How To Construct An In-memory Virtual File System And Then Write This Structure To Disk

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 con

Solution 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)

Solution 2:

If you just want to stage a file system tree in memory, look at the (tarfile module)[https://docs.python.org/3/library/tarfile.html].

Creating files and directories is a bit involved:

tarblob = io.BytesIO()
tar = tarfile.TarFile(mode="w", fileobj=tarblob)
dirinfo = tarfile.TarInfo("directory")
dirinfo.mode = 0o755
dirinfo.type = tarfile.DIRTYPE
tar.addfile(dirinfo, None)

filedata = io.BytesIO(b"Hello, world!\n")
fileinfo = tarfile.TarInfo("directory/file")
fileinfo.size = len(filedata.getbuffer())
tar.addfile(fileinfo, filedata)
tar.close()

But then you can create the file system hierarchy using TarFile.extractall:

tarblob.seek(0) # Rewind to the beginning of the buffer.
tar = tarfile.TarFile(mode="r", fileobj=tarblob)
tar.extractall()