Remove multiple words from string using list of indexes

Question

sentence = 'Two Dogs and Three Cats'

list_of_indices = [[0,3], [13, 18]]

I wish to remove multiple indices from a string based on its index position by referencing a nested list of index values (which may have more than 2 elements).

I am able to remove a single index range from the string (e.g remove the word Two from the sentence using S = sentence[:0] + sentence[3:] but how do I modify this code to remove multiple range of indices by referencing list_of_indices?

I tried one other method:

to_remove = []

for i in list_of_indices:
    word = sentence[i[0]: i[1]]
    to_remove.append(word)

resultwords  = [word for word in sentence.split() if word not in to_remove]
print(resultwords)
result = ' '.join(resultwords)
print(result)

However, it would not work if the word contains other symbols in the sentence e.g. for sentence = ':Two: Dogs and Three Cats', it would not remove Two

You keep using "words" and "letters" interchangeably. Which are you trying to remove? Letters, whole words, or both? — ddejohn
– ddejohn, Commented Aug 25, 2021 at 4:55
@blorgon I am trying to remove based on index position, the values are stored in list_of_indices — abc
– abc, Commented Aug 25, 2021 at 4:56
question: will list_of_indices be a sorted list with no overlapping indices? — theusaf
– theusaf, Commented Aug 25, 2021 at 4:57
@abc that doesn't answer my question. "Remove by index position" implies removing single characters, but your code seems to be trying to remove whole words via slicing. Why are you doing it this way? Where are your lists of slice indices coming from? What does your statement at the end claiming "it would not work" mean? If your slice indices are correct then it would still work. — ddejohn
– ddejohn, Commented Aug 25, 2021 at 5:05

Tim Roberts · Accepted Answer · 2021-08-25 05:03:48Z

2

The key, I think, is not to think about removing, but to think about what you're keeping.

sentence = 'Two Dogs and Three Cats'
list_of_indices = [[0,3], [13, 18]]

keep = []
last = 0
for a,b in list_of_indices:
    keep.append( sentence[last:a] )
    last = b
keep.append(sentence[last:])
print( ''.join(keep) )

Output:

 Dogs and Cats

answered Aug 25, 2021 at 5:03

Tim Roberts

55.3k4 gold badges29 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Y.T. · Accepted Answer · 2021-08-25 05:19:23Z

1

If complexity isn't a concern, here is an O(NM) approach with the method you suggested, where N is the length of sentence, M is the length of list_of_indices. But be aware of the extraneous space introduced between words that you might want to take care of.

sentence = 'Two Dogs and Three Cats'

list_of_indices = [[0,3], [13, 18]]


for indices in reversed(list_of_indices):
    sentence = sentence[:indices[0]] + sentence[indices[1]:]

print(sentence)

output:

Dogs and  Cats

answered Aug 25, 2021 at 5:19

Y.T.

2,8162 gold badges17 silver badges34 bronze badges

Comments

Random_Pythoneer59 · Accepted Answer · 2021-08-25 05:01:37Z

-1

You could convert it to a list then add the letters based on index to a new string:

word = 'Hello'
indices = [0, 4]

word_list = list(word)
new_word = ''
for index, value in enumerate(word_list):
    if not index in indices:
        new_word += value

print(new_word)

Output:

ell

answered Aug 25, 2021 at 5:01

Random_Pythoneer59

7286 silver badges14 bronze badges

Collectives™ on Stack Overflow

Remove multiple words from string using list of indexes

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related