Delete substrings from a list of strings

Question

I have a list

l = ['abc', 'abcdef', 'def', 'defdef', 'polopolo']

I'm trying to delete strings whose superstring is already in the list. In this case, the result should be:

['abcdef', 'defdef', 'polopolo']

I have written the code:

l=['abc','abcdef','def','defdef','polopolo']
res=['abc','abcdef','def','defdef','polopolo']
for each in l:
    l1=[x for x in l if x!=each]
    for other in l1:
        if each in other:
            res.remove(each)

but it doesnt seem to work. I have read that we cannot remove from the list while iterating over it. Hence the copy res, while l is my original list.

Your code would have worked if you broke out of the loop immediately after res.remove(each) :) For an efficient way to do this, please check my answer :) — thefourtheye
– thefourtheye, Commented Mar 6, 2014 at 11:29
pretty stupid mistake on my part now that you have explained it. :) Thank you — user2058724
– user2058724, Commented Mar 6, 2014 at 12:44

Community · Accepted Answer · 2017-05-23 11:49:45Z

9

l=['abc','abcdef','def','defdef','polopolo']
print [j for i, j in enumerate(l) if all(j not in k for k in l[i + 1:])]
# ['abcdef', 'defdef', 'polopolo']

We can speed it up a very little, by sorting the list before

l = sorted(l, key = len)
print [j for i, j in enumerate(l) if all(j not in k for k in l[i + 1:])]

As @Ashwini Chaudhary mentions in the comments, if you want to retain the duplicate strings, then you can do this

l = ['abc','defghi' 'abcdef','def','defdef','defdef', 'polopolo']
l = sorted(l, key = len)
print [j for i,j in enumerate(l) if all(j == k or (j not in k) for k in l[i+1:])]
# ['defdef', 'defdef', 'polopolo', 'defghiabcdef']

edited May 23, 2017 at 11:49

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answered Mar 6, 2014 at 10:39

thefourtheye

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9 Comments

Ashwini Chaudhary Over a year ago

Try with ['abc','defghi' 'abcdef','def','defdef','defdef', 'polopolo']

thefourtheye Over a year ago

@AshwiniChaudhary I get ['defghiabcdef', 'defdef', 'polopolo']. Is that wrong?

Ashwini Chaudhary Over a year ago

Duh! missed , after 'defghi', BTW 'defdef' count decreased to 1.

thefourtheye Over a year ago

@AshwiniChaudhary Strictly speaking, a string is a substring of itself, right? ;)

user2058724 Over a year ago

Yes @thefourtheye.. your solution works, but can you point out why mine does not work?

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