Task and Solution - Validating Email Addresses With a Filter (HackerRank)

 

You are given an integer  followed by  email addresses. Your task is to print a list containing only valid email addresses in lexicographical order.

Valid email addresses must follow these rules:

• It must have the username@websitename.extension format type.
• The username can only contain letters, digits, dashes and underscores .
• The website name can only have letters and digits .
• The extension can only contain letters .
• The maximum length of the extension is .
  
  

Concept

A filter takes a function returning True or False and applies it to a sequence, returning a list of only those members of the sequence where the function returned True. A Lambda function can be used with filters.

Let's say you have to make a list of the squares of integers from  to  (both included).

>> l = list(range(10))
>> l = list(map(lambda x:x*x, l))

Now, you only require those elements that are greater than  but less than .

>> l = list(filter(lambda x: x > 10 and x < 80, l))

Easy, isn't it?

Example

Complete the function fun in the editor below.

fun has the following paramters:

• string s: the string to test

Returns

• boolean: whether the string is a valid email or not

Input Format

The first line of input is the integer , the number of email addresses.
 lines follow, each containing a string.

Constraints

Each line is a non-empty string.

Sample Input

3
lara@hackerrank.com
brian-23@hackerrank.com
britts_54@hackerrank.com

Sample Output

['brian-23@hackerrank.com', 'britts_54@hackerrank.com', 'lara@hackerrank.com']

Solution 

import re

def fun(s):

    # return True if s is a valid email, else return False

    return bool(re.search(r"^[A-Z0-9a-z-_]+@[A-Z0-9a-z]+\.[A-Za-z]{1,3}$", s))

def filter_mail(emails):

    return list(filter(fun, emails))

if __name__ == '__main__':

    n = int(input())

    emails = []

    for _ in range(n):

        emails.append(input())

filtered_emails = filter_mail(emails)

filtered_emails.sort()

print(filtered_emails)

Source : HackerRank