First creative solution for Even the Last by veky - python coding challenges

Enable Javascript in your browser and then refresh this page, for a much enhanced experience.

First solution in Creative category for Even the Last by veky

checkio=lambda a:sum(a[::2])*(len(a)and a[-1])

Feb. 20, 2014

Comments:

PHANTOM0308 on May 31, 2018, 8:17 a.m.
Thumb up for how you avoid the else-if statement when arrry is empty, but what does it exactly mean by ( a and b ) # 'and' should return a booleen type right? I see you using this sort of expression a lot, but cannot figure out the grammar 0.0

veky on May 31, 2018, 4:08 p.m.
<blockquote> ‘and’ should return a booleen type right? </blockquote> Where do you get such ideas? :-) It's as if you say `for` should return `iter`, or `except` should return `type`. :-P `and` is a control-flow protocol, not an operator. Operators cannot control evalutation of their operands, for one thing. They are usually written using symbols, not words, for another. Ok, try to write `and` as a function. Imagine you have laziness in arguments. You'll probably write something like this: <pre class='brush: python'>def and?(left, right): if left: if right: return True else: return False else: return False </pre> But look at the nested `if`. Wouldn't it make strictly more sense to just return right? You don't need its truth value at all. Of course, if right is an instance of bool, then you just get speed, but if it's instance of anything else, you get additional semantics. Just using a truth value to decide which thing you want to return doesn't mean you need to return a truth value. Study the phenomenon of "Boolean blindness" sometimes. ;-) Ok, so you have <pre class='brush: python'>def and?(left, right): if left: return right else: return False </pre> and again you have the same pattern. In the second branch, you got the left at the top of the stack already, and you know it's false. Why discard it and return a plain False, cutting its value to just one bit? Of course, same as above, you get speed if left is a bool, and additional semantics (escaping boolean blindness) if it's not. So, in fact, `left and right` is simply a shortcut for `right if left else left`, which of course doesn't have to return a bool -- at least here it is clear enough, right? :-)

bsquare on Sept. 18, 2019, 1:53 p.m.
Very smart solution!

Somebody12345678910_0eb2e11a93 on May 27, 2021, 12:37 p.m.
Wow i Love this solution!

List but not the least

0 %

You ClassRoom Demo is Ready With the new tool CheckiO ClassRoom, you will be able to analyze your students' progress, have your own leaderboard, change missions order on the map, and so on.