A Mount FS is a virtual filesystem which can seamlessly map sub-directories on to other filesystems.

For example, lets say we have two filesystems containing config files and resources respectively:

   |-- config.cfg
   `-- defaults.cfg

   |-- images
   |   |-- logo.jpg
   |   `-- photo.jpg
   `-- data.dat

We can combine these filesystems in to a single filesystem with the following code:

from fs.mountfs import MountFS
combined_fs = MountFS()
combined_fs.mount('config', config_fs)
combined_fs.mount('resources', resources_fs)

This will create a filesystem where paths under config/ map to config_fs, and paths under resources/ map to resources_fs:

    |-- config
    |   |-- config.cfg
    |   `-- defaults.cfg
    `-- resources
        |-- images
        |   |-- logo.jpg
        |   `-- photo.jpg
        `-- data.dat

Now both filesystems may be accessed with the same path structure:

with'/resources/images/logo.jpg', 'rb') as image_file:
    img = read_jpg(image_file)

See the MountFS docs for more information.

Will McGugan
Aug 15, 2017