How can I separate and traverse data in a list of tuples in Python 2.6?

Question

Background

Updated: Here is the horrendous list I'm working with (please excuse the list's false title). The length and data is subject to change because I'm retrieving this information from an ever-changing database.

Desired Outcome

I will further explain my purposes because I am unsure of the best way to go about this. Each number represents an ID as noted below . I need to create an XML file where Software elements have Target sub-elements based upon the SoftwareID and TargetID matching up in the tuple.

For example:

SoftwareID    TargetID                 XML Representation
----------------------------------------------------------------------
    65          115    <-- This Software element (id=65) has only one Target
                           sub-element (id=115)
    138         218    <-- This Software element (id=138) will have multiple
    138         219        Target sub-elements (ids=218, 219, 220)
    138         220 

Attempt

I've played with unpacking the sequence as done here , but the list is much too long for this implementation. I get an error that says . 。
I see now that this is actually a list of tuples instead of just a single tuple, so this wouldn't work anyway.

I've tried this implementation but get an error that says

As for the rest of my implementation, I am lost without being able to separate this stupid list.

Question

• How can I separate the data from this list of tuples in order to use it for the implementation described in the Desired Outcome section?

Answer 1

its unclear what the actual problem is ... but maybe this will help resolve the issue

data = {}
for lhs,rhs in my_list_of_tuples:

    try:
        data[lhs].append(rhs)
    except KeyError:
        data[lhs] = [rhs]

print data.items()[:5]

to explain a little more simply lets look at it differently

my_list_of_tuples = [(1,2),(3,5),(7,8),(7,9)]
for item in my_list_of_tuples:
    #on first loop item=(1,2) ; 2nd loop item=(3,5); 3rd loop item=(7,8)
    left_number = item[0] 
    right_number = item[1]
    #these 2 lines can be simplified to
    left_number,right_number = item

    #now if left number is already in the data dictionary we will append the new right number to its list
    try:
        data[left_number].append(right_number)
    except KeyError: #: if the left_number is not already in our data dictionary
        data[left_number] = [right_number] #: create a new list that contains only the right number

#now that we are done we have data that maps left numbers to right numbers
print data
#{1:[2],3:[5],7:[8,9]}