08-2 Python Tutorial - Getting Started with Regular Expressions

What is a Regular Expression?

A regular expression is a powerful tool for matching strings to specific patterns. It is mainly used for data validation, searching, and text processing tasks. Utilizing regular expressions in programming languages, especially in Python, allows you to easily handle complex pattern matching.

Using Regular Expressions in Python

The Python re module offers various functions related to regular expressions. Commonly used functions include match, search, findall, and finditer.


# Import the re module
import re

# Pattern matching example
pattern = re.compile(r'\d+')

# Search for numbers in a string
match = pattern.search("The cost is 1200 won.")
if match:
    print("Number found:", match.group())

Basic Patterns in Regular Expressions

You can perform more complex pattern matching through commonly used metacharacters in regular expressions. For example:

. : Any single character
^ : Start of the string
$ : End of the string
* : Zero or more repetitions
+ : One or more repetitions
? : Zero or one repetition

Advanced Pattern Matching

To use regular expressions more deeply, you need to understand advanced features such as grouping and capturing, lookaheads, and lookbehinds.


# Grouping example
pattern = re.compile(r'(\d{3})-(\d{3,4})-(\d{4})')
match = pattern.search("The phone number is 010-1234-5678.")
if match:
    print("Area code:", match.group(1))
    print("Middle number:", match.group(2))
    print("Last number:", match.group(3))

Useful Examples of Regular Expressions

Regular expressions can be used to identify and process various string patterns. For example, you can check the validity of an email address or extract URLs from text.

Practical Examples

We will explore applications of regular expressions through various real-world cases. This section will demonstrate how regular expressions can contribute to problem-solving with specific code examples.

Cautions When Using Regular Expressions

While regular expressions are a powerful tool, performance issues may arise at times. You should be cautious when applying them to very complex patterns or large datasets. Additionally, you should consider readability and maintainability when using them.

Conclusion

Regular expressions are a very useful feature in programming languages like Python. With sufficient practice and understanding, you can write code more efficiently and concisely.

08-2 Python Tutorial – Getting Started with Regular Expressions