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Python Program to Extract Elements from list in set
• Last Updated : 05 Apr, 2021

Given a list, the task is to write a Python Program to extract all the elements with its occurrence matching in set.

Input : test_list = [5, 6, 2, 3, 2, 6, 5, 8, 9], search_set = {6, 2, 8}

Output : [6, 2, 2, 6, 8]

Explanation : 2, 6 occur twice and in order with respect to other elements is output.

Input : test_list = [5, 6, 2, 3, 2, 6, 5, 8, 9], search_set = {8, 3, 5}

Output : [5, 3, 5, 8]

Explanation : 5 occurs twice and in order with respect to other elements is output.

Method #1 : Using loop

In this, each list element is iterated and checked for its presence in set using in operator and appended to result if found.

## Python3

 `# Python3 code to demonstrate working of``# Elements from list in set``# Using loop`` ` `# initializing list``test_list ``=` `[``5``, ``6``, ``2``, ``3``, ``2``, ``6``, ``5``, ``8``, ``9``]``              ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing search set``search_set ``=` `{``6``, ``2``, ``8``}`` ` `res ``=` `[]``for` `ele ``in` `test_list:``     ` `    ``# check if element is present in set``    ``if` `ele ``in` `search_set:``        ``res.append(ele)`` ` `# printing result``print``(``"Set present list elements : "` `+` `str``(res))`

Output:

```The original list is : [5, 6, 2, 3, 2, 6, 5, 8, 9]
Set present list elements : [6, 2, 2, 6, 8]```

Method #2 : Using repeat() + from_iterable() + count()

In this, we test for each set element in list and repeat using repeat() by the count required to be computed using count(). The order is not maintained in this result.

## Python3

 `# Python3 code to demonstrate working of``# Elements from list in set``# Using repeat() + from_iterable() + count()``from` `itertools ``import` `chain, repeat`` ` `# initializing list``test_list ``=` `[``5``, ``6``, ``2``, ``3``, ``2``, ``6``, ``5``, ``8``, ``9``]``              ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing search set``search_set ``=` `{``6``, ``2``, ``8``}`` ` `# repeat repeats all the occurrences of elements``res ``=` `list``(chain.from_iterable((repeat(ele, test_list.count(ele)) ``                                ``for` `ele ``in` `search_set)))`` ` `# printing result``print``(``"Set present list elements : "` `+` `str``(res))`

Output:

```The original list is : [5, 6, 2, 3, 2, 6, 5, 8, 9]
Set present list elements : [6, 2, 2, 6, 8]```

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