MultiFS

A MultiFS is a filesystem composed of a sequence of other filesystems, where the directory structure of each overlays the previous filesystem in the sequence.

One use for such a filesystem would be to selectively override a set of files, to customize behavior. For example, to create a filesystem that could be used to theme a web application. We start with the following directories:

`-- templates
    |-- snippets
    |   `-- panel.html
    |-- index.html
    |-- profile.html
    `-- base.html

`-- theme
    |-- snippets
    |   |-- widget.html
    |   `-- extra.html
    |-- index.html
    `-- theme.html

And we want to create a single filesystem that will load a file from templates/ only if it isn't found in theme/. Here's how we could do that:

from fs.osfs import OSFS
from fs.multifs import MultiFS

theme_fs = MultiFS()
theme_fs.add_fs('templates', OSFS('templates'))
theme_fs.add_fs('theme', OSFS('theme'))

Now we have a theme_fs filesystem that presents a single view of both directories::

[theme_fs]
|-- snippets
|   |-- panel.html
|   |-- widget.html
|   `-- extra.html
|-- index.html
|-- profile.html
|-- base.html
`-- theme.html

See the MultiFS Docs for more information.

See MountFS for another similar virtual filesystem.