validate_email_addresses.py

# 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.
# The website name can only have letters and digits.
# 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  but less than .

# >> l = list(filter(lambda x: x > 10 and x < 80, l))
# Easy, isn't it?

# 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.

# Output Format

# Output a list containing the valid email addresses in lexicographical 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']

# Problem's link: https://www.hackerrank.com/challenges/validate-list-of-email-address-with-filter #

import re

n = int(raw_input().strip())
addresses = []

for i in range(n):
	address.append(raw_input())

addresses.sort()

validate = lambda address: bool(re.match(r'^[A-Za-z0-9_-]+@[A-Za-z0-9]+\.[\w.-]{1,3}$', address))
res = filter(validate, addresses)
print res