Hcfyk

Given a string taken from the following set:

strings = [
 "The sky is blue and I like it",
 "The tree is green and I love it",
 "A lemon is yellow"
]

I would like to constuct a function which replaces subject, color and optional verb from this string with others values.

All strings match a certain regex pattern as follow:

regex = r"(?:The|A) (?P<subject>w+) is (?P<color>w+)(?: and I (?P<verb>w+) it)?"

The expected output of such function would look like this:

repl("The sea is blue", "moon", "white", "hate")
# => "The moon is white"

Here is the solution I come with (I can't use .replace() because there is edge cases if the string contains the subject twice for example):

def repl(sentence, subject, color, verb):
 m = re.match(regex, sentence)
 s = sentence
 new_string = s[:m.start("subject")] + subject + s[m.end("subject"):m.start("color")] + color
 if m.group("verb") is None:
 new_string += s[m.end("color"):]
 else:
 new_string += s[m.end("color"):m.start("verb")] + verb + s[m.end("verb"):]
 return new_string

Do you think there is a more straightforward way to implement this?

import re

regex = re.compile(
 r'(The|A) '
 r'w+'
 r'( is )'
 r'w+'
 r'(?:'
 r'( and I )'
 r'w+'
 r'( it)'
 r')?'
)


def repl(sentence, subject, colour, verb=None):
 m = regex.match(sentence)
 new = m.expand(rf'1 subject2colour')
 if m[3]:
 new += m.expand(rf'3verb4')
 return new


def test():
 assert repl('The sky is blue and I like it', 'bathroom', 'smelly', 'distrust') == 
 'The bathroom is smelly and I distrust it'
 assert repl('The tree is green and I love it', 'pinata', 'angry', 'fear') == 
 'The pinata is angry and I fear it'
 assert repl('A lemon is yellow', 'population', 'dumbfounded') == 
 'A population is dumbfounded'

Essentially, invert the sections of the regex around which you put groups; they're the things you want to save.