HackerRank Python Solution - Functionals - Validating Email Addresses with a Filter

• You are given an integer N followed by N 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 [a-z],[A-Z],[0-9],[_-].
• The website name can only have letters and digits [a-z],[A-Z],[0-9].
• The extension can only contain letters [a-z],[A-Z].
• The maximum length of the extension is 3.

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 0 to 9 (both included).

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

Now, you only require those elements that are greater than 10 but less than 80.

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

Example:

• Complete the function fun in the editor below.
• fun has the following parameters:
• 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 N, the number of email addresses.
• N 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
    email_regex = re.compile(r"^[a-zA-Z0-9_-]+@[A-Za-z0-9]+\.[a-zA-Z]{1,3}$")
    if email_regex.match(s):
        return True
    else:
        return False

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)

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