Python Arrays Minimize Values

Question

I am trying to change the values of an array into smaller numbers like

list = [1,3,7,3] into list = [1,2,3,2]

I already have a few lines of code to keep it organized.

def sortItems(list):
    counts = collections.Counter(list)
    sortedlist = sorted(list, key=counts.get, reverse=True)
    return sortedlist

been crawling all over W3Schools and other forums but still unsure

What is the logic you want, why 7 becomes 3? Is it because it is the third biggest value? — Winson Tanputraman
– Winson Tanputraman, Commented Jan 23, 2022 at 2:53
yes. I am trying to change it so that 1 will become 1 3 will become 2 and 7 will become 3. — BaronBeef
– BaronBeef, Commented Jan 23, 2022 at 2:55
It should become ``` [3,1,2,1] ``` but the sorting function will change it to ``` [1,1,2,3] ``` — BaronBeef
– BaronBeef, Commented Jan 23, 2022 at 2:58

Raymond Kwok · Accepted Answer · 2022-01-23 03:21:52Z

3

l = [1, 3, 7, 3] 

unique_keys = set(l)

mappings = {key: val for val, key in enumerate(sorted(unique_keys), 1)}

print(list(map(mappings.get, l)))

Orders are preserved by the sorted().

edited Jan 23, 2022 at 3:21

answered Jan 23, 2022 at 2:57

Raymond Kwok

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3 Comments

Raymond Kwok Over a year ago

yes, I have changed that.

Raymond Kwok Over a year ago

oh sorry, I misunderstood. You are right! It will be better with enumerate(..., 1).

bb1 Over a year ago

Or with pandas: pd.Series(mylist).rank(method='dense').to_list()

Mateen Ulhaq · Accepted Answer · 2022-01-23 03:07:53Z

0

(This answer addresses the information in the comments.)

For a performant implementation, count, sort keys, then repeat and flatmap.

from collections import Counter
from itertools import repeat

def flatmap_repeat_sort_count(xs):
    counts = Counter(xs)
    keys = sorted(counts.keys())
    return [
        x
        for i, k in enumerate(keys, start=1)
        for x in repeat(i, counts[k])
    ]

Example runs:

>>> flatmap_repeat_sort_count([1, 3, 7, 3])
[1, 2, 2, 3]

>>> flatmap_repeat_sort_count([7, 1, 3, 1])
[1, 1, 2, 3]

answered Jan 23, 2022 at 3:07

Mateen Ulhaq

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