More about regular expressions

You were previously introduced to regular expressions and a couple of symbols that you can use to construct regular expression patterns. In this reading, you'll explore additional regular expression symbols that can be used in a cybersecurity context. You'll also learn more about the re module and its re.findall() function.

Basics of regular expressions

A regular expression (regex) is a sequence of characters that forms a pattern. You can use these in Python to search for a variety of patterns. This could include IP addresses, emails, or device IDs.

To access regular expressions and related functions in Python, you need to import the re module first. You should use the following line of code to import the re module:

import re

Regular expressions are stored in Python as strings. Then, these strings are used in re module functions to search through other strings. There are many functions in the re module, but you will explore how regular expressions work through re.findall(). The re.findall() function returns a list of matches to a regular expression. It requires two parameters. The first is the string containing the regular expression pattern, and the second is the string you want to search through.

The patterns that comprise a regular expression consist of alphanumeric characters and special symbols. If a regular expression pattern consists only of alphanumeric characters, Python will review the specified string for matches to this pattern and return them. In the following example, the first parameter is a regular expression pattern consisting only of the alphanumeric characters "ts". The second parameter, "tsnow, tshah, bmoreno",  is the string it will search through. You can run the following code to explore what it returns: