Hackerrank - Validating and Parsing Email Addresses Solution

A valid email address meets the following criteria:

• It's composed of a username, domain name, and extension assembled in this format: [email protected]
• The username starts with an English alphabetical character, and any subsequent characters consist of one or more of the following: alphanumeric characters, -,., and _.
• The domain and extension contain only English alphabetical characters.
• The extension is , , or  characters in length.

Given  pairs of names and email addresses as input, print each name and email address pair having a valid email address on a new line.

Hint: Try using Email.utils() to complete this challenge. For example, this code:import email.utilsprint email.utils.parseaddr('DOSHI <[email protected]>')print email.utils.formataddr(('DOSHI', '[email protected]'))

produces this output:

('DOSHI', '[email protected]')
DOSHI <[email protected]>

Input Format

The first line contains a single integer, , denoting the number of email address.
Each line  of the  subsequent lines contains a name and an email address as two space-separated values following this format:

name <[email protected]>

Constraints

Output Format

Print the space-separated name and email address pairs containing valid email addresses only. Each pair must be printed on a new line in the following format:

name <[email protected]>

You must print each valid email address in the same order as it was received as input.

Sample Input

2  
DEXTER <[email protected]>
VIRUS <virus!@variable.:p>

Sample Output

DEXTER <[email protected]>

Explanation

[email protected] is a valid email address, so we print the name and email address pair received as input on a new line.
virus!@variable.:p is not a valid email address because the username contains an exclamation point (!) and the extension contains a colon (:). As this email is not valid, we print nothing.

Solution in Python

import re
import email.utils
for _ in range(int(input())):
    s = input()
    u = email.utils.parseaddr(s)
    if re.search("^[a-z][\w.-]+@[a-z]+\.[a-z]{1,3}$",u[-1],re.I):
        print(s)

Start of line
^

Small letters
[a-z] 

Alphanumeric and _
\w 

Alphanumeric . - and _
[\w.-] 

One or more than one occurrence
+ 

Means .
\. 

Between 1 to 3 occurrence
{1,3} 

End of line
$ 

re.I is used to ignore case so that [a-z] matches both upper and lower case since [a-z] matches lowercase only.