10.4 Regular Expressions (RegEx)

Introduction to Regular Expressions with the "re" module for powerful pattern-based string searching, matching, and manipulation.

Regular Expressions (or RegEx) are a specialized mini-language used to describe patterns in text. They allow you to perform complex searches, validation checks, and replacements on strings with incredible flexibility and power. Python's `re` module provides all the necessary functions to work with RegEx.

Main Functions of re:

`re.search(pattern, string)`: Scans the entire string and returns the first match object it finds.
`re.match(pattern, string)`: Attempts to match the pattern only at the beginning of the string.
`re.findall(pattern, string)`: Finds all non-overlapping matches of the pattern and returns them as a list of strings.
`re.sub(pattern, replacement, string)`: Replaces all occurrences of the pattern with the `replacement` value.

import re

text = "My email is test@example.com and my phone number is 210-1234567."
email_pattern = r"[\w\.-]+@[\w\.-]+\.\w+"

match = re.search(email_pattern, text)
if match:
    print(f"Found email: {match.group()}")

# Find all numbers
numbers = re.findall(r"\d+", "Year 2024, Month 07, Day 18")
print(f"Found numbers: {numbers}")

# Hide phone numbers
new_text = re.sub(r"\d{3}-\d{7}", "XXX-XXXXXXX", text)
print(f"Text with hidden number: {new_text}")

Practical Exercises

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10.4 Regular Expressions (RegEx)

Main Functions of re:

Practical Exercises

Exercise 1:Write a generator that produces the first n Fibonacci numbers. The sequence starts with 0, 1, and each subsequent number is the sum of the two preceding ones.

Exercise 2:Create a decorator that measures and prints the execution time of a function. Use time.sleep() for simulation.

Exercise 3:Use RegEx (re.findall) to extract all words that start with a capital letter from a sentence.

Exercise 4:Use RegEx (re.sub) to replace all occurrences of numbers in a sentence with the "#" symbol.

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