Regular Expressions (learnpython.org)

Regular expressions, commonly known as regex, are sequences of characters that define a search pattern. They enable us to perform advanced text matching and manipulation by using metacharacters, quantifiers, and character classes. Regular expressions are widely used for tasks like validation, parsing, and data extraction.

#Regular Expressions Example
import re
pattern = re.compile(r"\[(on|off)\]") # Slight optimization
print(re.search(pattern, "Mono: Playback 65 [75%] [-16.50dB] [on]"))
# Returns a Match object!
print(re.search(pattern, "Nada...:-("))
# Doesn't return anything.
# End Example

# Exercise: make a regular expression that will match an email
def test_email(your_pattern):
    pattern = re.compile(your_pattern)
    emails = ["john@example.com", "python-list@python.org", "wha.t.`1an?ug{}ly@email.com"]
    for email in emails:
        if not re.match(pattern, email):
            print("You failed to match %s" % (email))
        elif not your_pattern:
            print("Forgot to enter a pattern!")
        else:
            print("Pass")
pattern = r"" # Your pattern here!
test_email(pattern)

Regular expressions in Python are created using the re module. The syntax allows us to define patterns by combining literal characters, metacharacters, and special sequences. With regular expressions, we can perform operations like searching for specific patterns, replacing text, and extracting information.

Regular expressions offer a range of powerful features for text manipulation. By leveraging capturing groups, quantifiers, and lookahead/lookbehind assertions, we can perform complex operations like matching multiple occurrences, finding boundaries, and even performing conditional matching.

Regular Expressions Exercise Solution

#Code Completed
import re
def test_email(your_pattern):
    pattern = re.compile(your_pattern)
    emails = ["john@example.com", "python-list@python.org", "wha.t.`1an?ug{}ly@email.com"]
    for email in emails:
        if not re.match(pattern, email):
            print("You failed to match %s" % (email))
        elif not your_pattern:
            print("Forgot to enter a pattern!")
        else:
            print("Pass")
# Your pattern here!
pattern = r"\"?([-a-zA-Z0-9.`?{}]+@\w+\.\w+)\"?"
test_email(pattern)

Regular expressions find applications in various domains, such as web scraping, data cleaning, form validation, and text processing. Their flexibility and efficiency make them invaluable in tasks involving complex text manipulation and pattern matching.