Complex sort in python

Question

I have the following list of tuples:

items = [
    ('john jones', ['Director', 'Screenwriter', 'Producer']), 
    ('eric smith', ['Screenwriter']), 
    ('anne smith', ['Producer']), 
    ('emily smith', ['Director']), 
    ('steven jones', ['Director', 'Screenwriter'])
]

I need to sort it such that "Director" appears before "Screenwriter" appears before "Producer". The actual ordering therein doesn't matter. For example, this would be a valid outcome:

items = [
    ('john jones', ['Director', 'Screenwriter', 'Producer']), 
    ('emily smith', ['Director']), 
    ('steven jones', ['Director', 'Screenwriter'])
    ('anne smith', ['Producer']), 
    ('eric smith', ['Screenwriter']), 
]

Is there a way to do this sort doing sorted(items, key=lambda x: ?), or do I have to iterate each item in the list?

A collections.OrderedDict might be an appropriate structure here. — Gareth Latty
– Gareth Latty, Commented Jun 15, 2012 at 18:48

jamylak · Accepted Answer · 2012-06-18 06:01:48Z

3

Of course, there is a way:

$ cat sort.py
order = ['Director', 'Screenwriter', 'Producer']
items = [
    ('john jones', ['Director', 'Screenwriter', 'Producer']), 
    ('eric smith', ['Screenwriter']), 
    ('anne smith', ['Producer']), 
    ('emily smith', ['Director']), 
    ('steven jones', ['Director', 'Screenwriter'])
]

for i in sorted(items, key = lambda x: order.index(x[1][0])):
    print i

Let's try it:

$ python sort.py
('john jones', ['Director', 'Screenwriter', 'Producer'])
('emily smith', ['Director'])
('steven jones', ['Director', 'Screenwriter'])
('eric smith', ['Screenwriter'])
('anne smith', ['Producer'])

And when you want to sort equal eintries by name, you just need a tuple (Lattyware 's idea):

for i in sorted(items, key = lambda x: (order.index(x[1][0]), x[0])):
    print i

edited Jun 18, 2012 at 6:01

jamylak

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answered Jun 15, 2012 at 18:45

Igor Chubin

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6 Comments

Gareth Latty Over a year ago

This works, and was my initial thought, but I actually prefer the dictionary approach that Joel Cornett's answer uses - it's more explicit and clear. It might be worth making it go to a tuple of ordering, name so that it sorts on name after ordering, rather than being in the order they were.

Igor Chubin Over a year ago

@Lattyware: That is not a problem at all. You just need to specify lambda x: correct_ordering.get(x[1][0], 999) instead of index. By the way "dictionary approach" is better because you need not to specify all "levels". That that are not specified will be at the end of the sorted list.

Gareth Latty Over a year ago

Was that comment in reply to me? I don't really see how it applies to what I said.

Igor Chubin Over a year ago

@Lattyware: Why do you not see it? That is a "dictionary approach". Did you mean something else?

Gareth Latty Over a year ago

Sorry, reading it again I see what you meant - it was just that you offered improvements while talking about it, it threw me. Note that float("inf") to get infinity might be better than an arbitrary 999.

|

Community · Accepted Answer · 2017-05-23 11:49:11Z

0

Here is what I consider the best overall solution, mainly a mashup of other answers here:

import collections

items = collections.OrderedDict([
    ('john jones', ['Director', 'Screenwriter', 'Producer']),
    ('emily smith', ['Director']),
    ('steven jones', ['Director', 'Screenwriter']),
    ('anne smith', ['Producer']),
    ('eric smith', ['Screenwriter']),
])

ordering = {'Director': 1, 'Screenwriter': 2, 'Producer': 3}

def order(item):
    name, values = item
    return ordering.get(values[0], float("inf")), name

print(sorted(items.items(), key=order))

Giving us:

[('emily smith', ['Director']), ('john jones', ['Director', 'Screenwriter', 'Producer']), ('steven jones', ['Director', 'Screenwriter']), ('eric smith', ['Screenwriter']), ('anne smith', ['Producer'])]

And roles not in the ordering dict will be placed at the end. They will be first sorted by role, then by name.

This presumes the sublists are pre-sorted. If not, it is easy to sort them first.

edited May 23, 2017 at 11:49

CommunityBot

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answered Jun 15, 2012 at 19:02

Gareth Latty

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2 Comments

jdi Over a year ago

I still feel like the use of OrderedDict is assuming the OP manually populates the source dict and not just gets it from some other return value.

Gareth Latty Over a year ago

@jdi That's a valid point, but it's pretty easy to change this not to use one.

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