Regex

Regex is a sequence of characters that defines a search pattern used for matching, searching, and manipulating text. It’s commonly used in data extraction and processing to identify specific patterns in strings, such as validating input, cleaning data, or scraping information from websites.

Also known as: Regular expressions, Pattern matching, RegExp

Comparisons

  • Regex vs. String Matching: While regex is used for complex pattern matching, string matching only searches for exact matches.
  • Regex vs. Wildcards: Wildcards allow basic pattern matching, but regex provides much more flexibility and structure for advanced searches.

Pros

  • Highly flexible for complex text searches and manipulations.
  • Can simplify text processing by eliminating the need for complicated conditional statements.
  • Supported across many programming languages and tools.

Cons

  • Can be hard to read or write, especially with complex patterns.
  • Can impact performance when working with large datasets.
  • Small errors in patterns can lead to inefficient or incorrect results.

Example

A developer uses regex to validate email addresses in a user registration form:

import re
email = "user@example.com"
pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
if re.match(pattern, email):
    print("Valid email!")
else:
    print("Invalid email.")

This pattern ensures the email address follows the correct format by checking the structure before and after the @ symbol.

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