TopolearnTools that build remote paths (S3 keys, SSH targets, Windows shares from Linux) need the other OS's rules.
pathlib has two families of classes:
- Pure paths (
PurePath,PurePosixPath,PureWindowsPath) do only string operations: joining, parts, suffixes, matching. They never touch the file system, so they work for any platform's paths on any platform. - Concrete paths (
Path,PosixPath,WindowsPath) add I/O methods. You can only instantiate the concrete class of your own OS;WindowsPathon Linux raisesUnsupportedOperation(3.13).
Use pure paths when the path isn't on the local machine:
PurePosixPath("bucket") / "2025" / "a.csv"for object-store keys or paths on a remote Linux server, even when your code runs on Windows.PureWindowsPath(r"C:\Users\ann\file.txt")to parse Windows paths received in data on a Linux server.
Windows rules differ: both \ and / are separators, drives and UNC shares form the anchor (C:\, \\server\share\), comparison is case-insensitive, and p.as_posix() converts to forward slashes.
p.as_uri() turns an absolute path into a file:// URL, and since 3.13 Path.from_uri() parses one back.
Note that pure paths accept any string; they won't tell you a name is invalid on Windows (such as CON or one containing :).
Example
from pathlib import Path, PurePosixPath, PureWindowsPath
w = PureWindowsPath(r"C:\Users\Ann\Docs/report.DOCX")
print(w.parts) # ('C:\\', 'Users', 'Ann', 'Docs', 'report.DOCX')
print(w.drive, w.suffix) # C: .DOCX
print(w.as_posix()) # C:/Users/Ann/Docs/report.DOCX
print(w == PureWindowsPath(r"c:\users\ann\docs\REPORT.docx")) # True
key = PurePosixPath("exports") / "2025" / "sales.csv" # e.g. an S3 key
print(str(key)) # exports/2025/sales.csv
uri = Path("/tmp/a b.txt").as_uri()
print(uri) # file:///tmp/a%20b.txt
print(Path.from_uri(uri)) # /tmp/a b.txtRemember
- Pure paths do string-only path logic for any OS; concrete paths add I/O
- Use PurePosixPath for remote or object-store paths regardless of the local OS
- Windows paths compare case-insensitively and accept both slash styles
Watch out for
- Using
Path(and so local separators) to build S3 keys or remote Linux paths when code may run on Windows.