Descending order unique squares

Descending order unique squares - Printable Version

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Descending order unique squares - OmegaRed94 - Sep-26-2021

Good day, Dear Pythonistas

I have the following problem: Given a list, we should write a function that returns sorted in descending order unique squares of numbers contained in this list

I have got the solution in the following way, it works correctly:

def squares_list(l):
    for elem in l:
        empty_list.extend(elem)
    new_list=list(set(empty_list))
    new_list.sort(reverse=True)
    squares=[i**2 for i in new_list]
    return squares
print(squares_list([[1, 2], [3], [4], [3, 1]]))

Could you, please, suggest, how I could write this code or the solution in the shortest possible optimal way (a smaller number of characters)?

RE: Descending order unique squares - deanhystad - Sep-26-2021

Search for a short way to flatten the list. Maybe itertools.chain?

Do not use variables to save intermediate results. Chain operations together using return values

    return [i**2 for i in new_list]
    # instead of
    squares=[i**2 for i in new_list]
    return squares

Use sorted instead of sort.

sorted_unique_list=sorted(set(unsorted_list))

I can write your function as a 1 liner, and I didn't have to be clever. For a one liner it doesn't look too bad

RE: Descending order unique squares - OmegaRed94 - Sep-26-2021

Thank you very much) By now it looks like this:

import itertools
def process(l):
    return [i**2 for i in sorted(set(list(itertools.chain(*l))))[::-1]]

RE: Descending order unique squares - ndc85430 - Sep-26-2021

Why do you need the call to list there?

RE: Descending order unique squares - deanhystad - Sep-26-2021

Leave out the list() call. Not needed. Have sorted reverse the order

RE: Descending order unique squares - OmegaRed94 - Sep-26-2021

(Sep-26-2021, 09:00 AM)deanhystad Wrote: Leave out the list() call. Not needed. Have sorted reverse the order

Thanks again

RE: Descending order unique squares - ndc85430 - Sep-26-2021

If the nesting of all the function calls bothers you, you can probably flatten it out with thread_first or thread_last from the third-party Toolz library.