# Python – Squash consecutive values of K

Sometimes, while working with Python lists, we can have a problem in which we need to perform removal of duplicate consecutive values of particular element. This kind of problem can have application in many domains such as competitive programming and web development. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [4, 5, 5, 4, 3, 3, 5, 5, 5, 6, 5], K = 3
Output : [4, 5, 5, 4, 3, 5, 5, 5, 6, 5]

Input : test_list = [1, 1, 1, 1], K = 1
Output : [1]

Method #1 : Using `zip()` + yield
The combination of above functions provide one of the ways to solve this problem. In this, we perform the task of checking consecution duplications using zipping current and next element list, and yield is used to render the element basis of condition.

 `# Python3 code to demonstrate working of  ` `# Squash consecutive values of K ` `# Using zip() + yield ` ` `  `# helper function ` `def` `hlper_fnc(test_list, K): ` `    ``for` `sub1, sub2 ``in` `zip``(test_list, test_list[``1``:]): ` `        ``if` `sub1 ``=``=` `sub2 ``=``=` `K: ` `            ``continue` `        ``else``: ` `            ``yield` `sub1 ` `    ``yield` `sub2        ` ` `  `# initializing list ` `test_list ``=` `[``4``, ``5``, ``5``, ``4``, ``3``, ``3``, ``5``, ``5``, ``5``, ``6``, ``5``]  ` ` `  `# printing original list ` `print``(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# initializing K  ` `K ``=` `5` ` `  `# Squash consecutive values of K ` `# Using zip() + yield ` `res ``=` `list``(hlper_fnc(test_list, K)) ` ` `  `# printing result  ` `print``(``"List after filteration : "` `+` `str``(res)) `

Output :

```The original list is : [4, 5, 5, 4, 3, 3, 5, 5, 5, 6, 5]
List after filteration : [4, 5, 4, 3, 3, 5, 6, 5]
```

Method #2 : Using `yield + groupby()`
The combination of above functions can be used to solve this problem. In this, we perform the task of grouping using groupby(), for checking consecutions, and yield is used to return valid elements.

 `# Python3 code to demonstrate working of  ` `# Squash consecutive values of K ` `# Using yield + groupby() ` `import` `itertools ` ` `  `# helper function ` `def` `hlper_fnc(test_list, K): ` `    ``for` `key, val ``in` `itertools.groupby(test_list): ` `        ``if` `key ``=``=` `K: ` `            ``yield` `key ` `        ``else``: ` `            ``yield` `from` `val     ` ` `  `# initializing list ` `test_list ``=` `[``4``, ``5``, ``5``, ``4``, ``3``, ``3``, ``5``, ``5``, ``5``, ``6``, ``5``]  ` ` `  `# printing original list ` `print``(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# initializing K  ` `K ``=` `5` ` `  `# Squash consecutive values of K ` `# Using yield + groupby() ` `res ``=` `list``(hlper_fnc(test_list, K)) ` ` `  `# printing result  ` `print``(``"List after filteration : "` `+` `str``(res)) `

Output :

```The original list is : [4, 5, 5, 4, 3, 3, 5, 5, 5, 6, 5]
List after filteration : [4, 5, 4, 3, 3, 5, 6, 5]
```

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