How to sort a list based on the summation of second elements of tuple within a list?

user_14455223 0
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My concern involves one of my variables which have tuples within a list as follows.

test = [(['a','b','c'],[3,2,5]),(['d','e','f'],[1,5,6]),(['g','h','j'],[1,2,4])]

I am trying to get the summation of the second tuple element of the lists for example [3,2,5] and sort them based on that summation. so the result of that summation should be.

result1 = [(['a','b','c'],[10]),(['d','e','f'],[12]),(['g','h','j'],[7])]

then my intended final result should be sorted in descending order.

result = [['d','e','f'],['a','b','c'],['g','h','j']]
tuples python-3.x python
4 Answers

An elegant one liner:

result = [a for a, b in sorted(test, key = lambda x : sum(x[1]), reverse=True)]

sorted returns a sorted list using the passed iterable, in this case test

key defines the basis for sorting. Here it's a lambda expression which takes the tuple x and returns the sum of the 2nd part of the tuple sum(x[1])

reverse is set so that sorting is in descending order

Finally we use a list comprehension to get rid of the numeric part b and keep only the alphabets a

user_136578480

I think step by step could be helpful as you mentioned you are a newbie.

  1. sum up numbers:
>>> a = [(e[0], sum(e[1])) for e in test]
>>> a
[(['a', 'b', 'c'], 10), (['d', 'e', 'f'], 12), (['g', 'h', 'j'], 7)]
  1. sort using the sum
>>> b=sorted(a, key=lambda e:-e[-1])
>>> b
[(['d', 'e', 'f'], 12), (['a', 'b', 'c'], 10), (['g', 'h', 'j'], 7)]
  1. extract only list of each item, discard sum
>>> c=[e[0] for e in b]
>>> c
[['d', 'e', 'f'], ['a', 'b', 'c'], ['g', 'h', 'j']]
user_26405290 
test = [(['a','b','c'],[3,2,5]),(['d','e','f'],[1,5,6]),(['g','h','j'],[1,2,4])]
for i in range(len(test)):
  test[i]=list(test[i])
  test[i][1]=sum(test[i][1])  #this iteration helps to sum up the elements
print(test)

new_list=[]
maxi=0
for i in test:
  if i[1]<maxi:
    new_list= new_list+[i[0]]
  else:
    new_list=[i[0]]+ new_list    #this is to sort in descending order
    maxi=i[1]
  
print(new_list)

output:

[[['a', 'b', 'c'], 10], [['d', 'e', 'f'], 12], [['g', 'h', 'j'], 7]]
[['d', 'e', 'f'], ['a', 'b', 'c'], ['g', 'h', 'j']]
>>>
user_147193400 
test = [(['a','b','c'],[3,2,5]),(['d','e','f'],[1,5,6]),(['g','h','j'],[1,2,4])]

def sum_of_list(l):
    # Returns sum of the list
    total = 0
    for val in l:
        total = total + val
    return total

def Sort_Tuple(tup):  
    # reverse = None (Sorts in Ascending order)  
    # key is set to sort using second element of  
    # sublist lambda has been used  
    tup.sort(key = lambda x: x[1], reverse = True)  
    return tup

result1 = []
for t in test:
    result1.append((t[0],sum_of_list(t[1])))
result1 = Sort_Tuple(res1)

result = [ _[0] for _ in result1]
print(result)
user_134164170
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