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using a dictionary after it's been unpickled (in Python)

Discussion in 'Python' started by Noodle, Jul 26, 2006.

  1. Noodle

    Noodle New Member

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    This is actually a homework assingment, so I'm not looking for a direct answer, but maybe a point in the right direction. The assingment is make this program not "forget" all the information the user entered everytime it ends. (using pickle). I added the nodePickle() and nodeUnpickle() and a few other things (I noted the things I added in the comments, the rest is the orginal program)

    The problem I have, is that when I try to send the var ('item') holding the dictionary to the Qnode class (after I've loaded it from the file) , I get this error: "cannot concatenate 'str' and 'instance' objects." So, I'm not really sure what is going on here. The lesson plan really doesn't go into detail about this, so I'm kinda lost.
    Code:
    # questor.py		
    import cPickle as p
    
    # define some constants for future use
    
    kQuestion = 'question'
    kGuess = 'guess'
    nodeFile = 'questFile.txt' # jason added
    
    
    # define a function for asking yes/no questions
    def yesno(prompt):
    	ans = raw_input(prompt)
    	return (ans[0]=='y' or ans[0]=='Y')
    
    # I added; dump dictionary to file for future use
    def nodePickle(nodes):
            f = file(nodeFile, 'w')
            p.dump(nodes, f)
            f.close
            f = file(nodeFile)
            theNode = p.load(f)
            print(theNode)
    
    # I added; load dictionary from file
    def nodeUnpickle():
            f = file(nodeFile)
            nodes = p.load(f)
            f.close
            return nodes
    
    # define a node in the question tree (either question or guess)
    class Qnode:
    	
    	# initialization method
    	def __init__(self,guess):
    		self.nodetype = kGuess
    		self.desc = guess
    
    	# get the question to ask	
    	def query(self):
    		if (self.nodetype == kQuestion):
    			return self.desc + " "
    		elif (self.nodetype == kGuess):
    			return "Is it a " + self.desc + "? "
    		else:
    			return "Error: invalid node type!"
    
    	# return new node, given a boolean response
    	def nextnode(self,answer):
    		return self.nodes[answer]
    
    	# turn a guess node into a question node and add new item
    	# give a question, the new item, and the answer for that item
    	def makeQuest( self, question, newitem, newanswer ):
    
    		# create new nodes for the new answer and old answer
    		newAnsNode = Qnode(newitem)
    		oldAnsNode = Qnode(self.desc)
                    print ("newAns: ", newAnsNode)
                    print ("oldAns: ", oldAnsNode)
                    
    		# turn this node into a question node
    		self.nodetype = kQuestion
    		self.desc = question
    
    		# assign the yes and no nodes appropriately
    		self.nodes = {newanswer:newAnsNode, not newanswer:oldAnsNode}
                    nodePickle(self.nodes) # I added
                  
    
    def traverse(fromNode):
    	# ask the question
    	yes = yesno( fromNode.query() )
    	
    	# if this is a guess node, then did we get it right?
    	if (fromNode.nodetype == kGuess):
    		if (yes):
    			print "I'm a genius!!!"
    			return
    		# if we didn't get it right, return the node
    		return fromNode
    	
    	# if it's a question node, then ask another question
    	return traverse( fromNode.nextnode(yes) )
    
    def run(item):   
            # start with a single guess node
    	topNode = Qnode(item[0]) # orignal program read 'topNode = Qnode('python')
    	
    	done = 0
    	while not done:
    		# ask questions till we get to the end
    		result = traverse( topNode )
    		
    		# if result is a node, we need to add a question
    		if (result):
    			item = raw_input("OK, what were you thinking of? ")
    			print "Enter a question that distinguishes a",
    			print item, "from a", result.desc + ":"
    			q = raw_input()
    			ans = yesno("What is the answer for " + item + "? ")
    			result.makeQuest( q, item, ans )
    			print "Got it."
    		
    		# repeat until done
    		print
    		done = not yesno("Do another? ")
    		print
    
    
    # immediate-mode commands, for drag-and-drop or execfile() execution
    if __name__ == '__main__':
            item = nodeUnpickle()# I added; get dictionary from file
    	run(item)
    	print
    	raw_input("press Return>")
    else:
    	print "Module questor imported."
    	print "To run, type: questor.run()"
    	print "To reload after changes to the source, type: reload(questor)"
    
    # end of questor.py

    Also, as a side question.... how come when I load the dictionary into a var and try to "print" it... it gives me the memory address instead of the dictionary. I.E....

    >>> item = p.load(f)
    >>> item
    {False: <__main__.Qnode instance at 0x016E8080>, True: <__main__.Qnode instance at 0x016E8058>}

    or

    >>> item[0]
    <__main__.Qnode instance at 0x016E8080>

    Any help on these issue are appreciated, thanks in advance!

    -Noodle
     

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