Regular Expressions (re)

A Regular Expression (RegEx) is a sequence of characters that forms a search pattern. Python has a built-in package called re to work with RegEx.

1. Basic Search

import re

txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)

if x:
  print("YES! We have a match!")

2. Core Functions

• findall(): Returns a list containing all matches.
• search(): Returns a Match object if there is a match anywhere in the string.
• split(): Returns a list where the string has been split at each match.
• sub(): Replaces one or many matches with a string.

3. Practical Validation

Commonly used for validating email addresses or identifying patterns in large text files.

emails = "Contact me at info@example.com or support@site.org"
matches = re.findall(r'[\w\.-]+@[\w\.-]+', emails)
print(matches) # ['info@example.com', 'support@site.org']