A MemoryFS is a filesystem that exists entirely in memory.
Since a memory filesystems isn't backed by any persistant storage, it is very fast. The downside is, of course, that when you a close a memory filesystem, the files and folders disappear.
Here's how you can create a memory filesystem:
from fs.memoryfs import MemoryFS mem_fs = MemoryFS()
Or by using an FS url:
from fs import open_fs mem_fs = open_fs('mem://')
A memory-based filesystem is surprisingly useful, with use-cases similar to TempFS ; including caching and unit tests.
See MemoryFS docs for more information.