Python - Maximum of Similar Keys in Tuples

Python – Maximum of Similar Keys in Tuples

Last Updated : 10 Jul, 2020

Sometimes, while working with Python tuples, we can have a problem in which we need to perform maximum of all values of the equal keys in Tuple list. This kind of application in useful in many domains such as web development and day-day programming. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [(4, 8), (4, 2), (4, 2), (4, 6)]
Output : [(4, 18)]
Input : test_list = [(1, 8), (2, 2), (3, 6), (4, 2)]
Output : [(1, 8), (2, 2), (3, 6), (4, 2)]

Method #1 : Using max() + groupby() + lambda + loop
The combination of above functions can be used to solve this problem. In this, we perform the task of grouping using groupby() and maximum is extrated using max(), and result is compiled using loop.

# Python3 code to demonstrate working of 
# Maximum of Similar Keys in Tuples
# Using max() + groupby() + lambda + loop
from itertools import groupby
  
# initializing lists
test_list = [(4, 8), (3, 2), (2, 2), (4, 6), (3, 7), (4, 5)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Maximum of Similar Keys in Tuples
# Using max() + groupby() + lambda + loop
test_list.sort(key = lambda sub: sub[0]) 
temp = groupby(test_list, lambda ele: ele[0])
res = []
for key, val in temp:
    res.append((key, sum([ele[1] for ele in val])))
  
# printing result 
print("Maximum grouped elements : " + str(res))

Output :

The original list is : [(4, 8), (3, 2), (2, 2), (4, 6), (3, 7), (4, 5)]
Maximum grouped elements : [(2, 2), (3, 7), (4, 8)]

Method #2 : Using max() + groupby() + itemgetter() + list comprehension
The combination of above functions can be used to solve this problem. In this, we perform similar task as above, the second element is chosen using itemgetter and list comprehension is used to compile elements and extract result.

# Python3 code to demonstrate working of 
# Maximum of Similar Keys in Tuples
# Using max() + groupby() + itemgetter() + list comprehension
from itertools import groupby
from operator import itemgetter
  
# initializing lists
test_list = [(4, 8), (3, 2), (2, 2), (4, 6), (3, 7), (4, 5)]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Maximum of Similar Keys in Tuples
# Using max() + groupby() + itemgetter() + list comprehension
temp = groupby(sorted(test_list, key = itemgetter(0)), key = itemgetter(0))
res = [(key, max(map(itemgetter(1), sub))) for key, sub in temp]
  
# printing result 
print("Maximum grouped elements : " + str(res))

Output :

The original list is : [(4, 8), (3, 2), (2, 2), (4, 6), (3, 7), (4, 5)]
Maximum grouped elements : [(2, 2), (3, 7), (4, 8)]

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