Python re.Match Tutorial (With Examples)

Regular expressions, often referred to as regex or regexp, provide a powerful and flexible way to search, match, and manipulate text patterns. In Python, the re module is used to work with regular expressions. One of the important concepts within the re module is the re.Match object. The re.Match object represents the result of a successful match between a regular expression pattern and a string. This tutorial will delve into the re.Match object and demonstrate its usage with examples.

Table of Contents

1. Introduction to re.Match Object
2. Accessing Matched Text and Group Information
3. Match Object Methods

• 3.1. .group()
• 3.2. .start()
• 3.3. .end()
• 3.4. .span()
• 3.5. .groups()

1. Example 1: Basic Usage
2. Example 2: Extracting Data from URLs
3. Conclusion

1. Introduction to re.Match Object

When using regular expressions in Python, the re module returns a re.Match object if a pattern is successfully matched within a string. This object contains information about the match, including the matched text, the starting and ending positions of the match, and any captured groups if present in the pattern.

2. Accessing Matched Text and Group Information

The re.Match object provides various methods and attributes to access information about the matched text and any captured groups.

• .group(): Returns the matched text.
• .start(): Returns the starting position of the match.
• .end(): Returns the ending position of the match.
• .span(): Returns a tuple containing the starting and ending positions.
• .groups(): Returns a tuple containing all captured groups.

3. Match Object Methods

3.1. .group()

The .group() method of the re.Match object returns the actual text that was matched by the regular expression pattern. This is particularly useful when the pattern contains capturing groups.

import re

pattern = r'(\d{2})-(\d{2})-(\d{4})'
text = 'Date: 22-08-2023'

match = re.search(pattern, text)
if match:
    print("Matched text:", match.group())  # Output: 22-08-2023

3.2. .start()

The .start() method returns the starting index of the matched text within the original string.

import re

pattern = r'\d+'
text = 'The price is 200 dollars.'

match = re.search(pattern, text)
if match:
    print("Start index:", match.start())  # Output: 12

3.3. .end()

The .end() method returns the ending index of the matched text within the original string.

import re

pattern = r'\d+'
text = 'The price is 200 dollars.'

match = re.search(pattern, text)
if match:
    print("End index:", match.end())  # Output: 15

3.4. .span()

The .span() method combines the .start() and .end() methods, returning a tuple containing both indices.

import re

pattern = r'\d+'
text = 'The price is 200 dollars.'

match = re.search(pattern, text)
if match:
    start, end = match.span()
    print("Start index:", start)  # Output: 12
    print("End index:", end)      # Output: 15

3.5. .groups()

The .groups() method returns a tuple containing all the captured groups from the regular expression pattern.

import re

pattern = r'(\d{2})-(\d{2})-(\d{4})'
text = 'Date: 22-08-2023'

match = re.search(pattern, text)
if match:
    print("Captured groups:", match.groups())  # Output: ('22', '08', '2023')

4. Example 1: Basic Usage

Let’s explore a simple example that demonstrates the usage of the re.Match object.

import re

pattern = r'\b\d+\b'
text = 'The numbers are 42, 1001, and 7.'

matches = re.finditer(pattern, text)
for match in matches:
    print("Matched text:", match.group())
    print("Start index:", match.start())
    print("End index:", match.end())
    print("Indices:", match.span())
    print()

5. Example 2: Extracting Data from URLs

Regular expressions are often used to extract specific information from structured data, such as URLs. In this example, we’ll use the re.Match object to extract domain names from a list of URLs.

import re

pattern = r'https?://(www\.)?(\w+\.\w+)'
urls = [
    'https://www.example.com',
    'http://blog.example.org',
    'https://api.example.net/v1',
]

for url in urls:
    match = re.search(pattern, url)
    if match:
        print("URL:", url)
        print("Domain:", match.group(2))
        print()

6. Conclusion

The re.Match object in Python’s re module is a crucial component when working with regular expressions. It provides a wealth of information about successful pattern matches, such as the matched text, indices, and captured groups. Understanding how to use the methods and attributes of the re.Match object enhances your ability to manipulate and extract data from strings effectively. By practicing with different examples and scenarios, you can become proficient in leveraging the power of regular expressions and the re.Match object to tackle various text manipulation tasks.