How to construct an in-memory virtual file system and then write this structure to disk

Question

I'm looking for a way to create a virtual file system in Python for creating directories and files, before writing these directories and files to disk.

Using PyFilesystem I can construct a memory filesystem using the following:

>>> import fs
>>> dir = fs.open_fs('mem://')
>>> dir.makedirs('fruit')
SubFS(MemoryFS(), '/fruit')
>>> dir.makedirs('vegetables')
SubFS(MemoryFS(), '/vegetables')
>>> with dir.open('fruit/apple.txt', 'w') as apple: apple.write('braeburn')
... 
8
>>> dir.tree()
├── fruit
│   └── apple.txt
└── vegetables

Ideally, I want to be able to do something like:

dir.write_to_disk('<base path>')

To write this structure to disk, where <base path> is the parent directory in which this structure will be created.

As far as I can tell, PyFilesystem has no way of achieving this. Is there anything else I could use instead or would I have to implement this myself?

Answer 1

You can use fs.copy.copy_fs() to copy from one filesystem to another, or fs.move.move_fs() to move the filesystem altogether.

Given that PyFilesystem also abstracts around the underlying system filesystem - OSFS - in fact, it's the default protocol, all you need is to copy your in-memory filesystem (MemoryFS) to it and, in effect, you'll have it written to the disk:

import fs
import fs.copy

mem_fs = fs.open_fs('mem://')
mem_fs.makedirs('fruit')
mem_fs.makedirs('vegetables')
with mem_fs.open('fruit/apple.txt', 'w') as apple:
    apple.write('braeburn')

# write to the CWD for testing...
with fs.open_fs(".") as os_fs:  # use a custom path if you want, i.e. osfs://<base_path>
    fs.copy.copy_fs(mem_fs, os_fs)