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Day 10: Regular Expressions

Learn the fundamentals of Regular Expressions in Python and master pattern matching!

Topics:

Introduction to `re` module
Pattern Matching
Common Regex Methods
Special Characters in Regex

1. Introduction to `re` module

The re module in Python provides support for regular expressions, enabling you to perform pattern matching and string manipulation.

To use it, import the module like this:

import re

2. Pattern Matching

Regular expressions allow you to define patterns for matching specific sequences in text. Here are some common patterns:

\\d - Matches any digit (0-9)
\\w - Matches any alphanumeric character (letters and digits)
\\s - Matches any whitespace character (spaces, tabs, line breaks)

3. Common Regex Methods

The re module includes several methods for pattern matching:

# Using re.match() to match a pattern at the beginning of the string
result = re.match(r'\d+', '123abc')
print(result.group())  # Output: 123

# Using re.search() to find the first match
result = re.search(r'\d+', 'abc123xyz')
print(result.group())  # Output: 123

4. Special Characters

Special characters in regular expressions have unique meanings:

. - Matches any character except newline
^ - Matches the beginning of the string
$ - Matches the end of the string
* - Matches 0 or more repetitions of the preceding character or group

Exercises:

Validate an email address using regex: Create a function to validate if an email follows the basic structure username@domain.com
Extract phone numbers: Use regex to extract phone numbers from a text file or string (example format: (123) 456-7890)

Summary

On Day 10, we explored the power of **Regular Expressions** in Python. We learned how to use the re module for pattern matching, and we covered the common methods for searching, matching, and replacing text. You also learned some key special characters in regex and applied this knowledge in exercises.

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