I always forget how to access information about classes and methods - how to do it?

I know one can access information about python3 classes and methods
(e.g. list the methods in a class, show the parameters for a method,
etc.) but I always forget how to do it.

Can someone enlighten me please, plus tell me where it is documented
so that I can bookmark it and not need to ask again.

-- 
Chris Green
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