functional_email.py

"""

Problem Statement

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


A valid email address is of the format username@websitename.extension
Username can only contain letters, digits, dash and underscore. Website name can have letters and digits. Maximum length of the extension is 3. 


Input Format

An integer N followed by N lines, each containing a string.

Constraints 
Each line is a nonempty string.

Output Format

A list containing valid email addresses in lexicographic order. If the list is empty, just output an empty list, [].

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']
Concept

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

Lets say you have to make a list of 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 which are greater than 10 and less than 80.

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

Easy isn't it!

"""
import re
k = re.compile("^[a-zA-Z][\w-]*@[a-zA-Z0-9]+\.[a-zA-Z]{1,3}$")
lst = [raw_input() for _ in xrange(input())]
lst = filter(k.match, lst)
print sorted(lst)