Extract words preceding and following search terms - regex

Question

Suppose I have a text like the following.
The City of New York often called New York City or simply New York is
the most populous city in the United States. With an estimated
population of 8537673 distributed over a land area of about 3026
square miles (784 km2) New York City is also the most densely
populated major city in the United States.
I want to locate the n words preceding and following occurrences of the a search term. For example, n=3 and search term="New York", then
1st occurrence:
words preceding = {The, city, of}
words following = {often, called, New}
2nd occurrence:
words preceding = {York, often, called}
words following = {City, or, simply}
3rd occurence:
words preceding = {City, or, simply}
words following = {is, the, most}
4th occurrence:
words preceding = {miles, 784, km2}
words following = {City, is, also}
How can I do this using regex? I found a similar question here Extract words surrounding a search word but it does not consider multiple occurrences of the search term.
Attempts:
def search(text,n):
word = r"\W*([\w]+)"
groups = re.search(r'{}\W*{}{}'.format(wordn,'place',wordn), text).groups() return groups[:n],groups[n:]

Answer 1

You need to use a positive lookahead assertion in order to handle overlapping matches:
re.findall(r"((?:\w+\W+){3})(?=New York((?:\W+\w+){3}))", t)
Result:
[('The City of ', ' often called New'),
('York often called ', ' City or simply'),
('City or simply ', ' is the most'),
('miles (784 km2) ', ' City is also')]

Answer 2

You may try the following:
((?:\w+\W+){3})(?=New York((?:\W+\w+){3}))
and get your values in group 1 and 2
Sample Source ( run here )
import re
regex = r"((?:\w+\W+){3})(?=New York((?:\W+\w+){3}))"
test_str = "The City of New York often called New York City or simply New York is the most populous city in the United States. With an estimated 2016 population of 8537673 distributed over a land area of about 3026 square miles (784 km2) New York City is also the most densely populated major city in the United States."
matches = re.finditer(regex, test_str)
for match in matches:
print(re.sub(r'\W+', ' ', match.group(1))+" <------>" +re.sub(r'\W+', ' ', match.group(2)))
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