CODEWITHSUNDEEP
pythonstringreplace
Cryssie
Cryssie

Reputation: 3185

Python find all matching substring patterns and replace substring

I want to search if a sentence has particular pattern or not. Do nothing if not found. If pattern found, substitute pattern with another substring in the string. 

line1 = "Who acted as `` Bruce Wayne '' in the movie `` Batman Forever '' ?" 
#Desired Result: Who acted as ``Bruce_Wayne'' in the movie ``Batman_Forever'' ? 

#This is what I have tried..    
def findSubString(raw_string, start_marker, end_marker): 

    start = raw_string.index(start_marker) + len(start_marker)
    end = raw_string.index(end_marker, start)
    return raw_string[start:end]

phrase = findSubString(line1, "``", "''")
newPhrase = phrase.strip(' ').replace(' ', '_')
line1 = line1.replace(phrase, newPhrase)

Current Result: Who acted as ``Bruce_Wayne'' in the movie `` Batman Forever '' ?

So far, I managed to find the first occurrence in the sentence but not the next. How to search for all occurrences with matching pattern?

Upvotes: 2

Views: 3790

Answers (1)

falsetru
falsetru

Reputation: 369454

Using regular expression:

import re

def findSubString(raw_string, start_marker, end_marker):
    return re.sub(
        r'(?<={}).*?(?={})'.format(re.escape(start_marker), re.escape(end_marker)),
        lambda m: m.group().strip().replace(' ', '_'),
        raw_string)

line1 = "Who acted as `` Bruce Wayne '' in the movie `` Batman Forever '' ?"
line1 = findSubString(line1, "``", "''")
assert line1 == "Who acted as ``Bruce_Wayne'' in the movie ``Batman_Forever'' ?"

Without regular expression:

def findSubString(raw_string, start_marker, end_marker): 
    result = []
    rest = raw_string
    while True:
        head, sep, tail = rest.partition(start_marker)
        if not sep:
            break
        body, sep, tail = tail.partition(end_marker)
        if not sep:
            break
        result.append(head + start_marker + body.strip().replace(' ', '_') + end_marker)
        rest = tail
    result.append(rest)
    return ''.join(result)

Upvotes: 4

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