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Python – Cross tuple summation grouping

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  • Last Updated : 22 Jun, 2020

Sometimes, while working with Python tuple records, we can have a problem in which we need to perform summation grouping of 1st element of tuple pair w.r.t similar 2nd element of tuple. This kind of problem can have application in day-day programming. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [(1, 5), (7, 4), (9, 6), (11, 6)]
Output : [(7, 4), (1, 5), (20, 6)]

Input : test_list = [(1, 8)]
Output : [(1, 8)]

Method #1 : Using loop
This is brute force way in which this task can be performed. In this we check for similar second elements and perform summation till then and perform the accumulated grouping.




# Python3 code to demonstrate working of 
# Cross tuple summation grouping
# Using loop
  
# initializing list
test_list = [(4, 5), (7, 5), (8, 6), (10, 6), (10, 4), (6, 7), (3, 7)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Concatenate Similar Key values
# Using loop
temp = dict()
for ele1, ele2 in test_list:
    temp[ele2] = temp.get(ele2, 0) + ele1
res = [(ele2, ele1) for (ele1, ele2) in temp.items()]
  
# printing result 
print("The grouped records are : " + str(res)) 
Output :
The original list is : [(4, 5), (7, 5), (8, 6), (10, 6), (10, 4), (6, 7), (3, 7)]
The grouped records are : [(10, 4), (11, 5), (18, 6), (9, 7)]

 

Method #2 : Using groupby() + sum() + zip() + list comprehension
The combination of above functions can be used to solve this problem. In this, we perform the task of finding sum using sum(). The task of grouping is done by groupby().




# Python3 code to demonstrate working of 
# Cross tuple summation grouping
# Using groupby() + sum() + zip() + list comprehension
from itertools import groupby
  
# initializing list
test_list = [(4, 5), (7, 5), (8, 6), (10, 6), (10, 4), (6, 7), (3, 7)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Concatenate Similar Key values
# Using groupby() + sum() + zip() + list comprehension
res = [(sum(next(zip(*ele))), key) for key, ele in groupby(
                       test_list, key = lambda tup:tup[1])]
  
# printing result 
print("The grouped records are : " + str(res)) 
Output :
The original list is : [(4, 5), (7, 5), (8, 6), (10, 6), (10, 4), (6, 7), (3, 7)]
The grouped records are : [(10, 4), (11, 5), (18, 6), (9, 7)]

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