Examples of Regular Expressions

Regular expressions are widely supported in programming languages such as Python, JavaScript, Java, and many others, making them a versatile tool for string manipulation tasks. At its core, a regular expression is a sequence of characters that define a search pattern. These patterns can include literal characters, metacharacters, and quantifiers, allowing you to match specific sequences of characters within a string.

1) Regular Expressions in Python

Let’s start with a simple example of using regular expressions in Python to match a specific pattern within a string:-

#Example 1: Matching a Pattern in a String

text = "The quick brown fox jumps over the lazy dog."
pattern = r'fox'
if re.search(pattern, text):
    print("Pattern found!")
else:
    print("Pattern not found.")

#Example 2: Extracting Email Addresses from a String

text = "Contact us at [email protected] or [email protected]"
pattern = r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'
email_addresses = re.findall(pattern, text)
print("Email addresses found:", email_addresses)

2) Regular Expressions in JavaScript

With the help of 02 quick examples we can understand the regular expressions in JavaScript.

#Example 1: Matching a Pattern in a String

let text = "The quick brown fox jumps over the lazy dog.";
let pattern = /fox/;
if (pattern.test(text)) {
 console.log("Pattern found!");
} else {
console.log("Pattern not found.");
}

#Example 2: Extracting Email Addresses from a String

let text = "Contact us at [email protected] or [email protected]";
let pattern = /\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b/g;
let emailAddresses = text.match(pattern);
console.log("Email addresses found:", emailAddresses);

3) Regular Expressions in Java

import java.util.regex.*;

public class Main {
public static void main(String[] args) {

#Example 1: Matching a Pattern in a String

String text = "The quick brown fox jumps over the lazy dog.";
       String pattern = "fox";
        if (text.matches("." + pattern + ".")) {
            System.out.println("Pattern found!");
        } else {
            System.out.println("Pattern not found.");
        }

#Example 2: Extracting Email Addresses from a String

String text = "Contact us at [email protected] or [email protected]";
String pattern = "\\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\\.[A-Z|a-z]{2,}\\b";
Pattern emailPattern = Pattern.compile(pattern);
Matcher matcher = emailPattern.matcher(text);
while (matcher.find()) {
    System.out.println("Email address found: " + matcher.group())
}
}
}

Conclusion

Experiment with different patterns and explore the vast capabilities of regular expressions to become a more proficient coder.

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