# Python | Interval Initialization in list

There are numerous ways to initialize the list with the elements, but sometimes, its required to initialize the lists with the numbers in a sliced way. This can be custom and hence knowledge of this can come handy. Let’s discuss certain ways in which this can be done.

Method #1 : Using `list comprehension + enumerate()`
The list comprehension can do the possible iteration part and enumerate can help in the part of logic and checking for the valid elements required in the list.

 `# Python3 code to demonstrate  ` `# interval initializing in list  ` `# using list comprehension + enumerate() ` ` `  `# initializing lists ` `test_list ``=` `list``(``range``(``50``)) ` ` `  `# printing original list ` `print` `(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# interval elements ` `N ``=` `5` ` `  `# interval difference ` `K ``=` `15` ` `  `# using list comprehension + enumerate() ` `# interval initializing in list  ` `res ``=`  `[i ``for` `j, i ``in` `enumerate``(test_list) ``if` `j ``%` `K < N ] ` `     `  `# printing result  ` `print` `(``"The modified initialized list : "` `+`  `str``(res)) `

Output :

The original list is : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49]
The modified initialized list : [0, 1, 2, 3, 4, 15, 16, 17, 18, 19, 30, 31, 32, 33, 34, 45, 46, 47, 48, 49]

Method #2 : Using `itertools.compress() + itertools.cycle()`
The above two function can combine to facilitate the solution of the discussed problem. The cycle function can to the task of repetition and the compress function can be beneficial when it comes to clubbing the segments together.

 `# Python3 code to demonstrate  ` `# interval initializing in list  ` `# using itertools.compress() + itertools.cycle() ` `from` `itertools ``import` `compress, cycle  ` ` `  `# initializing lists ` `test_list ``=` `list``(``range``(``50``)) ` ` `  `# printing original list ` `print` `(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# interval elements ` `N ``=` `5` ` `  `# interval difference ` `K ``=` `15` ` `  `# using itertools.compress() + itertools.cycle() ` `# interval initializing in list  ` `func ``=` `cycle([``True``] ``*` `N ``+` `[``False``] ``*` `(K ``-` `N)) ` `res ``=` `list``(compress(test_list, func)) ` `     `  `# printing result  ` `print` `(``"The modified initialized list : "` `+`  `str``(res)) `

Output :

The original list is : [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49]
The modified initialized list : [0, 1, 2, 3, 4, 15, 16, 17, 18, 19, 30, 31, 32, 33, 34, 45, 46, 47, 48, 49]

My Personal Notes arrow_drop_up Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.

Article Tags :
Practice Tags :

Be the First to upvote.

Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.