# Python | K occurrence element Test

• Last Updated : 19 Feb, 2020

There are many common problems that a developer or common programmer comes across in day-day coding. One such problem is finding if an element occurs a certain number of times in list. Let’s discuss certain ways to deal with this problem.

Method #1 : Using `sum()` + list comprehension
The list comprehension can be clubbed with the sum function for achieving this particular task. The sum function does the summation part and the logical case of returning true is dealt in list comprehension part.

 `# Python3 code to demonstrate ``# K occurrence element Test``# using sum() + list comprehension`` ` `# initializing list``test_list ``=` `[``1``, ``3``, ``5``, ``5``, ``4``, ``5``]`` ` `# printing original list``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing k ``k ``=` `3`` ` `# initializing N``N ``=` `5`` ` `# using sum() + list comprehension``# K occurrence element Test ``res ``=` `0``res ``=` `sum``([``1` `for` `i ``in` `test_list ``if` `i ``=``=` `N]) ``=``=` `k``if` `res ``=``=` `1` `:``    ``res ``=` `True``else` `: ``    ``res ``=` `False``     ` `# printing result ``print` `(``"Does N occur K times ? : "` `+` `str``(res))`

Output :

```The original list is : [1, 3, 5, 5, 4, 5]
Does N occur K times ? : True
```

Method #2 : Using `next() + islice()`
These both functions can be used together to perform this particular task in more efficient manner than above. The islice function would handle the summation part and next function helps with iteration logic.

 `# Python3 code to demonstrate ``# K occurrence element Test``# using next() + islice()``from` `itertools ``import` `islice`` ` `# initializing list``test_list ``=` `[``1``, ``3``, ``5``, ``5``, ``4``, ``5``]`` ` `# printing original list``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing k ``k ``=` `3`` ` `# initializing N``N ``=` `5`` ` `# using next() + islice()``# K occurrence element Test``func ``=` `(``True` `for` `i ``in` `test_list ``if` `i ``=``=` `N)``res ``=` `next``(islice(func, k ``-` `1``, ``None``), ``False``)``     ` `# printing result ``print` `(``"Does N occur K times ? : "` `+` `str``(res))`

Output :

```The original list is : [1, 3, 5, 5, 4, 5]
Does N occur K times ? : True
```

My Personal Notes arrow_drop_up