Python | Tuples with maximum key of similar values

Last Updated : 11 Nov, 2019

Sometimes, while working with Python, we can have a problem in which we need to get all the records. This data can have similar values and we need to find maximum key’ed value pair. This kind of problem can occur while working with data. Let’s discuss certain ways in which this task can be done.

Method #1 : Using max() + groupby() + itemgetter() + list comprehension
The combination of above functions can be used to perform this particular task. In this, we first group the like valued elements using groupby() and itemgetter(), and then extract the maximum of those using max() and cummulate the result in list using list comprehension.

# Python3 code to demonstrate working of
# Tuples with maximum key of similar values
# using max() + groupby() + itemgetter() + list comprehension
from operator import itemgetter
from itertools import groupby
  
# initialize list
test_list = [(4, 3), (2, 3), (3, 10), (5, 10), (5, 6)]
  
# printing original list
print("The original list : " + str(test_list))
  
# Tuples with maximum key of similar values
# using max() + groupby() + itemgetter() + list comprehension
res = [max(values) for key, values in groupby(test_list, key = itemgetter(1))]
  
# printing result
print("The records retaining maximum keys of similar values : " + str(res))

Output :

The original list : [(4, 3), (2, 3), (3, 10), (5, 10), (5, 6)]
The records retaining maximum keys of similar values : [(4, 3), (5, 10), (5, 6)]

Method #2 : Using setdefault() + items() + loop + list comprehension
The combination of above functions can also achieve this task. In this, we convert the list tuple key-value pairs into a dictionary and assign a default value using setdefault(). The final result is computed using list comprehension.

# Python3 code to demonstrate working of
# Tuples with maximum key of similar values
# using setdefault() + items() + loop + list comprehension
  
# initialize list
test_list = [(4, 3), (2, 3), (3, 10), (5, 10), (5, 6)]
  
# printing original list
print("The original list : " + str(test_list))
  
# Tuples with maximum key of similar values
# using setdefault() + items() + loop + list comprehension
temp = {}
for val, key in test_list:
  if val > temp.setdefault(key, val):
    temp[key] = val
res = [(val, key) for key, val in temp.items()]
  
# printing result
print("The records retaining maximum keys of similar values : " + str(res))

Output :

The original list : [(4, 3), (2, 3), (3, 10), (5, 10), (5, 6)]
The records retaining maximum keys of similar values : [(4, 3), (5, 10), (5, 6)]

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