 # Python | Aggregate values ​​across tuple keys

Method # 1: Using ` Counter () ` + Expression Generator
A combination of the above functions can be used to accomplish this specific task. In this we need to first combine the same key elements and the aggregation task is performed by ` Counter () `.

 ` # Python3 code to demonstrate how it works ` ` # Aggregate values ​​by tuple keys ` ` # using Counter () + generator expression ` ` from ` ` collections ` ` import ` ` Counter ` ` `  ` # initialize the list ` ` test_list ` ` = ` ` [(` ` `gfg` ` `, ` ` 50 ` `), (` ` `is` ` `, 30 ), ( `best` , 100 ), ````   ( `gfg` , 20 ), ( `best` , 50 )]   # printing the original list print ( "The original list is:" + str (test_list))   # Aggregate values ​​by keys tuple # using Counter () + generator expression res = list (Counter (key for key, num in test_list  for idx in range (num)). items ())   # print result print ( " List after grouping: " + str (res) ) ```

Output:

` The original list is: [(`gfg`, 50), (` is`, 30), (`best `, 100), (` gfg`, 20), (`best`, 50)] List after grouping: [(` best`, 150), (`gfg`, 70), (` is`, 30)] `

Method # 2: Using ` groupby () + map () + itemgetter () + sum () `
Combination the above functions can also be used to accomplish this specific task. In doing so, we group the items using groupby (), the key index solution is given by itemgetter. The task of addition (aggregation) is performed by the sum () function, and the expansion of the logic for all tuples — map ().

 ` # Python3 code to demonstrate how it works ` ` # Aggregate values ​​by tuple keys ` ` # using groupby () + map () + itemgetter () + sum () ` ` from ` ` itertools ` ` import ` ` groupby ` ` from ` ` operator ` ` import ` ` itemgetter `   ` # initialize the list ` ` test_list ` ` = ` ` [(` ` ` gfg` ` `, ` ` 50 ` `), (` ` `is` ` `, ` ` 30 ` `), (` ` `best` ` `, ` ` 100 ` `), ` ` ` ` (` `` gfg` ` `, ` ` 20 ` `), (` ` `best` ` `, ` ` 50 ` `)] `   ` # print original list ` ` print ` ` (` ` "The original list is:" ` ` + ` ` str ` ` (test_list)) ` ` `  ` # Aggregate values ​​by key am tuple ` ` # using groupby () + map () + itemgetter () + sum () ` ` res ` ` = ` ` [(key, ` ` sum ( map (itemgetter ( 1 ), ele))) ```` for key, ele in groupby ( sorted (test_list, key = itemgetter ( 0 )),  key = itemgetter ( 0 ))]    # print result print ( "List after grouping:" + str (res)) ```

Output:

` The original list is: [(`gfg`, 50), (` is`, 30) , (`best`, 100), (` gfg`, 20), (`best`, 50)] List after grouping: [(` best`, 150), (`gfg`, 70), (` is` , 30)] `