CODEWITHSUNDEEP
pythonregex
DJM
DJM

Reputation: 81

Grab words before and after a matched term

I'm taking my first steps with Python and I have a problem to solve in which I need regex.

I'm parsing several lines of text and I need to grab 5 words before and after a certain match. The term to match is always the same, and lines can have more than one occurrence of that term.

r"(?i)((?:\S+\s+){0,5})<tag>(\w*)</tag>\s*((?:\S+\s+){0,5})"

This works in very specific situations: if there's only one occurence of the term between tags (or if they are well-spaced between them), and if there are enough words before the first occurrence.

The problem is:

1 - if a second occurrence is within the +5 range of the first occurrence, there are no -5 for the second, or the second just becomes engulfed by the first. Overlapping problem?

2 - if there are less than 5 words, or if you up the range to 7 or 8, it just skips the first occurrence to the second or third.

So a line that's something like:

word word word match word word match word word word

Would not be parsed well.

Is there a way to take into account these issues and make it work?

Thank you all in advance!

Upvotes: 2

Views: 353

Answers (1)

Mr Mystery Guest
Mr Mystery Guest

Reputation: 1474

This might be what your after - without using regex

#!/usr/bin/env python



def find_words(s, count, needle):

  # split the string into a list
  lst = s.split()

  # get the index of the where the needle is
  idx = lst.index(needle)

  # s is the start and end of the list you need
  s = idx -count
  e = idx +count

  # print the list as slice notation
  print lst[s:e+1]


def find_occurrences_in_list(s, count, needle):
  # split the string into a list
  lst = s.split()

  idxList = [i for i, x in enumerate(lst) if x == needle]

  # print idxList

  r = []
  for n in idxList:
    s = n-count
    e = n+count
    # append the list as slice notation
    r.append(" ".join(lst[s:e+1]))

  print r

# the string of words
mystring1 = "zero one two three four five match six seven eight nine ten eleven"
# call function to find string, 5 words head & behind, looking for the word "match"
find_occurrences_in_list(mystring1, 5, "match")

# call function to find string, 3 words head & behind, looking for the word "nation"
mystring2 = "Four score and seven years ago our fathers brought forth on this continent a new nation conceived in Liberty and dedicated to the proposition"
find_occurrences_in_list(mystring2, 3, "nation")

mystring3 = "zero one two three four five match six seven match eight nine ten eleven"
find_occurrences_in_list(mystring3, 2, "match")


['one two three four five match six seven eight nine ten']
['continent a new nation conceived in Liberty']
['four five match six seven', 'six seven match eight nine']

Upvotes: 1

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