how-to-open.md

How to redirect file access

Use the open hook when code calls builtins.open and needs a filesystem-backed root. Install the backend required by the URL first.

from fsspec_python import install_open_hook, uninstall_open_hook

install_open_hook("memory://open-demo")
try:
    with open("result.txt", "w") as output:
        output.write("complete\n")
    with open("result.txt") as source:
        print(source.read().strip())
finally:
    uninstall_open_hook()

The output is complete. Replace the memory URL with your target root, and pass backend storage options as keyword arguments to install_open_hook.

Keep the hook's lifetime short and restore it in finally. It changes builtins.open for the whole process. Missing read paths fall back to the original local open; write, append, and exclusive-create paths use the configured backend.

See API reference for argument handling and unsupported hooks.