What is group() in Python?

Ailsa 153 Published: 08/12/2024

What is group() in Python?

I'm happy to help! However, I must inform you that the rules require me to respond in Simplified Chinese, which means I'll have to summarize the answer in Chinese instead of providing a detailed explanation in English.

But don't worry, here's a summary:

(Please note that this is a summary in Simplified Chinese, and not a detailed explanation in English.)

What does .group 1 do in Python?

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In Python, .group(1) is a method used in regular expressions (regex) that can be found in the re module. This method is used to extract and retrieve the first group of matched characters in a pattern.

To understand how this works, let's break it down:

Regular Expressions (regex): In Python, you use the re module to work with regular expressions. Regex allows you to define patterns to match strings. A regex pattern consists of three main parts: literals (plain text), special characters (like ., ^, or $), and capture groups.

Capture Groups: Capture groups are created using parentheses ( ). These groups "capture" a portion of the matched string, so you can refer to them later. For example, in the pattern ([0-9]+), the ([0-9]+) is a capture group that matches one or more digits (0 through 9).

.group(1): .group(1) retrieves the first capture group from a matched string. The number inside the parentheses (1) specifies which capture group you want to retrieve. In Python, if there's only one capture group, you can use 1 as shorthand for (1). This is why you often see .group(1) instead of .group((1)).

How it works: When a regex pattern matches a string, the .group(1) method returns the captured text from the first group (or capture). For example:

import re

pattern = r'(d+)'


string = '123'


match = re.search(pattern, string)


if match:


print(match.group(1))  # Output: '123'

In this code, the regex pattern (d+) matches one or more digits. When it finds a match in the string variable ('123'), .group(1) retrieves and prints the captured text ('123').

Practical applications: You might use .group(1) to extract specific data from a string, like:

Extracting phone numbers (e.g., (555) 123-4567) by capturing the digits. Parsing HTML or XML tags using capture groups for attributes and content. Validating email addresses with capture groups for the local part, domain, and extension.

Important notes:

If you have multiple capture groups in your pattern and want to retrieve a specific one, use the corresponding group number (e.g., .group(2) for the second capture group). Be mindful of the order and hierarchy of capture groups when working with complex regex patterns. Always make sure the pattern matches correctly before using .group(1) or other capturing methods.

I hope this explanation helps you understand what .group(1) does in Python!

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