Python sort a list by two values

Question

I'm trying to sort this list first by name in reverse. Then, after the first set of results (where flag = "ZAR"), I want to sort the remaining elements by time not in reverse:

import operator
list = [
    {"flag":"ZAR", "time":"17:45"},
    {"flag":"AUS", "time":"17:30"},
    {"flag":"AUS", "time":"17:15"},
    {"flag":"USA", "time":"17:00"},
    {"flag":"GBP", "time":"16:55"},
    {"flag":"ZAR", "time":"16:45"},
    {"flag":"USA", "time":"16:35"},
    {"flag":"GBP", "time":"16:25"},
    {"flag":"ZAR", "time":"16:15"},
]

list.sort(key=operator.itemgetter("time"))
list.sort(key=operator.itemgetter("flag"),reverse=True)


print list

[{'flag': 'ZAR', 'time': '16:15'}, {'flag': 'ZAR', 'time': '16:45'}, {'flag': 'ZAR', 'time': '17:45'}, {'flag': 'USA', 'time': '16:35'}, {'flag': 'USA', 'time': '17:00'}, {'flag': 'GBP', 'time': '16:25'}, {'flag': 'GBP', 'time': '16:55'}, {'flag': 'AUS', 'time': '17:15'}, {'flag': 'AUS', 'time': '17:30'}]

As you can see the flag sort was done correctly, but the other elements are only sorted by time within the sorted country.

What I want is to always have the ZAR first and after that it does not matter what the flag name is, only the time. So it should give this result:

[{'flag': 'ZAR', 'time': '16:15'}, {'flag': 'ZAR', 'time': '16:45'}, {'flag': 'ZAR', 'time': '17:45'}, {'flag': 'GBP', 'time': '16:25'}, {'flag': 'USA', 'time': '16:35'}, {'flag': 'GBP', 'time': '16:55'}, {'flag': 'USA', 'time': '17:00'}, {'flag': 'AUS', 'time': '17:15'}, {'flag': 'AUS', 'time': '17:30'}]

How would this be done?

The worst possible name for a list is list. Do not shadow built-ins. — Burhan Khalid
– Burhan Khalid, Commented Sep 2, 2013 at 11:21
You need to clarify your requirement - you're not "sorting a list by two values" in the normal sense of the word. Can you confirm: you want all the ZAR values first (sorted by time or not?) and then you want the remainder of the elements sorted by time regardless of flag value - is that right? — Vicky
– Vicky, Commented Sep 2, 2013 at 11:27

Jon Clements · Accepted Answer · 2013-09-02 11:20:46Z

5

Amend your code to:

import operator
data = [
    {"flag":"ZAR", "time":"17:45"},
    {"flag":"AUS", "time":"17:15"},
    {"flag":"USA", "time":"17:00"},
    {"flag":"GBP", "time":"16:55"},
    {"flag":"ZAR", "time":"16:45"},
    {"flag":"USA", "time":"16:35"},
    {"flag":"GBP", "time":"16:25"},
    {"flag":"ZAR", "time":"16:15"},
]

data.sort(key=operator.itemgetter("time"))
data.sort(key=lambda L: L['flag'] == 'ZAR', reverse=True)

# [{'flag': 'ZAR', 'time': '16:15'}, {'flag': 'ZAR', 'time': '16:45'}, {'flag': 'ZAR', 'time': '17:45'}, {'flag': 'GBP', 'time': '16:25'}, {'flag': 'USA', 'time': '16:35'}, {'flag': 'GBP', 'time': '16:55'}, {'flag': 'USA', 'time': '17:00'}, {'flag': 'AUS', 'time': '17:15'}, {'flag': 'AUS', 'time': '17:30'}]

answered Sep 2, 2013 at 11:20

Jon Clements

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1 Comment

Harry Over a year ago

Ah there we go! Makes much more sense! Thanks

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