Finding "src" from Element

Hi, I'm trying to get a link from element <video crossorigin="anonymous" id="mainvideo" width="100%" height="100%" poster="blablablabla" playsinline="" preload="metadata" style="width: 952px; height: 480px;" src="**__I WANT TO GET WHAT IS IN HERE__**"> </video> How can I only get the inside of the src? I have it this saved as a string. Thanks!