Search through nested list, find sub-element and remove based on value

Question

I have a nested list

test_list = [['AA', 'OFF'], ['BB', 'OFF'], ['BB', 'ON'], ['BB', 'ON'], ['CC', 'OFF'], ['DD', 'OFF'], ['EE', 'OFF']]

I would like to find matching index 0 sub-elements such as

['BB', 'OFF'], ['BB', 'ON'], ['BB', 'ON']

and filter out any sub-items with 'OFF' in index 1 as long as there is a matching index 0 with ' ON' found and not keep duplicates, otherwise just keep the sub-elements.

So for the above example, the end result would be:

[['AA', 'OFF'], ['BB', 'ON'], ['CC', 'OFF'], ['DD', 'OFF'], ['EE', 'OFF']]

I tried converting the above to a dictionary but the result changes depending on the chronological order of the list:

test_dict = dict(test_list)
test_dict

output:

{'AA': 'OFF', 'BB': 'ON', 'CC': 'OFF', 'DD': 'OFF', 'EE': 'OFF'}

Which is exactly what I want

BUT for

test_list1 = [['AA', 'OFF'],['BB', 'ON'],['BB', 'OFF'],['CC', 'OFF'],['DD', 'OFF'],['EE', 'OFF']]
test_dict1 = dict(test_list1)

test_dict1
{'AA': 'OFF', 'BB': 'OFF', 'CC': 'OFF', 'DD': 'OFF', 'EE': 'OFF'}

Which neglects ['BB', 'ON'] because of its position and is not fitting to what I want.

The order of the test_table list doesn't really matter as long as the end values are unique and meet the 'ON' / 'OFF' criteria above. I guess I am looking for a way to group and sort the nested list so that I can then turn it into a dictionary and output the desired result?

what happens when you have two OFF and one ON like this ['BB', 'OFF'], ['BB', 'OFF'], ['BB', 'ON'],, would you want ON or OFF ? — Joe Ferndz
– Joe Ferndz, Commented Jan 25, 2021 at 6:15
If ON is in the list then it has to be the one displayed and OFF should be dropped. — slider8p
– slider8p, Commented Jan 25, 2021 at 7:51

David Buck · Accepted Answer · 2021-01-25 06:08:02Z

2

You can simply sort the list on the second element of the sub-lists, so that ON always follows OFF with the code:

test_list1 = [['AA', 'OFF'],['BB', 'ON'],['BB', 'OFF'],['CC', 'OFF'],['DD', 'OFF'],['EE', 'OFF']]
test_dict1 = dict(sorted(test_list1, key=lambda x: x[1]))

Results in test_dict1 containing:

{'AA': 'OFF', 'BB': 'ON', 'CC': 'OFF', 'DD': 'OFF', 'EE': 'OFF'}

answered Jan 25, 2021 at 6:08

David Buck

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