Master Greedy vs. Non-Greedy Matching in Python’s Regular Expressions

Improve Your RegEx Skills by Learning How to Control Pattern Consumption

Max N
3 min readApr 6, 2024

Have you ever encountered unexpected results when applying regular expressions in your Python scripts? Understanding greedy and non-greedy matching behavior could be the missing piece to crafting efficient and accurate patterns tailored to your needs.

Python’s built-in re library provides extensive capabilities for text manipulation through regular expressions (regex). Two critical aspects govern the consumption of regex patterns: greediness and laziness. Familiarizing yourself with these concepts helps avoid ambiguous situations and improves overall performance.

In this article, we dive deep into the mechanics behind greedy and non-greedy matching, exploring practical examples to solidify your comprehension.

What Is Greedy Matching?

Greedy matching refers to a regex engine consuming as much input as possible while still producing valid matches. When encountering quantifiers (such as *, +, or {m,n}), greedy engines attempt to find the longest possible matches first, potentially leading to undesirable outcomes.

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Max N

A writer that writes about JavaScript and Python to beginners. If you find my articles helpful, feel free to follow.