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copied!<p>Try to avoid complex nested data structures. I believe people tend to grok them only while they are intensively using the data structure. After the program is finished, or is set aside for a while, the data structure quickly becomes mystifying.</p> <p>Objects can be used to retain or even add richness to the data structure in a saner, more organized way. For instance, it appears the <code>item</code> and <code>price</code> always go together. So the two pieces of data might as well be paired in an object:</p> <pre><code>class Item(object): def __init__(self,name,price): self.name=name self.price=price </code></pre> <p>Similarly, a person seems to have an <code>id</code> and <code>name</code> and a set of possessions:</p> <pre><code>class Person(object): def __init__(self,id,name,*items): self.id=id self.name=name self.items=set(items) </code></pre> <p>If you buy into the idea of using classes like these, then your <code>list_dicts</code> could become</p> <pre><code>list_people = [ Person('001','jim',Item('pencil',0.99)), Person('002','mary',Item('book',15.49)), Person('002','mary',Item('tape',7.99)), Person('003','john',Item('pen',3.49)), Person('003','john',Item('stapler',9.49)), Person('003','john',Item('scissors',12.99)), ] </code></pre> <p>Then, to merge the people based on <code>id</code>, you could use Python's <code>reduce</code> function, along with <code>take_items</code>, which takes (merges) the items from one person and gives them to another:</p> <pre><code>def take_items(person,other): ''' person takes other's items. Note however, that although person may be altered, other remains the same -- other does not lose its items. ''' person.items.update(other.items) return person </code></pre> <p>Putting it all together:</p> <pre><code>import itertools import operator class Item(object): def __init__(self,name,price): self.name=name self.price=price def __str__(self): return '{0} {1}'.format(self.name,self.price) class Person(object): def __init__(self,id,name,*items): self.id=id self.name=name self.items=set(items) def __str__(self): return '{0} {1}: {2}'.format(self.id,self.name,map(str,self.items)) list_people = [ Person('001','jim',Item('pencil',0.99)), Person('002','mary',Item('book',15.49)), Person('002','mary',Item('tape',7.99)), Person('003','john',Item('pen',3.49)), Person('003','john',Item('stapler',9.49)), Person('003','john',Item('scissors',12.99)), ] def take_items(person,other): ''' person takes other's items. Note however, that although person may be altered, other remains the same -- other does not lose its items. ''' person.items.update(other.items) return person list_people2 = [reduce(take_items,g) for k,g in itertools.groupby(list_people, lambda person: person.id)] for person in list_people2: print(person) </code></pre>

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