Virtual file system — Python: Trees

In this course, we'll create a virtual file system and implement everyday operations for working with it, such as counting free space, searching for files and directories, etc. It is what the creation of this tree looks like:

from hexlet import fs

tree = fs.mkdir('etc', [
    fs.mkfile('bashrc'),
    fs.mkdir('consul', [
        fs.mkfile('config.json'),
    ]),
])

The mkdir here takes a list of children as the second parameter that can either be directories created by mkdir or files created by mkfile. The result is this structure:

etc
├── bashrc
└── consul
    └── config.json

We can get any file structure by embedding mkdir and mkfile calls into other mkdirs. The root in this structure will be a directory, and the leaves may contain both files and empty directories. This structure is virtual, meaning we create zero files or directories. All the information about the file system is in the tree variable.

If you print it on the screen, we'll see the following contents:

{
  'name': 'etc',
  'type': 'directory',
  'meta': {},
  'children': [
    {
      'name': 'bashrc',
      'type': 'file',
      'meta': {},
    },
    {
      'name': 'consul',
      'type': 'directory',
      'meta': {},
      'children': [
        {
          'name': 'config.json',
          'type': 'file',
          'meta': {},
        }
      ],
    },
  ],
}

It is an internal implementation of the file tree. It consists of two types of nodes. The first one is directory representation:

{
  'name': 'dir_name',
  'type': 'directory',
  'children': [], # This is where we store children
  'meta': {} # Directory properties
}

The second one is file representation:

{
  'name': 'file_name',
  'type': 'file',
  'meta': {}, # File properties
}

Files and directories have names. It is the main thing they have in common. The type property determines the type of node. We can use it while we process the tree to understand what is in front of us. The meta is a dictionary with whatever data you need, for example, size or date of creation.

We set properties during node creation:

mkfile('.bashrc', {'size': 75})
mkdir('hexlet', [], {'owner': 'nobody'})

Metadata will be needed by functions that analyze the tree to, for example, calculate available space.

Recommended materials

1. The python-immutable-fs-trees library