If you want to show us the code so you can get help with it, so you mean “How can I show code in a post”, then this is the advice. Thanks for asking. You can check you’re doing it right in the preview on the right. And afterwards, if it still isn’t right, you can edit your post until it is.
If you want to share code with others who might find it useful, then GitHub might be a good place to start. (People have given advice about how to publish a package on PyPI, but I think that is more advanced than you want.)
If you just want to show off your learning, and encourage others to try the same thing, then you could find somewhere to blog about it. You should check that it is able to display code properly. I don’t have any recommendations on where. (I’m beginning to think Medium would be a good place for my own use, but it costs money.)