title: How to check in python if some class (by string name) exists?
body: <p>Is it possible to check if some class exists? I have class names in a json config file. 
  I know that I can simply try to create an object by class name string but that is  actually a bad idea because the class constructor can do some unexpected stuff while at this point in time I just want to check if my config is valid and all mentioned classes are available. </p>
  
  <p>Is there any way to do it? </p>
  
  <p>EDIT: Also I do understand that u can get all the methods from some module, in my case I am not sure and don't actually care from what module comes the method. It can be from any import statement and I probably don't know where exactly from.</p>