How close are development webservers to production webservers?
Your staging environment should mimic your production environment. Development is more like a playground, and the control on the development environment should not be quite so strict. However, the development environment should periodically be refreshed from the production environment (e.g,. prod data copied to the dev db, close the ports on dev that are closed on prod, etc.).
Ideally, dev, stage, and prod are all on separate machines. The separate machines can be separate physical boxes, or virtual machines on the same physical box, depending on budget/needs.
Most python frameworks will have a development webserver of some kind that will have a warning that it isn't for use as production servers.  How much different do they tend to be from their production equivalents?
I haven't quite decided which framework to go with, much less what production server to use, so it's kinda difficult for me to pin this down to a "compare development server x to production server y."  So with that said, let me make the question a little bit more precise:  In your past experience with a python framework, how much time did you have to spend getting your application up and running with a production system once its been developed on a development server?  Or did you skip the development server and develop your app on a server that's more like what you will use in production?