[Solved] Python, append() and NoneType, no slice: is there a hack around it, if there is which is preferred(append or +)?

Question

I tried to use append() on a list only to realize I couldn't slice it because it was none type. I thought append only altered the list content.
I am bewildered by what I did wrong because I wasn't able to print it even, after appending it.

So I did a search, saw on StackOverflow that list + list was better, kept the list pure and all.

Is that really a general statement of truth? What are your opinions on it?
When do you refrain from using +, I mean, is there a situation where append is better? I might need to review my previous assignments depending on what you say.

Thank you.

I was doing a base conversion exercise. Here you can see how I had to use +. I cannot even tell if I forgot doing something with append that I used to do in my earlier exercises.
I could also use some advice on concise and precise commenting. I suck at it.
https://code.sololearn.com/c9l8zpAzr0VE/?ref=app

Answer 1

Korkunç TheTerrible ,

here is a test about the execution time of various ways to add elements to a list:
https://code.sololearn.com/cxU4i0oZOitk/?ref=app

Answer 2

Korkunç TheTerrible ,

the dec_to_bin() function does not return the correct bin string. see your code slightly modified:
(to check if your code is working properly, you can use the built-in function bin(...), which expects an integer value and returns the binary string)

https://code.sololearn.com/cmgPq9A1F61v/?ref=app

Answer 3

Lothar

Hi, thank you for the reply:

- so with each iteration I insert str(r) number at index 0, right? That's great, thank you. I had tried to get rid of slicing because of one of your posts about that earlier yet in another exercise of mine, this answers that too.

<nonsense> This place had nonsense in it because my eyes failed to see things that they should have, sparing other newbies not to cause confusion. </nonsense>

Answer 4

BTW, if you have time, what about a comparison between + and append() and in what situations append() is preferred wrt to "+", if ever?

That's my original question, this code is just an example to how I had to use an operator rather than a method.

Kind of makes sense. What I don't understand is why methods return None, when I'm printing an object using the method on it. Why isn't it the same object, only altered?

I need to keep rereading things I guess.

Answer 5

Lothar I was wrong, the code works so I deleted my post. My number was 2517 not 2157. Sorry for that. (one of the causes of the nonsense)

<nonsense>Still though, what I did earlier works. So because I got lucky here, I don't understand what the warning is. (if a newbie's reading this: this paragraph, too, is nonsense, due to misreading something twice since my first testing) </nonsense>

I will study your code, I feel I took enough of your time. Thanks a lot, btw :-)

Answer 6

Lothar I apologize for pinging your name many times, I understand it all now.

Thank you so much.

I wasn't lucky, I was blind. I didn't realize the test number gave the wrong result(lol I managed to not see it during my recheck)

I will keep this question as unsolved, I wonder what people have to say about the title question

BUT

thank you, and please don't hate me for @'ting so frequently.

I hate it when I recheck and misread something again. I'll do more checks.

Answer 7

Today is my swoosh day.

Now what I'm wondering is how come the x = x // 2 followed by r = x % 2 didn't reduce the number of operations by half, skipping every other remainder not once, but always.

I am also afraid of committing another blindness with supposedly functional eyes. (I think it's rather my brain that skips things that are in order, inadverently, some dyslexia sort of thing)

I don't want to annoy all these lovely people who help us noobs so much, so I will not ask more about this to anyone.

I will rest a little and examine it until I understand why my code doesn't fail even more.

And I am overstating, yes, but if anyone sees this, I really want to know, as stated in my title question, where append alters a list more favorably thab the plus operator does. Why append is used at all.
Sorry to all my noobmates for any confusion I might have caused. This sort of compulsion is bad, I know.