Keeping a variable around from post to get?
HTTP is stateless, so you have no (built-in) way of knowing if the user that loads one page is the same user that loaded another. Further, even if you do know that, thanks to session cookies, for example, you have no way of telling if the browser window they're loading the subsequent page in is the same one they loaded the prior page in. The user could have multiple tabs accessing your site, and you don't want one page's state change to clobber another's.
With that in mind, your best option is to include query parameters in the link to the page being fetched with GET, encoding the variables you want to send to the 'get' page (make sure they're not sensitive, since the user can modify them!). Then  you can access them through self.request.GET in the get request.
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?