clipboard-event

clipboard-event provides clipboard text access and change callbacks for Python on Windows and macOS. It uses native change notifications where available and has no runtime dependencies.

• Windows: reads and writes Unicode text through Win32 and listens for WM_CLIPBOARDUPDATE on a message-only window.
• macOS: reads and writes through pbpaste and pbcopy, then observes NSPasteboard.changeCount without polling clipboard content continuously.
• If native monitoring cannot start on a supported platform, the library falls back to polling. Other platforms fail explicitly.

Installation

Once the package is published on PyPI:

pip install clipboard-event

The project requires Python 3.10 or newer.

Quick start

The module facade creates its default clipboard instance only when first used:

import clipboard_event

print(clipboard_event.read())
clipboard_event.write("Hello from Python")

subscription = clipboard_event.on_change(
    lambda value: print(f"Clipboard changed: {value!r}"),
    emit_initial=True,
)

# Later:
subscription.cancel()
clipboard_event.close()

Explicit instances

Use Clipboard when you need an independent lifecycle:

from clipboard_event import Clipboard, Subscription

clipboard = Clipboard()

def changed(value: str | None) -> None:
    print(value)

subscription: Subscription = clipboard.on_change(changed)
clipboard.write("This write also triggers the callback")

subscription.cancel()
clipboard.close()

Subscription.cancel() and Clipboard.close() are idempotent. Closing a Clipboard cancels its subscriptions and releases monitor threads and native watcher resources. read() and write() remain usable after close, and a later on_change() call starts monitoring again.

Callbacks run sequentially on one Python dispatcher thread, never on a native watcher thread. One callback's exception does not stop other subscriptions. Rapid changes may coalesce, so a callback can receive only the latest value. A callback receives str for text or None when no text is available. Writes made through the library are observed like external changes.

For diagnostics, inspect the selected backend:

print(clipboard.backend_name)  # "win32", "macos", or "polling"

Support

The package is pure Python. Its wheel is universal because platform integration happens at runtime through the standard library and system tools; no compiled extension is included.

Development

Create and activate a virtual environment, then install the project in editable mode:

python -m pip install -e .
python -m unittest discover -s tests -t .
python tests/native_smoke.py

Build and inspect distribution artifacts with:

python -m pip install build twine
python -m build
python -m twine check dist/*

License

MIT © 2026 Jordi Murgó.