Insert element in Python list after every nth element

I’ve got two one liners. Given: >>> letters = [‘a’,’b’,’c’,’d’,’e’,’f’,’g’,’h’,’i’,’j’] Use enumerate to get index, add ‘x’ every 3rd letter, eg: mod(n, 3) == 2, then concatenate into string and list() it. >>> list(”.join(l + ‘x’ * (n % 3 == 2) for n, l in enumerate(letters))) [‘a’, ‘b’, ‘c’, ‘x’, ‘d’, ‘e’, ‘f’, ‘x’, … Read more

How to remove all element from array except the first one in javascript

You can set the length property of the array. var input = [‘a’,’b’,’c’,’d’,’e’,’f’]; input.length = 1; console.log(input); OR, Use splice(startIndex) method var input = [‘a’,’b’,’c’,’d’,’e’,’f’]; input.splice(1); console.log(input); OR use Array.slice method var input = [‘a’,’b’,’c’,’d’,’e’,’f’]; var output = input.slice(0, 1) // 0-startIndex, 1 – endIndex console.log(output);

Difference between list, sequence and slice in Python?

You’re mixing very different things in your question, so I’ll just answer a different question You are now asking about one of the most important interface in Python: iterable – it’s basically anything you can use like for elem in iterable. iterable has three descendants: sequence, generator and mapping. A sequence is a iterable with … Read more

Understanding string reversal via slicing

Sure, the [::] is the extended slice operator. It allows you to take substrings. Basically, it works by specifying which elements you want as [begin:end:step], and it works for all sequences. Two neat things about it: You can omit one or more of the elements and it does “the right thing” Negative numbers for begin, … Read more

Iteration over list slices

If you want to divide a list into slices you can use this trick: list_of_slices = zip(*(iter(the_list),) * slice_size) For example >>> zip(*(iter(range(10)),) * 3) [(0, 1, 2), (3, 4, 5), (6, 7, 8)] If the number of items is not dividable by the slice size and you want to pad the list with None … Read more