Text search using python

Question

I am working on a text search project, and using text blob to search for sentences from text. TextBlob pulls all the sentences with the keywords efficiently. However for effective research i also want to pull out one sentence before and one after which I am unable to figure.

Below is the code I am using:

def extraxt_sents(Text,word):
    search_words = set(word.split(','))
        sents = ''.join([s.lower() for s in Text])
        blob = TextBlob(sents)
    matches = [str(s) for s in blob.sentences if search_words & set(s.words)]
    print search_words
    print(matches)

@cengizkrbck TextBlob seems to work better than nltk. I a,a not able to figure the one sentence before and one after. — Raghav Shaligram, Jul 21 '14 at 13:14
Try using indices: `[map(str, blob.sentences[i-1:i+2]) for i, s in enumerate(blob.sentences) if search_words & set(s.words)]` — tobias_k, Jul 21 '14 at 13:15
@tobias_k I am getting a list of list and i need to write an excel files with the output. Can you amend the code to get a list?? — Raghav Shaligram, Jul 21 '14 at 17:04
@RaghavShaligram What exactly do you mean? Do you want to flatten the list, i.e. instead of `[(prev1, match1, next1), (prev2, match2, next2), ...]` get `[prev1, match1, next1, prev2, match2, next2, ...]`? — tobias_k, Jul 21 '14 at 17:48
@tobias_k yes..since i have to iterate over the list and write it to an excel file — Raghav Shaligram, Jul 21 '14 at 18:09
I wrote a .join and iterated over the list and joined the sentences to be written to an excel file :) — Raghav Shaligram, Jul 21 '14 at 18:27

score 1 · Accepted Answer · edited May 23 '17 at 10:28

If you want to get the lines before and after the match, you can either create a loop and memorize the previous line, or use slices, like [from:to] on the blob.sentences list.

The best way might be to use the enumerate bultin function.

match_region = [map(str, blob.sentences[i-1:i+2])     # from prev to after next
                for i, s in enumerate(blob.sentences) # i is index, e is element
                if search_words & set(s.words)]       # same as your condition

Here, blob.sentences[i-1:i+2] will extract the sublist spanning from index i-1 (inclusive) to index i+2 (exclusive), and map turns the elements in this list into strings.

Note: Actually, you might want to replace i-1 with max(0, i-1); otherwise i-1 could be -1 and Python would interpret this as the last element, yielding an empty slice. If i+2 is higher than the list's length, on the other hand, this will not be a problem.

Text search using python

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