IPython 5 startup file that makes the cursor wrap around lines when editing multiline input.

wrapping_cursor.py

def set_terminal_keybindings():
  
    """If IPython is running in the classic terminal mode, this function
    is called once, and is not called otherwise. We could have just used
    an if-block, but this way also keeps the variables local."""

    from prompt_toolkit.keys import Keys
    from prompt_toolkit.filters import Filter

    class StartOfLine(Filter):

        """Filter for checking whether the cursor is at the start of a
        line (other than the first line) in a multiline input."""

        def __call__(self, cli):

            document = cli.current_buffer.document
            offset = len(document.current_line_before_cursor)
            at_top = document.on_first_line
            return bool(offset == 0 and not at_top)

    class EndOfLine(Filter):

        """Filter for checking whether the cursor is at the end of a
        line (other than the last line) in a multiline input."""

        def __call__(self, cli):

            document = cli.current_buffer.document
            at_end = document.is_cursor_at_the_end_of_line
            at_bottom = document.is_cursor_at_the_end
            return bool(at_end and not at_bottom)

    def wrap_cursor_forwards(event):

        """Move the cursor to the start of the next line."""

        buff = event.cli.current_buffer
        relative_start_index = buff.document.get_start_of_line_position()
        buff.cursor_left(count=abs(relative_start_index))
        buff.cursor_down(count=1)

    def wrap_cursor_backwards(event):

        """Move the cursor to the end of the previous line."""

        buff = event.cli.current_buffer
        buff.cursor_up(count=1)
        relative_end_index = buff.document.get_end_of_line_position()
        buff.cursor_right(count=relative_end_index)

    bind_key = ip.pt_cli.application.key_bindings_registry.add_binding

    bind_key(Keys.Right, filter=EndOfLine())(wrap_cursor_forwards)
    bind_key(Keys.Left, filter=StartOfLine())(wrap_cursor_backwards)

ip = get_ipython()
if getattr(ip, "pt_cli"): set_terminal_keybindings()
del set_terminal_keybindings