Python re.findall Function

The re.findall function in Python's re module finds all occurrences of a pattern in a string and returns them as a list. This function is useful for extracting all matches of a pattern from a string.

Table of Contents

1. Introduction
2. re.findall Function Syntax
3. Examples
   • Basic Usage
   • Using Groups in Patterns
   • Finding All Words in a String
   • Using Flags with re.findall
4. Real-World Use Case
5. Conclusion

Introduction

The re.findall function in Python's re module scans a string for all occurrences of a regular expression pattern and returns them as a list. This function is particularly useful when you need to find and extract multiple matches from a string.

re.findall Function Syntax

Here is how you use the re.findall function:

import re

matches = re.findall(pattern, string, flags=0)

Parameters:

• pattern: The regular expression pattern to search for.
• string: The string to search within.
• flags: Optional. Flags that modify the behavior of the pattern, such as re.IGNORECASE, re.MULTILINE, etc.

Returns:

• A list of all non-overlapping matches in the string.

Examples

Basic Usage

Here is an example of how to use the re.findall function to find all digit sequences in a string.

Example

import re

# Finding all digit sequences in a string
matches = re.findall(r'\d+', 'There are 123 apples and 45 bananas.')
print(matches)

Output:

['123', '45']

Using Groups in Patterns

This example demonstrates how to use groups in a regular expression pattern and access the matches.

Example

import re

# Finding all occurrences of a pattern with groups
matches = re.findall(r'(\d+)\s+apples', 'There are 123 apples and 45 bananas. And 678 apples.')
print(matches)

Output:

['123', '678']

Finding All Words in a String

This example demonstrates how to find all words in a string using re.findall.

Example

import re

# Finding all words in a string
matches = re.findall(r'\b\w+\b', 'This is a test string.')
print(matches)

Output:

['This', 'is', 'a', 'test', 'string']

Using Flags with re.findall

This example demonstrates how to use flags with the re.findall function to modify the behavior of the pattern.

Example

import re

# Finding all case-insensitive occurrences of a pattern
matches = re.findall(r'hello', 'Hello world! hello everyone.', re.IGNORECASE)
print(matches)

Output:

['Hello', 'hello']

Real-World Use Case

Extracting Email Addresses

In real-world applications, the re.findall function can be used to extract all email addresses from a text.

Example

import re

def extract_emails(text):
    pattern = r'[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}'
    return re.findall(pattern, text)

# Example usage
text = 'Contact us at support@example.com or sales@example.com. You can also reach out to admin@domain.org.'
emails = extract_emails(text)
print(emails)

Output:

['support@example.com', 'sales@example.com', 'admin@domain.org']

Conclusion

The re.findall function in Python's re module finds all occurrences of a pattern in a string and returns them as a list. This function is useful for extracting all matches of a pattern from a string. Proper usage of this function can enhance the flexibility and power of your string processing tasks in Python.