Basic Metacharacters

Lesson 6 of 28 in Coddy's RegEx in Python course.

Metacharacters are special characters in regex that have unique meanings and functions. They help define the patterns for matching text in a powerful and flexible way.

Here are some of the most common metacharacters and their meanings:

. (Dot): Matches any single character except a newline.
^ (Caret): Matches the start of a string.
$lt;/strong> (Dollar Sign): Matches the end of a string.
* (Asterisk): Matches zero or more repetitions of the preceding element.
+ (Plus Sign): Matches one or more repetitions of the preceding element.
? (Question Mark): Matches zero or one repetition of the preceding element.
[] (Square Brackets): Used to define a character class.
| (Pipe): Acts as an OR operator.
() (Parentheses): Groups patterns together.

Here is a simple example using the dot . metacharacter:

import re

text = "cat, cot, cut, c.t"
pattern = "c.t"

matches = re.findall(pattern, text)

print(matches)  # Output: ['cat', 'cot', 'cut', 'c.t']

In the above example, the pattern c.t matches any three-character string that starts with "c" and ends with "t", with any single character in between.

Challenge

Easy

Write a program that uses the . metacharacter to find all three-letter words in the string "bat, bet, bit, but, bot".

Try it yourself

import re

text = "bat, bet, bit, but, bot"
pattern = "???" # Complete here

matches = re.findall(pattern, text)

print(matches)

All lessons in RegEx in Python

1Introduction

Introduction

4Anchors and Quantifiers

Anchors Boundaries Quantifiers Repetitions

7Final Challenges

Extracting Hashtags Finding Email Addresses Valid Phone Numbers Finding Dates Capitalized Words

2re Library

findall search split sub

5Grouping and Advanced Patterns

Grouping Capturing Pipe Operator Alternation Lookaheads Lookbehinds

3Basic Pattern Syntax

Basic MetacharactersLiterals Character Classes Ranges Common Predefined Classes Advanced Predefined Classes

6Advanced Techniques

Escape Metacharacters Escape Sequences