaults to :setting:`FILE_UPLOAD_DIRECTORY_PERMISSIONS`.

    .. note::

        The ``FileSystemStorage.delete()`` method will not raise
        an exception if the given file name does not exist.

    .. method:: get_created_time(name)

        Returns a :class:`~datetime.datetime` of the system's ctime, i.e.
        :func:`os.path.getctime`. On some systems (like Unix), this is the
        time of the last metadata change, and on others (like Windows), it's
        the creation time of the file.

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.

    .. note::
        When methods return naive ``datetime`` objects, the effective timezone
        used will be the current value of ``os.environ['TZ']``; note that this
        is usually set from Django's :setting:`TIME_ZONE`.

    .. method:: delete(name)

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

    .. method:: exists(name)

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

    .. method:: get_accessed_time(name)

        Returns a :class:`~datetime.datetime` of the last accessed time of the
        file. For storage systems unable to return the last accessed time this
        will raise :exc:`NotImplementedError`.

        If :setting:`USE_TZ` is ``True``, returns an aware ``datetime``,
        otherwise returns a naive ``datetime`` in the local timezone.

    .. method:: get_alternative_name(file_root, file_ext)

        Returns an alternative filename based on the ``file_root`` and
        ``file_ext`` parameters, an underscore plus a random 7 character
        alphanumeric string is appended to the filename before the extension.

    .. method:: get_available_name(name, max_length=None)

        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.

        The length of the filename will not exceed ``max_length``, if provided.
        If a free unique filename cannot be found, a
        :exc:`SuspiciousFileOperation
        <django.core.exceptions.SuspiciousOperation>` exception will be raised.

        If a file with ``name`` already exists, :meth:`get_alternative_name` is
        called to obtain an alternative name.

    .. method:: get_created_time(name)

        Returns a :class:`~datetime.datetime` of the creation time of the file.
        For storage systems unable to return the creation time this will raise
        :exc:`NotImplementedError`.

        If :setting:`USE_TZ` is ``True``, returns an aware ``datetime``,
        otherwise returns a naive ``datetime`` in the local timezone.

    .. method:: get_modified_time(name)

        Returns a :class:`~datetime.datetime` of the last modified time of the
        file. For storage systems unable to return the last modified time this
        will raise :exc:`NotImplementedError`.

        If :setting:`USE_TZ` is ``True``, returns an aware ``datetime``,
        otherwise returns a naive ``datetime`` in the local timezone.

    .. method:: get_valid_name(name)

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

    .. method:: generate_filename(filename)

        Validates the ``filename`` by calling :attr:`get_valid_name()` and
        returns a filename to be passed to the :meth:`save` method.

        The ``filename`` argument may include a path as returned by
        :attr:`FileField.upload_to <django.db.models.FileField.upload_to>`.
        In that case, the path won't be passed to :attr:`get_valid_name()` but
        will be prepended back to the resulting name.

        The default implementation uses :mod:`os.path` operations. Override
        this method if that's not appropriate for your storage.

    .. 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, max_length=None)

        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 ``max_length`` argument is passed along to
        :meth:`get_available_name`.

        The ``content`` argument must be an instance of
        :class:`django.core.files.File` or a file-like object that can be
        wrapped in ``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.