sort list on multiple attribute in multiple order in python in c++ style of sorting

Question

listOfDict = [{"sal":1000,"age":25},{"sal":1000,"age":24}, {"sal":1000,"age":26},{"sal":2000,"age":25},{"sal":3000,"age":24}]

Expected o/p : [{"sal":3000,"age":24}, {"sal":2000,"age":25}, {"sal":1000,"age":24}, {"sal":1000,"age":25},{"sal":1000,"age":26}]

I want to sort this in decreasing order of salary and increasing order of age.

I tried c++ style like this:

def auxsort(p1data, p2data):   
    if p1data['sal'] > p2data['sal']:   
        return True
    if p1data['age'] <= p2data['age']:
        return True
    return False

sorted(listOfDict,key=auxsort)

But this is not allowed in python. TypeError: auxsort() takes exactly 2 arguments (1 given)

How to solve this? Thank you

https://docs.python.org/3.5/library/functions.html#sorted: "key specifies a function of one argument that is used to extract a comparison key from each list element". Also, your `auxsort` returns `None` (instead of False) if both conditionals fail. — Leporello, May 15 '19 at 16:03

score 1 · Accepted Answer · edited May 15 '19 at 16:02

1

You used the key wrong. It should take an element from listOfDict and return something that can directly compare against each other. I suggest the following instead:

def auxsort(p1data): 
    return (-p1data['sal'], p1data['age'])

this returns a tuple of two elements. If tuples t1 < t2 is means the element they correspond to also have such ordering in the sorted output.

edited May 15 '19 at 16:02

wim

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answered May 15 '19 at 16:01

adrtam

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sort list on multiple attribute in multiple order in python in c++ style of sorting

1 Answers1