Regular Expressions

Regular expressions (regex or regexp for short) are special strings that are used to match patterns in text. They are widely used in many programming languages for a variety of purposes, such as validating input, extracting information from text, and finding and replacing text.

A regular expression is typically defined using a syntax that is similar across programming languages, although there may be some differences in the details. The syntax consists of a combination of characters and special characters (also called metacharacters) that have a specific meaning.

Here are a few examples of regular expressions and what they match:

• a: matches the character "a"

• .*: matches any character (except a newline) 0 or more times

• a.*b: matches a string that starts with "a", followed by any character (except a newline) 0 or more times, and ends with "b"

• [a-z]: matches any lowercase letter

• [0-9]: matches any digit

• \d: matches any digit (same as above)

You can use regular expressions with the re module in Python, or with functions or methods provided by other programming languages or libraries. Here is an example of how to use regular expressions in Python:

import re

# Check if a string contains a specific pattern

string = "The quick brown fox"