pathlib_abc_custom_readonly_path_subclass_with_dict_backend.py

1import stat
2from pathlib_abc import PathBase
3
4class MyPath(PathBase):
5    """
6    A simple read-only path implementation that serves files from a dict.
7    """
8    _files = {
9        '/': (stat.S_IFDIR | 0o755, None),
10        '/etc': (stat.S_IFDIR | 0o755, None),
11        '/etc/passwd': (stat.S_IFREG | 0o644, b'root:x:0:0:root:/root:/bin/bash'),
12    }
13
14    def _stat(self):
15        try:
16            mode, data = self._files[str(self)]
17        except KeyError:
18            raise FileNotFoundError(self)
19        return stat.struct_stat((mode, 0, 0, 0, 0, 0, len(data or b''), 0, 0, 0))
20
21    def _readdir(self):
22        parent = str(self)
23        for path in self._files:
24            if path != parent and path.startswith(parent):
25                rel = path[len(parent):].lstrip('/')
26                if '/' not in rel:
27                    yield rel
28
29    def open(self, mode='r', buffering=-1, encoding=None, errors=None, newline=None):
30        if mode not in ('r', 'rb'):
31            raise PermissionError("Read-only file system")
32        try:
33            mode_bits, data = self._files[str(self)]
34        except KeyError:
35            raise FileNotFoundError(self)
36        if stat.S_ISDIR(mode_bits):
37            raise IsADirectoryError(self)
38        
39        import io
40        stream = io.BytesIO(data)
41        if 'b' not in mode:
42            stream = io.TextIOWrapper(stream, encoding, errors, newline)
43        return stream
44
45# Usage example:
46path = MyPath('/etc/passwd')
47print(f"Path: {path}")
48print(f"Content: {path.read_text()}")
49print(f"Exists: {path.exists()}")