Python - re.compile()

In Python, re.compile() from the re module creates a regex object from a regular expression pattern. This object lets you perform operations like search(), match(), and findall(). In this article, we will understand about re.compile() method.

import re

# Compile the pattern
pattern = re.compile(r'\d+')

# Search for digits in a string
result = pattern.search("I have 3 cats.")

if result:
    print(result.group()) 

3

Syntax of re.compile()

re.compile(pattern, flags=0)

Parameters:

1. pattern (str):
   • The regular expression pattern you want to compile.
   • Example: r'\d+' (matches one or more digits).
2. flags (optional):
   • Modifiers that change the behavior of the regex.
   • Common flags:
     • re.IGNORECASE or re.I: Ignore case sensitivity.
     • re.MULTILINE or re.M: Allow ^ and $ to match start and end of lines.
     • re.DOTALL or re.S: Allow . to match newline characters.
     • re.VERBOSE or re.X: Allow adding comments and whitespace for better readability.

Without using flags

In this code we are not using flags which is an optional parameter:

import re

# Compile a regex pattern
pattern = re.compile(r'\d{3}-\d{2}-\d{4}')

# Use the compiled pattern to match
text = "My SSN is 123-45-6789."

match = pattern.search(text)
if match:
    print(f"Found: {match.group()}") 

Found: 123-45-6789

With Using Flags

In this code we are using flags (Modifiers that change the behavior of the regex.)

import re

# Compile a case-insensitive regex
pattern = re.compile(r'hello', re.IGNORECASE)

# Use the compiled pattern
text = "Hello, GeeksforGeeks!"

match = pattern.search(text)
if match:
    print(f" {match.group()}")