re-opened there as a more generic suggestion since all languages are affected

WIoHu, if you're going to critique something because it's 'not good for beginners', your explanation should meet a basic level of quality, your tone should have a modicum of respectfulness to it, and I SHOULD BE ABLE TO UNDERSTAND THE ISSUE AS A BEGINNER.
I know I'm years and years after the fact, but this crap just made me feel bad about what I learned (on my own, not from this person's solution).
If you really cared about beginners, you would 1) use language that was easy for beginners to understand, and focus more on explaining exactly where and why the other person's code is 'bad', 2) approach it with a clear intent to educate and not denegrate, and 3) when you had to clarify something, take the time to disambiguate the good solution vs the bad solution.
Otherwise you're not doing it to help beginners. You're doing it to feel a sense of superiority over others because you've learned something they haven't yet.
It's bloodsport.

push is specified correctly, after that's, it's just a name. "push" is not even the only misname in there. but I don't think any of this is going to be changed now.

Closing.

but you want it to last longer :)

Personally, I believe that the .union(arr2) is incredibly useful here. Wish you nothing but the best. hugs and kisses xox

I feel like the intent of katas like these are to challenge us NOT to rely on built-ins and really think about how to replicate the behavior of the built-in method. shrug

Agree

Please stop arguing guys. All those solutions are bad, yours and mine too. We parse twice the array while it would be so easy with only one pass.

@WloHu list comprehension is an important thing to learn for python newbies. And your solution actualy IS shit

How can you check the speed?

isslice returns a generator, so I think he/she is just trying to avoid creating a whole second array starting at index 1 for zip. Its a small optimization but pretty cool.

lol