Day 18/90: Regex Challenge with re.sub() in Python

Day 18 in the books 🔥 Regex keeps getting more interesting! Here’s your LinkedIn-style post for Day 18, matching the tone and structure of your earlier posts: Day 18/90 of #90DaysOfCode Today’s HackerRank challenge was about transforming strings using re.sub() in Python. The task focused on replacing logical operators in a string: Replace && with and Replace || with or But only when they appear between spaces (not inside other words or symbols). At first, I thought of using simple string replace methods. But then I realized this problem needed pattern-based replacement, not blind substitution. That’s where re.sub() came in. By using regex with lookahead and lookbehind, I was able to: Match only valid && and || operators Avoid replacing characters in the wrong places Cleanly transform the string in one pass Instead of manually scanning character by character, regex allowed me to describe what to replace using a pattern — and Python handled the rest. Key takeaway: re.sub() is powerful because it lets you modify strings based on patterns, not just exact matches. Understanding lookarounds ((?<= ) and (?= )) makes regex much more precise and safer for real-world text processing.

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