# Python program to test for Non-neighbours in List

• Last Updated : 02 Dec, 2020

Given teo elements, write a Python program to check that they don’t occur as their neighbours in list

Examples:

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Input : test_list = [3, 7, 2, 1, 4, 5, 7, 9], i, j = 7, 4
Output : True
Explanation : 7 doesn’t occur are 4’s neighbour.

Input : test_list = [3, 7, 2, 1, 4, 5, 7, 9], i, j = 5, 4
Output : False
Explanation : 5 occurs are 4’s neighbour.

Method #1 : Using loop

In this, we check for next and previous elements to not be i or j while iteration of list.

## Python3

 `# Python3 code to demonstrate working of``# Test for Non-neighbours in List``# Using loop`` ` `# initializing list``test_list ``=` `[``3``, ``7``, ``2``, ``1``, ``4``, ``5``, ``7``, ``9``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing i, j``i, j ``=` `7``, ``4`` ` `res ``=` `True``for` `idx ``in` `range``(``1``, ``len``(test_list) ``-` `1``):``    ``if` `test_list[idx] ``=``=` `i:`` ` `        ``# check for surrounding element to be j if i``        ``if` `test_list[idx ``-` `1``] ``=``=` `j ``or` `test_list[idx ``+` `1``] ``=``=` `j:``            ``res ``=` `False``            ``break`` ` `# printing result``print``(``"Are i, j Non-neighbours' : "` `+` `str``(res))`
Output
```The original list is : [3, 7, 2, 1, 4, 5, 7, 9]
Are i, j Non-neighbours' : True```

Method #2 : Using all()

This is one liner approach to solve this problem. In this, we perform task of checking for all elements for neighbours using all() in generator expression in all().

## Python3

 `# Python3 code to demonstrate working of``# Test for Non-neighbours in List``# Using all()`` ` `# initializing list``test_list ``=` `[``3``, ``7``, ``2``, ``1``, ``4``, ``5``, ``7``, ``9``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing i, j``i, j ``=` `7``, ``4`` ` `# checking for preceding and succeeding element ``# not to be j if curr is i``res ``=` `all``(test_list[idx ``-` `1``] !``=` `j ``and` `test_list[idx ``+` `1``] !``=``          ``j ``for` `idx ``in` `range``(``1``, ``len``(test_list) ``-` `1``) ``if` `test_list[idx] ``=``=` `i)`` ` `# printing result``print``(``"Are i, j Non-neighbours' : "` `+` `str``(res))`
Output
```The original list is : [3, 7, 2, 1, 4, 5, 7, 9]
Are i, j Non-neighbours' : True```

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