Keeping a variable around from post to get?
I don't know specifically about the google app engine, but normally, here's what happens:
The server would have some kind of thread pool. Every time an http request is sent to the server, a thread is selected from the pool or created.
In that thread an instance of some kind of controller object will be created. This object will decide what to do with the request (like instantiating other classes and preprocessing the http request parameters). Usually, this object is the core of web frameworks. The request parameters are also resent by the browser every time (the server cannot guess what the browser wants).
Web servers usually have state stores for objects in a permanent or a session state. The session is represented by a unique user (usually by a cookie or a GUID in the url), which expires after a certain time.
Now in your case, you would need to take the values you got from your first function, store that in the session store and in the second function, get those values back from the session store.
Another solution would be to send the items back to the page as url parameters in your generated HTML from the first function and then you would get those back "as usual" from your second function.
I have a class called myClass which defines post() and get() methods. 
From index.html, I have a form with an action that calls myClass.post() which grabs some data from the data base, sets a couple variables and sends the user to new.html. 
now, new.html has a form which calls myClass.get(). 
I want the get() method to know the value of the variables I got in post(). That is is main point here.
I figure the submit from new.html creates a separate instance of myClass created by the submit from index.html. 
Is there a way to access the "post instance" somehow? 
Is there a workaround for this? If I have to, is there an established way to send the value from post to "new.html" and send it back with the get-submit? 
more generally, I guess I don't understand the life of my instances when web-programming. In a normal interactive environment, I know when the instance is created and destroyed, but I don't get that when I'm only using the class through calls to its methods. Are those classes even instantiated unless their methods are called?