求网友解决下面这个问题

运行pycharm报下面这个错误:求解决方案
selenium.common.exceptions.InvalidSelectorException: Message: invalid selector: Unable to locate an element with the xpath expression //[@id="input-lastname" because of the following error:
SyntaxError: Failed to execute 'evaluate' on 'Document': The string '//[@id="input-lastname"' is not a valid XPath expression.
(Session info: chrome=92.0.4515.107)

无法定位元素，xpath写错了，不是有效的xpath表达式。