Question

The second recursion question. I need to assign unique ID’s to values in a recursive function.

Think of a folder structure, where each folder can have items or other folders. But each of those need a unique ‘id’.

I figured, since I can’t use any global variables in my recursive functions in python, that I’d increment the id with each call. But I couldn’t be more wrong. Think of the following situation.

1 – Folder

2- Folder

3 – Item

4 – Item

2 – Folder

Because of the way the recursion works, the id gets assigned twice, and there’d be no way to check. How would I go and do this? (I’m using python. Whenever I have a variable ‘uniqueid’ that I increment I get the error:

local variable ‘uniqueid’ referenced before assignment

)
My code: make_link_item just returns a string.

def build_xml(node,depth,itemid):
    #if 'Children' in node:
        #print colleges
    depth += 1
    for child in node['Children']:
        itemid += 1
        print ("  " * (depth - 1)) + "<item identifier=\"%s\" identifierref=\"%s\">" % (("itm" + ("%05d" % itemid)),("res" + ("%05d" % itemid)))
        print ("  " * depth) + "<title>%s</title>" % child['Name'].encode('utf-8')
        build_xml(child,depth,itemid)
        print ("  " * (depth - 1)) + "</item>"
    lectures = getlectures(node['Id'])
    if lectures:
        build_lectures(lectures,itemid,itemid)

def build_lectures(lectures,itemid,parentid):
    for x in range(len(lectures)):
        itemid += 1
        if x % 2 == 0:
            print "<item identifier=\"%s\" identifierref=\"%s\">" % (("itm" + ("%05d" % itemid)),("res" + ("%05d" % itemid)))
            print "<title>" + lectures[x].encode('utf-8') + "</title>"
            print "</item>"
        else:
            make_link_item(lectures[x-1].encode('utf-8'),lectures[x].encode('utf-8'),itemid,parentid)

Thanks,

Mats

Answer 1

I hope I don’t miss the question.

You could go with a class Builder that is the object for building xml arborescence. Your class has got a member increment, which you increment by one each time you meet a new item. This way, there are no two same IDs.

class Builder:

   def __init__(self):
        self.increment = 0

   #other methods you need