Master Python Regex: How "+" and "*" Change Your Pattern Matching

In this article we explore the difference between the regex quantifiers “+” and “*” in Python, illustrating how they affect pattern matching.

1. The “+” quantifier requires the preceding character to appear at least once; without it, a greedy pattern matches the shortest possible substring, resulting in “pp”.

2. Changing the pattern from ".*(p.*p).*" to ".*(p.+p).*" replaces “*” with “+”, forcing the characters between the two p’s to appear at least once. Running the program now yields “ppp”.

3. Replacing the three p’s with “php” and executing the same pattern produces the result “php”.

4. If the string is changed to “phhp”, the pattern still matches and returns “phhp”, because the “+” quantifier only requires at least one occurrence of the intermediate characters.

5. In summary, both “*” and “+” are quantifiers that limit how many times the preceding token may appear. “*” allows zero or more occurrences, while “+” requires at least one occurrence.