Sort list elements based on two dictionaries

Question

I was trying to sort the following list :

L = ['Z3', 'X3','V3','M0' ..., 'F2']

Based on the rules, I defined in the 2 following dictionaries:

dicMonths = {'F':1,'G':2,'H':3,'J':4,'K':5,'M':6,'N':7,'Q':8,'U':9,'V':10,'X':11,'Z':12}
dicYears = {'2':2022, '1':2021, '0':2020, '9':2019, '8':2018, '7':2017, '6':2016, '5':2015, '4':2014, '3':2013}

I applied the following code, but it doesn't work :

aa = [(elt[0], elt[1]) for elt in L]
sorted(aa, key= lambda x,y : (dicMonths[x], dicYears[y]))

It gives me the following error :

TypeError: () missing 1 required positional argument: 'y'

I want it to give me the sorted list as bellow :

['F3', 'G3', 'H3', 'J3', 'K3', 'M3', 'N3', 'Q3', 'U3', 'V3', 'X3', 'Z3', 'F4', ...]

How can I resolve this problem?

dupe https://stackoverflow.com/questions/4233476/sort-a-list-by-multiple-attributes — timgeb, Sep 24 '21 at 11:54
You are missing the key `3` in `dicYears`. Please include reproducible code in your question not pseudo code (with '...') and your expected output. — Michael Szczesny, Sep 24 '21 at 11:58
Use one of these: https://stackoverflow.com/questions/21892989/what-is-the-good-python3-equivalent-for-auto-tuple-unpacking-in-lambda — mkrieger1, Sep 24 '21 at 12:03

score 0 · Answer 1 · answered Sep 24 '21 at 12:02

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You provided an incompatible function for the key argument. key takes a function that accepts one argument and returns another. If you want this to work, you need to access the tuple argument as a single value.

Also, you don't need to split L as a separate step. Try this:

sorted(L, key=lambda l: (dicMonths[l[0]], dicYears[l[1]]))

answered Sep 24 '21 at 12:02

flakes

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Thank you, your suggestion works well. – Khadija Sep 24 '21 at 12:11
@MichaelSzczesny but I think you can upvote it – Khadija Sep 24 '21 at 12:12

score 0 · Accepted Answer · answered Sep 24 '21 at 15:34

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The suggestion from @flakes is very elegant, but probably does not produce the required output, because it gives month precedence over years. However, according to the desired output mentioned in the question, years should have precedence over months - e.g. 'Z3' < 'F4'.

That can be achieved with a slight adaption:

sorted(L, key=lambda l: (dicYears[l[1]], dicMonths[l[0]]))

answered Sep 24 '21 at 15:34

buertho

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yes, you're right I recognized it when he posted the suggestion but forgot to mention it in the comment, thanks – Khadija Sep 24 '21 at 16:34

Sort list elements based on two dictionaries

2 Answers2