__getitem__ clear solution for Best Stock by flpo - python coding challenges

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__getitem__ solution in Clear category for Best Stock by flpo

def best_stock(data):
    return max(data, key=data.__getitem__)

Nov. 25, 2017

Comments:

zstarzz on Jan. 30, 2018, 10:17 p.m.
Absolutely amazing. My solution ended up being over 10 lines.

flpo on Jan. 30, 2018, 10:32 p.m.
Thanks!

defendeerofjustice on April 1, 2018, 5:07 p.m.
Can anyone explain how getitem works, please?)

flpo on May 19, 2018, 8:46 a.m.
Sure, who better than the documentation? :) ... This is Python’s approach to operator overloading, allowing classes to define their own behavior with respect to language operators. For instance, if a class defines a method named `getitem()`, and `x` is an instance of this class, then `x[i]` is roughly equivalent to `type(x).getitem(x, i)` ... source: <a href="https://docs.python.org/3/reference/datamodel.html">https://docs.python.org/3/reference/datamodel.html</a>#special-method-names see also: <a href="https://docs.python.org/3/reference/datamodel.html#object.__getitem__"><a href="https://docs.python.org/3/reference/datamodel.html">https://docs.python.org/3/reference/datamodel.html</a>#object.getitem</a>

jsayle_8b7480d368a348f084b5ad5 on May 10, 2018, 7:27 p.m.
Nice! I thought using max() would lead to a straightforward solution, but couldn't wrap my head around how to implement. Very clear and like the use of getitem

flpo on May 19, 2018, 8:40 a.m.
Thanks!

ohtok on May 16, 2018, 6:42 a.m.
hello,Could you tell me why " return sorted(data,key=lambda x:x[1],reverse=True)[0] " doesn't work for the second test?thx!

LKJlove on May 19, 2018, 8:19 a.m.
return sorted(data.items,key=lambda x:x[1],reverse=true)[0]

flpo on May 19, 2018, 8:23 a.m.
Hi, did you try your code? <pre class='brush: python'>TypeError: 'builtin_function_or_method' object is not iterable </pre> `dict.items` is a method: <pre class='brush: python'>return sorted(data.items(),key=lambda x:x[1],reverse=True)[0] ^^ </pre> and don't forget to extract the key only from the returned key/value pair ;) <pre class='brush: python'>return sorted(data.items(),key=lambda x:x[1],reverse=True)[0][0] ^^^ </pre>

LKJlove on May 19, 2018, 9:08 a.m.
Actually I didn't try it although I was not sure before.I've got it now from your reply.Thx!

flpo on May 19, 2018, 8:39 a.m.
Hi, it doesn't work because an iteration over dict object does not gives you the sequence of pair (key/value) but only the sequence of keys, so your `key` function `lambda x:x[1]` takes the second char of the dict key instead of the value. In order to iterate the pair key/value you should call the method `dict.items()`: <pre class='brush: python'>return sorted(data.items(),key=lambda x:x[1],reverse=True)[0][0] </pre> The last added `[0]` is needed in order to extract the key only from the returned key/value pair Note also that, generally, if you need the maximum element from a sequence it is better (more efficient, and in my opinion also more readable) to get only the `max(...)` instead of `sorted(..., reverse=True)[0]` <pre class='brush: python'>return max(data.items(),key=lambda x:x[1])[0] </pre>

ohtok on June 28, 2018, 12:31 a.m.
thanks a lot! have a nice day:)

Leetroch on May 29, 2018, 3:49 p.m.
It's awesome. But I have to take some time to understand getitem.

goukun07 on Sept. 4, 2018, 4:03 p.m.
So clear, I like it.

hbxz on Sept. 11, 2018, 11:52 a.m.
Really clear. Thanks.

lpotahina on Sept. 24, 2018, 2:55 p.m.
"data.get" could be used instead of "data.getitem"

My3bka on Oct. 24, 2018, 6:45 a.m.
yes, i mean it's clearly: return max(data, key=data.get)

flpo on Sept. 25, 2019, 5:23 p.m.
Sorry, I don't agree :-) I would say that `dict.get` is clearer then `dict.getitem` only for those who don't know `getitem` semantic.

zasz on Dec. 29, 2018, 8:03 p.m.
amazing solution, but i think it's out of the scope of a novice like me.

Idletuner on Jan. 15, 2019, 7:30 p.m.
Amazing, I still have a lot to learn ...

Fodere on Feb. 11, 2019, 4:24 a.m.
Short and efficient, good job!

caitlin11 on April 23, 2019, 9:28 a.m.
:)

massif1 on May 29, 2019, 9:30 p.m.
To be honest, I try to solve these missions to get to know how it is done properly by checking the solutions. How little did I know what's possible. Thanks for sharing awesomeness!

papaguita on July 18, 2019, 8:53 p.m.
you don't need getitem) -----> key=data.get) is enough

flpo on Sept. 25, 2019, 5:21 p.m.
So, what is your interpretation of "is enough"? Are you talking about the number of chars comprised in the method name? If so, then I agree with you, since `len("get") < len("getitem")` :) But, unless the goal is golfing, when I call a method I would care more of its semantic, rather than the length of its name :) That said, let's have a look at the doc to figure out the semantic differences among `dict.get` and `dict.getitem`: <pre class='brush: python'>>>> help(dict.__getitem__) x.__getitem__(y) <==> x[y] >>> help(dict.get) D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None </pre> So, not surprisingly (for those who know `getitem` semantic), `d.getitem(k)` is equivalent to `d[k]`, and `d.get(k)` is equivalent to `d.getitem(k)` if `d` contains `k` and to `None` otherwise. I would claim that `dict.get` is a protected version of `d.getitem` which returns a placeholder value instead of raising an exception if the dict does not contain the given key. With that in mind, I would (informally) say that `dict.get` is somehow more than `dict.getitem`. Then, I would change your claim as: I don't need `get` ----> `getitem` is enough :). The reason is: here we are iterating over the dict keys using `max`, so we don't need a protected version of `getitem` which guards against key missing, as we are sure that all the keys are there. Last but not least, publishing a solution has also (mainly) teaching purposes, this solution suggests to have a look at what is `getitem` to those who never met him :)

belfiore on Aug. 24, 2019, 10:58 p.m.
Can sombody please walk me through this line of code step by step and argument by argument? I dont get it :/

asp.anthony1 on Sept. 18, 2019, 10:48 a.m.
so i played around with this and found something strange, maybe some one an help explain this to me: a = {'test': 23, 'world': 54, 'hello': 43} print(max(a)) <h1>it prints out world, great</h1> a = {'CAC': 10.0,'ATX': 390.2,'WIG': 1.2} print(max(a)) <h1>it prints our WIG</h1> I'm not sure why it works for one and not the other, is it the float values or perhaps some value of the key strings?

LarceFox on Sept. 25, 2019, 9:42 a.m.
Hi, it happens because you seek maximum from 'a' keys (it compares strings). If you need to compare values type this 'a.values()' as argument of 'max' function.

tumaowolf on Jan. 3, 2020, 7:52 a.m.
Amazing...

mAzrunnr on Nov. 13, 2021, 3:48 p.m.
This is such a simple code. Thanks for idea

Look up in the Dict()

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