Python remove elements from a list that contains substrings from other list

Question

I have two lists, and I want to remove the elements on a list l1 that have any different substring not mentioned in l2. My lists are the following:

l1 = ['PC||macOS||Xbox One||PlayStation 4||Nintendo Switch',
 'macOS||PC||Xbox One',
 'iOS',
 'PC||PlayStation 4',
 'PC',
 'Web',
 'PC||macOS',
 'PC||macOS||Linux',
 'PC||Linux',
 'PC||Web',
 'PC||Xbox One||PlayStation 4||Nintendo Switch',
 'PC||macOS||Linux||Web',
 'macOS||PC||Linux||PlayStation 4||Xbox One',
 'PC||Android',
 'PC||macOS||Linux||Android',
 'macOS||iOS||Linux||PC||PlayStation 4',
 'Linux',
 'PC||macOS||Web',
 nan,
 'Xbox One||PC||Nintendo Switch||PlayStation 4',
 'iOS||PC||macOS||Linux',
 'PC||macOS||Android||Web',
 'iOS||Linux||PC||macOS',
 'Android',
 'macOS||PC||Linux',
 'Linux||PC'
]

l2 = ['PC', 'macOS', 'Linux', 'mac', 'Web']

What I want to obtain is all combinations in l1 that ONLY have the substrings stated in l2. Therefore, in the new list I won't have any element with words like "Playstation 4" or "iOS" or "Xbox One". Something like:

l3 = [
 'PC',
 'Web',
 'PC||macOS',
 'PC||macOS||Linux',
 'PC||Linux',
 'PC||Web',
 'PC||macOS||Linux||Web',
 'PC||macOS||Linux||Android',
 'Linux',
 'PC||macOS||Web',
 'macOS||PC||Linux',
 'Linux||PC'
]

what have you done so far? also may I ask if you are familiar with regular expressions? cause I think it will do the job :D — Ice Bear, Dec 16 '20 at 15:36
I've tried with nested for loops and 'str.contains()' and adapting this https://stackoverflow.com/questions/4211209/remove-all-the-elements-that-occur-in-one-list-from-another but with no result — marsolmos, Dec 16 '20 at 15:40
Loop over the items in list1. For each item, split it on `||` and do a nested loop on the split items, comparing each one to the items in list2. If you get to the end of the nested loop without finding any matches, append the item to list3. — John Gordon, Dec 16 '20 at 15:45

score 3 · Accepted Answer · answered Dec 16 '20 at 15:36

3

Make l2 a set for fast lookup then use all with a generator comprehension:

l2_set = set(l2)
l3 = [x for x in l1 if all(chunk in l2_set for chunk in x.split("||"))]

answered Dec 16 '20 at 15:36

Aplet123

33,825
1
29
55

1

pretty much I was also targeting for, a bit of explanation might help with the cryptic code. – Pedro Rodrigues Dec 16 '20 at 15:37

score 3 · Answer 2 · answered Dec 16 '20 at 15:36

3

using sets is pretty easy.

l3 = [v for v in l1 if set(v.split('||')) <= set(l2)]

gonna have to filter out that errant nan though...

answered Dec 16 '20 at 15:36

acushner

9,595
1
34
34

1

This one also works perfectly, but Aplet123 answered before, so I chose his answer as the final one. Thanks a lot @acushner – marsolmos Dec 16 '20 at 15:43
no offense here, glad you got some good answers! – acushner Dec 16 '20 at 17:22

Python remove elements from a list that contains substrings from other list

2 Answers2