import re

s = input('Email address: ')

# match looks from start string, doesn't require consuming all
# search looks in the middle
match = re.match('([a-zA-Z][a-zA-Z0-9_.]*)@([a-zA-Z0-9][a-zA-Z0-9._]*[a-zA-Z0-9])', s)

if match:
    print('Match!')
    print(match.groups())
else:
    print('Not valid')