Python | Delete elements with frequency atmost K
There are many methods that can be employed to perform the deletion in the list. Be it remove function, pop function and many other functions. But most of the times, we usually don’t deal with the simple deletion, but with certain constraints. This article discusses certain ways in which we can delete only those elements which occurs less than K times.
Method #1 : Using list comprehension + count()
The idea applied here is to construct a new list using list comprehension and insert only those elements which occur more than K times. The count operation is done with the help of count function.
# Python3 code to demonstrate# remove elements less than and equal K # using list comprehension + count() # initializing listtest_list = [1, 4, 3, 2, 3, 3, 2, 2, 2, 1] # printing original listprint("The original list : " + str(test_list)) # initializing KK = 2 # using list comprehension + count()# remove elements less than K res = [ i for i in test_list if test_list.count(i) > K] # print resultprint("The list removing elements less than and equal K : " + str(res)) |
The original list : [1, 4, 3, 2, 3, 3, 2, 2, 2, 1] The list removing elements less than and equal K : [3, 2, 3, 3, 2, 2, 2]
Method #2 : Using Counter() + list comprehension
This problem can be efficiently solved using the Counter function that precomputes the count of each elements in list so that the decision to keep or reject a particular element takes lesser time.
# Python3 code to demonstrate# remove elements less than and equal K # using Counter() + list comprehensionfrom collections import Counter # initializing listtest_list = [1, 4, 3, 2, 3, 3, 2, 2, 2, 1] # printing original listprint("The original list : " + str(test_list)) # initializing KK = 2 # using Counter() + list comprehension# remove elements less than K freq = Counter(test_list)res = [ele for ele in test_list if freq[ele] > K] # print resultprint("The list removing elements less than and equal K : " + str(res)) |
The original list : [1, 4, 3, 2, 3, 3, 2, 2, 2, 1] The list removing elements less than and equal K : [3, 2, 3, 3, 2, 2, 2]
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