Function pin_wait_change

pywebio/pin.py:326–365

``pin_wait_change()`` listens to a list of pin widgets, when the value of any widgets changes, the function returns with the name and value of the changed widget. :param str names: List of names of pin widget :param int/None timeout: If ``timeout`` is a positive number, ``pin_wait_chang

(*names, timeout: Optional[int] = None)

def pin_wait_change(*names, timeout: Optional[int] = None):
    """``pin_wait_change()`` listens to a list of pin widgets, when the value of any widgets changes,
    the function returns with the name and value of the changed widget.

    :param str names: List of names of pin widget
    :param int/None timeout: If ``timeout`` is a positive number, ``pin_wait_change()`` blocks at most ``timeout`` seconds
        and returns ``None`` if no changes to the widgets within that time. Set to ``None`` (the default) to disable timeout.
    :return dict/None: ``{"name": name of the changed widget, "value": current value of the changed widget }`` ,
        when a timeout occurs, return ``None``.

    Example:

    .. exportable-codeblock::
        :name: pin_wait_change
        :summary: `pin_wait_change()` example

        put_input('a', type='number', value=0)
        put_input('b', type='number', value=0)

        while True:
            changed = pin_wait_change('a', 'b')
            with use_scope('res', clear=True):
                put_code(changed)
                put_text("a + b = %s" % (pin.a + pin.b))

    :demo_host:`Here </markdown_previewer>` is an demo of using `pin_wait_change()` to make a markdown previewer.

    Note that: updating value with the :data:`pin` object or `pin_update()`
    does not trigger `pin_wait_change()` to return.

    When using :ref:`coroutine-based session <coroutine_based_session>`,
    you need to use the ``await pin_wait_change()`` syntax to invoke this function.
    """
    assert len(names) >= 1, "`names` can't be empty."
    if len(names) == 1 and isinstance(names[0], (list, tuple)):
        names = names[0]

    send_msg('pin_wait', spec=dict(names=names, timeout=timeout))

    return get_client_val()


def pin_update(name: str, **spec):