factory_client does whatever you want it to do - it's just the method that would call your Abstract Factory or Factory Method or whatever.
I've never used Spring, but I assume that the wiring it does is similar to JSF managed beans, eg. you give it an XML config file and it takes care of creating the appropriate Java objects from that. As for how you'd do it in Python - you wouldn't. To quote Phillip Eby: "XML is not the answer. It is not even the question."
That's because XML is usually easier to write than Java but harder to write than Python, so you're better off just writing the Python.
You'd write your classes, and then stick them in a data structure somewhere. You could even use the package structure of your app as that data structure - have the client code receive a module (modules and packages are first-class in Python), then use getattr to pull out the class object. Then when you have a class object, you call it to create a new instance.
I suppose if you want some security guarantees, you'd explicitly specify the classes that may be passed in to the method. For example, in my own app, I have a bunch of classes that essentially represent language constructs in a visual domain-specific language, each of which has a "default" value so that when the user's clicking away they don't have to type in code from scratch. I wanted to expose these defaults to JavaScript, the language of the UI. So I put together a dictionary of the classes that I want exposed, then loop through it, instantiate each class as the default, encode each object as a plain old dictionary (they all have a 'props' method that returns the object represented as a JSON-suitable dictionary), and JSON-encode the whole mess. It totals like 5 lines for the whole thing, not counting the list of classes to be exposed.
I don't think Java Reflection is a/the problem.