Master Python Regex: Using Curly Braces {} for Precise Pattern Matching

Today we continue sharing basic knowledge of Python regular expressions, focusing on the special character "{}".

The "{}" character acts as a quantifier that limits the number of occurrences of the preceding element. It has three common forms: "{n}", "{n,}", and "{n,m}". For example, "{1}", "{1,}", and "{1,3}".

Examples:

1. Limiting the preceding character to appear exactly once. Using a greedy match, the pattern "p.{1}p" matches "pap".

2. Changing the pattern to ".*(p.{2}p).*" yields no output because no substring satisfies the condition.

3. Modifying the original string allows the pattern ".*(p.{2}p).*" to produce a match.

4. The quantifier "{1,}" means the preceding character appears at least once; "{2,}" means at least twice; "{3,}" means at least three times, and so on.

5. The quantifier "{1,3}" means the preceding character appears between one and three times inclusive; similarly "{2,5}" means between two and five times.

In greedy mode, the engine scans from right to left; for the pattern with "{1,3}", the substring "phhhhp" (four occurrences) is rejected, and the engine continues to find "paap", which satisfies the condition.

6. Using "{3,5}" yields the match "phhhhp".

Did you get the usage of the special character "{}" in regular expressions?