from itertools import not compress clear solution for Compress List by veky - python coding challenges

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from itertools import not compress solution in Clear category for Compress List by veky

from itertools import groupby

def compress(items):
    for key, _ in groupby(items): yield key

Jan. 11, 2020

Comments:

piter239 on May 17, 2020, 2:20 p.m.
nice!

Striga on Dec. 2, 2020, 3:21 p.m.
I like the use of yield and overall how short the code is.

veky on Dec. 3, 2020, 6:19 a.m.
It's just a first projection of itertools.groupby. :-)

digant on Nov. 22, 2021, 9:48 a.m.
Hi, I have a question. Doesn't yield pause the function. how did it return the whole list ??

veky on Nov. 22, 2021, 9:49 a.m.
It didn't, but it didn't have to. Read the task. Output can be an iterator. :-)

dubi95 on July 29, 2021, 5:48 p.m.
Awesome solution, good to know of that groupby :)

veky on July 30, 2021, 1:20 p.m.
You can learn about these things either through reading the Python stdlib documentation, or reading my solutions. :-D

tssrkt777 on Dec. 6, 2021, 2:08 a.m.
Very nice solution. :) So minimalistic!!! I like it very much.) Keep doing it.)

hbczmxy on Dec. 31, 2021, 11:48 a.m.
Compared with your solution, mine looks clumsy. It is great to think of using itertools.groupby as a solution. But I feel that if you use list comprehension, the result will be more concise and faster. <pre class='brush: python'>import itertools compress = lambda items: [key for key, _ in itertools.groupby(items)] </pre>

veky on Dec. 31, 2021, 11:50 a.m.
Concise is subjective. To me, what I wrote above is more concise. :-) Faster would surprise me very much. Your solution has to do everything my solution does, plus create a list. [Not to mention that mine works with infinite `items`.]

hbczmxy on Dec. 31, 2021, 12:09 p.m.
In front of you, my knowledge is still too little! I need to learn more! If you offend, please forgive me, sorry

hbczmxy on Dec. 31, 2021, 12:34 p.m.
As a python novice, I am still a little confused. I want to ask you two questions, which are also my doubts. <ul> <li>Why is using list comprehension not faster than generator function?</li> <li>Why is the use of list comprehension not suitable for all situations?</li> </ul> If you have time, please help me to solve my puzzles! Thanks a lot!

hbczmxy on Dec. 31, 2021, 12:36 p.m.
As a Python novice, I still have some doubts. I want to ask you two questions, which are also my doubts. <ul> <li>Why is it not faster to use a list comprehension than a generator function?</li> <li>Why is the use of list comprehension not suitable for all situations?</li> </ul> If you have time, please help me to solve my puzzles! Thanks a lot!

veky on Dec. 31, 2021, 9:30 p.m.
<blockquote> Why is it not faster to use a list comprehension than a generator function? </blockquote> I think I explained that. List comprehension also has to generate all the elements (it also does that in a separate frame, much like the ordinary function), but afterwards it has to combine them into a list. I'd really like to know why you think it would be faster, as if there's something a generator would have to do and list comprehension wouldn't (what?). <blockquote> Why is the use of list comprehension not suitable for all situations? </blockquote> For the same reason nothing is suitable for all situations: the world is complicated. ;-) For example, as I wrote above, my solution works when `items` is infinite, while yours doesn't. <pre class='brush: python'>>>> for digit in compress(oct(n)[2] for n in itertools.count()): digit </pre> <blockquote> If you offend, please forgive me, sorry </blockquote> If I were offended by honest questions, I'd have left CiO a long time ago. :-D

viktor.chyrkin on Jan. 8, 2022, 8:44 p.m.
You are the best with itertools.

veky on Jan. 8, 2022, 9:11 p.m.
Of course <a href="https://py.checkio.org/mission/tree-walker/publications/veky/python-3/everybody-loves-raymond/share/83684ae45b70cd0093a8fa6c050465be/">Raymond</a> is the best. :-D [He's the original author of itertools.]

Selindian on March 22, 2022, 11:04 p.m.
Really nice. Had to try and puzzle a bit to understand it, as I never have used groupby() before. Thank you for your solution. :-)

veky on March 23, 2022, 2:19 a.m.
You're welcome. :-)

U.V on June 6, 2022, 1:27 p.m.
Wery compact and effective solution

Sinv on June 21, 2022, 12:45 p.m.
Fabulous! Briefly and clearly! I like this way.

H0r4c3 on July 16, 2022, 8:36 p.m.
Nice and clear! A very good idea was the use of groupby together with yield!

veky on July 17, 2022, 4:56 a.m.
Groupby is the real solution, yield is just a method of reporting it.

Wartem on Aug. 11, 2022, 11:33 a.m.
Really great solution. Making it short yet still readable and clear is like creating art.

veky on Aug. 12, 2022, 4:24 p.m.
I've been called a Python poet before. ;-)

jv43 on March 1, 2023, 3:50 a.m.
Nice and clear! A very good idea was the use of groupby together with yield!

veky on March 2, 2023, 3:14 a.m.
yield is just an artefact of the solving system. Groupby is the real hero here. :-)

Germ on May 2, 2023, 9:22 a.m.
I didn't know about groupby, i have to say that really helps.

StefanPochmann on May 3, 2023, 1:26 p.m.
Inspired me to do it with it, here's one version: ``` def compress(items): from itertools import compress, tee, chain, starmap, pairwise from operator import ne a, b = tee(items) return compress(a, chain([True], starmap(ne, pairwise(b)))) ``` Another: ``` def compress(items): from itertools import compress, tee, chain, starmap, pairwise, islice from operator import ne a, b = tee(items) return chain(islice(a, 1), compress(a, starmap(ne, pairwise(b)))) ``` Or with groupby: ``` def compress(items): from itertools import compress, groupby return items and compress(zip(groupby(items))) ``` But that feels like cheating, and it's strictly worse than `return next(zip(*groupby(items)), [])`.

StefanPochmann on May 3, 2023, 1:38 p.m.
Oh I just realized I don't need `tee`, as the input is definitely a list. I guess it's my habit of thinking in iterators...

veky on May 4, 2023, 11:37 a.m.
:-D Thanks for the laugh. :-)

Pavellver on June 19, 2023, 7:34 p.m.
Nice solution. It is short, but readable and clear.

veky on June 21, 2023, 3:30 a.m.
My solutions usually are, despite first impressions to the contrary. :-]

lbe on Aug. 21, 2023, 8:27 p.m.
I never would have thought of that!!

veky on Aug. 22, 2023, 12:40 a.m.
that's the main reason I wrote it. :-D

yufengyuyun on Oct. 10, 2023, 2:10 p.m.
I know a new method from your solution. Nice!

mennadiego on Oct. 15, 2023, 4:40 p.m.
yield keyword like a boss here, very small code. Like it!

Magu on Oct. 21, 2023, 3:47 p.m.
i think it's a really elegant solution. very intelligent and simple. :D

U.V on Aug. 9, 2024, 3:14 p.m.
Interesting using of yield + groupby

Orthomonalus on Oct. 28, 2024, 1:14 p.m.
very good. using groupby effectively removes consecutive duplicates from the input iterable items.

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