Python Regular Expressions

Regular expressions, or regex, provide patterns for searching, extracting, validating, and replacing text. Python provides regex support through the built-in re module.

Search for Text

              
            
Python
Find a pattern inside a string.
import re

text = "Python is powerful"
result = re.search("Python", text)

if result:
    print("Found")

Common Regex Patterns

              
            
TEXT
Common regular expression symbols.
^   Start of string
$   End of string
.   Any character
*   Zero or more
+   One or more
?   Zero or one
\d  Digit
\w  Word character
\s  Whitespace

Find All Matches

              
            
Python
Extract all numbers from a string.
import re

text = "Order 123 and order 456"
numbers = re.findall(r"\d+", text)

print(numbers)

Replace Text

              
            
Python
Replace matching text with another value.
import re

text = "Python is fun"
result = re.sub(r"fun", "powerful", text)

print(result)

Validate Input

Regular expressions can be used to check whether text follows a required pattern.

              
            
Python
Validate a simple numeric string.
import re

value = "12345"

if re.fullmatch(r"\d+", value):
    print("Valid number")
else:
    print("Invalid number")

Compile a Pattern

Use re.compile() when the same pattern will be reused multiple times.

              
Python
Create and reuse a compiled regex pattern.
import re

pattern = re.compile(r"\d+")

print(pattern.findall("ID 123, Code 456"))

Summary

Python's re module provides powerful tools for working with text patterns. Use search(), findall(), sub(), fullmatch(), and compile() for common regex tasks.