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Python | Custom sorting in list of tuples
  • Last Updated : 11 May, 2020

Sometimes, while working with list of tuples, we can have a problem in which we need to perform it’s sorting. Naive sorting is easier, but sometimes, we have to perform custom sorting, i.e by decreasing order of first element and increasing order of 2nd element. And these can also be in cases of different types of tuples. Let’s discuss certain cases and solutions to perform this kind of custom sorting.

Method #1 : Using sorted() + lambda
This task can be performed using the combination of above functions. In this, we just perform the normal sort, but in addition we feed a lambda function which handles the case of custom sorting discussed above.

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# Python3 code to demonstrate working of
# Custom sorting in list of tuples
# Using sorted() + lambda
  
# Initializing list
test_list = [(7, 8), (5, 6), (7, 5), (10, 4), (10, 1)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Custom sorting in list of tuples
# Using sorted() + lambda
res = sorted(test_list, key = lambda sub: (-sub[0], sub[1]))
  
# printing result
print("The tuple after custom sorting is : " + str(res))

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Output :

The original list is : [(7, 8), (5, 6), (7, 5), (10, 4), (10, 1)]
The tuple after custom sorting is : [(10, 1), (10, 4), (7, 5), (7, 8), (5, 6)]

 

Method #2 : Using sorted() + lambda() + sum() ( With sum of tuple condition)
In this method, similar solution sustains. But the case here is that we have tuple as the 2nd element of tuple and its sum has to considered for sort order. Other functions than summation can be extended in similar solution.



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# Python3 code to demonstrate working of
# Custom sorting in list of tuples
# Using sorted() + lambda() + sum()
  
# Initializing list
test_list = [(7, (8, 4)), (5, (6, 1)), (7, (5, 3)), (10, (5, 4)), (10, (1, 3))]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Custom sorting in list of tuples
# Using sorted() + lambda() + sum()
res = sorted(test_list, key = lambda sub: (-sub[0], sum(sub[1])))
  
# printing result
print("The tuple after custom sorting is : " + str(res))

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Output :

The original list is : [(7, (8, 4)), (5, (6, 1)), (7, (5, 3)), (10, (5, 4)), (10, (1, 3))]
The tuple after custom sorting is : [(10, (1, 3)), (10, (5, 4)), (7, (5, 3)), (7, (8, 4)), (5, (6, 1))]

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