Passing variable with Python CGI

Passing variable with Python CGI

I am using Python CGI to handle a simple web interface that has the
following function:
User enters an ID in a form-field, clicks submit and gets a list of
variables back from a dictonary containing lists. With a textfield the
user can enter another item, click submit to append the value to the list
corresponding with the previously entered ID.
The first submit works well, checking whether the ID exists in the
dictionary and then prints the form field for adding a new item. But the
value of the ID is lost then. What would be the best way to pass on that
value?
Would posting the first value as GET and retrieving it through the URL be
a solution to this or is there a better way?
I have to use python & cgi for this project, without any additional
framework.
data = cgi.FieldStorage()
if data.has_key('ID'):
myID = data['myID'].value
if testme(ID): #checks if ID exists in dictionary
printmessages(myID)
addmessage(myID)
elif data.has_key('newitem'):
newmitem = data['newitem'].value
insertmessage(myID, newitem) #insert newitem to dictionary with myID