libtmux::Window::select

>>> window = session.active_window
>>> new_window = session.new_window()
>>> session.refresh()
>>> active_windows = [w for w in session.windows if w.window_active == '1']

>>> new_window.window_active == '1'
False

>>> new_window.select()
Window(...)

>>> new_window.window_active == '1'
True

await window.select();