Regular Expressions

Regular Expressions (regex) are a powerful mini-language for describing and matching patterns within text - used constantly in data cleaning to validate, extract, or transform messy, unstructured text data.

Basic Pattern Matching

import re

text = "Contact us at support@uncodemy.com"

match = re.search(r"\w+@\w+\.\w+", text)
if match:
    print(match.group())   # support@uncodemy.com

Common Regex Functions

• re.search() - finds the first match anywhere in the string
• re.match() - checks for a match only at the beginning of the string
• re.findall() - returns a list of all matches found in the string
• re.sub() - replaces matched patterns with a new value

import re

text = "Call 9876543210 or 9123456780 for support"

numbers = re.findall(r"\d{10}", text)
print(numbers)   # ['9876543210', '9123456780']

cleaned = re.sub(r"\d{10}", "[REDACTED]", text)
print(cleaned)   # Call [REDACTED] or [REDACTED] for support

Common Pattern Symbols

• \d - any digit, \w - any word character, \s - any whitespace
• * - zero or more, + - one or more, ? - zero or one
• ^ - start of string, $ - end of string

Coming Up Next

To close out this module, the final topic takes a deeper, more complete look at Exception Handling in Python.