Question

I’m building an app where you can search for objects in a database (let’s assume the objects you search for are persons). What I want to do is to group related objects, for example married couples. In other words, if two people share the same last name, we assume that they are married (not a great example, but you get the idea). The last name is the only thing that identifies two people as married.
In the search results I want to display the married couples next to each other, and all the other persons by themselves.

Let’s say you search for “John”, this is what I want:

John Smith - Jane Smith
John Adams - Nancy Adams
John Washington
John Andersson
John Ryan

Each name is then a link to that person’s profile page.

What I have right now is a function that finds all pairs, and returns a list of tuples, where each tuple is a pair. The problem is that on the search results, every name that is in a pair is listed twice.
I do a query for the search query (Person.objects.filter(name__contains=”John”)), and the result of that query is sent to the match function. I then send both the original queryset and the match function result to the template.
I guess I could just exclude every person that the match function finds a match for, but I don’t know, but is that the most efficient solution?

Edit:

As I wrote in a comment, the actual strings that I want to match are not identical. To quote myself:

In fact, the strings I want to match are not identical, instead they
look more like this: “foo2(bar13)” – “foo2(bar14)”. That is, if two
strings have the same foo id (2), and if the bar id is an odd number
(13), then its match is the bar id + 1 (14). I have a regular
expression to find these matches

Answer 1

First get your objects sorted by last name:

def keyfun(p):
    return p.name.split()[-1]

persons = sorted(Person.objects.all(), key = keyfun)

Then use groupby:

from itertools import groupby
for lname, persons in groupby(persons, keyfun):
    print ' - '.join(p.name for p in persons)

Update Yes, this solution works for your new requirement too. All you need is a stable way to generate keys for each item, and replace the body of the keyfun with it:

from re import findall
def keyfun(p):
    v1, v2 = findall(p.name, '\d+')
    tot = int(v1) + int(v2) % 2
    return tot

Your description for how to generate the key for each item is not clear enough, although you should be able to figure it out yourself with the above example.