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# Python | Group list items by frequency

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Examples :

`  Input:  [1, 3, 4, 4, 1, 5, 3, 1]  Output:  [(1, 3), (3, 2), (4, 2), (5, 1)]  Input:  [’x’,’ a’, ’x’ , ’y’,’ a’, ’x’]  Output:  [(’ x’, 3), (’a’, 2), (’ y’, 1)] `

Method # 1: Understanding a List

We can use lists to form tuples of each element and a counter of its occurrence and store it in & # 39; res & # 39; but it will contain a duplicate of the first element. So, to remove the duplicate first item, we use ` OrderedDict (res) .items () `.

` `

` # Python3 program to the list groupings # frequency-based elements from collections import OrderedDict     def group_list (lst):   res =   [(el, lst.count (el)) for el in lst]   return list (OrderedDict (res) .items ( ))   # Driver code lst = [ 1 , 3 , 4 , 4 , 1 , 5 , 3 , 1 ] print (group_list (lst)) `

` ` Exit:

` [(1, 3), (3, 2), (4, 2), ( 5, 1)] `

Spo int # 2: Using `collections.Counter()`

` collections.Counter () ` provides two direct methods ` keys () ` and ` values ​​() ` which provide elements and their occurrences. Finally, zip them together using the Python ` zip () ` method.

 ` # Python3 program into grouping list ` ` # frequency-based elements ` ` from ` ` collections ` ` import ` ` Counter `   ` def ` ` group_list (lst): ` ` `  ` return ` ` list ` ` (` ` zip ` ` (Counter (lst) .keys (), Counter (lst). values ​​())) `   ` # Driver code ` ` lst ` ` = ` ` [` ` 1 ` `, ` ` 3 ` `, ` ` 4 ` `, ` ` 4 ` `, ` ` 1 ` `, ` ` 5 ` `, ` ` 3 ` `, ` ` 1 ` `] ` ` print ` ` (group_list (lst)) `

Exit:

` [(1, 3), (3, 2), (4, 2), (5 , 1)] `

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