Many Karateka practice the world over, in order from least advanced (the Kihon kata) to most advanced. The Heian forms, as you move up, and the Katas become more and more advanced. The entire striking curriculum of Karate, and some of the grappling, can be found in those Katas. However the Katas are not the whole of Karate; there are many grappling techniques, not included in the Kata Bunkai. Bunkai means "application."
Also, the grappling in the authentic style of Shotokan, is all standup, there is absolutely no ground work outside hitting someone once you get them down. Moreover, the grappling techniques Gichin Funakoshi specifically requested from Dr. Kano, when the latter offered to teach him some Judo in exchange for some Karate, are all strictly defensive. Offensively, Shotokan's grappling is worthless, it can not be used in a sports competition. The reasons for that have to do with the fact that it is not designed for scoring points, or merely submitting, grappling in Karate is designed to incapacitate and prevent further attacks. The second reason has to do with the fact that applying Karate grappling is very difficult, it requires a lot of precise movement.
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The best place to learn any Martial Arts form is underneath a trained instructor. It's much safer than learning from Karate for dummies for many reasons. With an instructor you learn the proper technique for execution which can keep you from injuring yourself. Also, when learning from an instructor you have someone to interact with in order to learn the application which, again, can minimize risk of injury and ensure that you really know how to defend yourself. Also, there is a lot of philosophy that you can't just learn from a book, it's best to be taught be someone experienced.