tweet = input('Enter abbreviation from tweet:\n')

tweet_dict = {
    'LOL': 'LOL = laughing out loud',
    'BFN': 'BFN = bye for now',
    'FTW': 'FTW = for the win',
    'IRL': 'IRL = in real life'
}

try:
    print(tweet_dict[tweet.upper()])
except KeyError:
    print("Sorry, don't know that one")