This is a continuation of my previous article: Save Snippets of Python code as single XML file

Creating a Virtual File System with FUSE and Python

FUSE (Filesystem in Userspace) is a software interface that allows user-level programs to create and manage file systems without requiring root privileges. This makes it possible to create custom file systems that can be mounted and accessed like regular file systems.

In this article, we will create a virtual file system using FUSE and Python. The file system will expose a set of Python code snippets as files, allowing users to read and execute the snippets as if they were regular Python scripts.

Installing FUSE and the Python bindings

Before we can use FUSE in Python, we need to install the FUSE library and the Python bindings. On Ubuntu and other Debian-based systems, you can install the required packages using the following command:

sudo apt-get install fuse libfuse-dev python3-fuse

On other systems, you may need to use a different package manager or install the packages from source.

Writing the code

Our virtual file system will be based on an XML file that contains a set of named Python code snippets. We will use the xml.etree.ElementTree module to parse the XML file and create a dictionary of snippets. We will then use the fusepy library to create a FUSE file system that exposes the snippets as files.

Here’s the code:

import xml.etree.ElementTree as ET
import os
import errno
import argparse
from fuse import FUSE, FuseOSError, Operations

# Define a class that implements the FUSE operations
class SnippetFS(Operations):
    def __init__(self, xml_path):
        # Parse the XML file and create a dictionary of snippets
        self.snippets = {}
        tree = ET.parse(xml_path)
        root = tree.getroot()
        for snippet in root.findall('snippet'):
            name = snippet.find('name').text
            code = snippet.find('code').text.strip()
            self.snippets[name] = code
    
    def getattr(self, path, fh=None):
        # Treat all snippets as regular files with 444 permissions
        st = {}
        st['st_mode'] = 0o100444
        st['st_size'] = 0
        return st
    
    def read(self, path, size, offset, fh):
        # Get the code for the requested snippet and return the appropriate slice
        name = os.path.basename(path)
        if name not in self.snippets:
            raise FuseOSError(errno.ENOENT)
        code = self.snippets[name]
        return code.encode()[offset:offset+size]
    
    def readdir(self, path, fh):
        # List all snippet names in the root directory
        return ['.', '..', *self.snippets.keys()]

# Parse command line arguments
parser = argparse.ArgumentParser()
parser.add_argument('xml_path', help='Path to the XML file')
parser.add_argument('mount_point', help='Mount point for the virtual file system')
args = parser.parse_args()

# Mount the SnippetFS filesystem at the specified mount point
os.makedirs(args.mount_point, exist_ok=True)
FUSE(SnippetFS(args.xml_path), args.mount_point, nothreads=True, foreground=True)

This code defines a SnippetFS class that implements the FUSE operations, and a main function that creates a virtual file system using the specified XML file and mount point. The SnippetFS class parses the XML file and creates a dictionary of named code snippets. The getattr, read, and readdir methods of the class implement the required FUSE operations.

Running the program

To run the program, save the code to a file called snippetfs.py and create an XML file with the following format:

<python_snippets>
  <snippet>
    <name>Snippet 1</name>
    <code><![CDATA[
      # Python code for Snippet 1
      print("Hello, world!")
    ]]></code>
  </snippet>
  <snippet>
    <name>Snippet 2</name>
    <code><![CDATA[
      # Python code for Snippet 2
      x = 10
      y = 20
      print(x + y)
    ]]></code>
  </snippet>
  <snippet>
    <name>Snippet 3</name>
    <code><![CDATA[
      # Python code for Snippet 3
      def greet(name):
        print("Hello, " + name + "!")
        
      greet("Alice")
    ]]></code>
  </snippet>
</python_snippets>

Replace the contents of the XML file with your own Python snippets as desired.

To mount the virtual file system, use the following command:

python3 snippetfs.py path/to/xml/file /path/to/mount/point

Replace path/to/xml/file with the path to your XML file and /path/to/mount/point with the path to the directory where you want to mount the file system.

Once the file system is mounted, you can browse the snippets like regular files and execute them by running python3 /path/to/mount/point/Snippet\ X (where X is the name of the snippet).

Conclusion

In this article, we have demonstrated how to create a virtual file system using FUSE and Python. The file system exposes a set of Python code snippets as files, allowing users to read and execute the snippets like regular Python scripts. This technique can be used to create other types of virtual file systems, such as file systems that expose data from databases or web services.

Happy coding!