Tweepy auth saving tokens

OAuth.py

import tweepy, os

def login():
    #Tokens
    CONSUMER_TOKEN =  ''
    CONSUMER_SECRET =   ''

    auth = tweepy.OAuthHandler(CONSUMER_TOKEN, CONSUMER_SECRET)

    ACC_TOKEN_SV = os.path.expanduser('./._twitter_keys')

    if not os.path.exists(ACC_TOKEN_SV):
        try:
            print("Auth. URL - Write here your PIN after login\n")

            redirect_url = auth.get_authorization_url()
        except tweepy.TweepError:
            print("Error! Token ")

        print(redirect_url)

        p = input('Write your PIN:')

        try:
            auth.get_access_token(p)
        except tweepy.TweepError:
            print("Error! PIN not valid")


        f = open(ACC_TOKEN_SV, 'w')
        f.write(auth.access_token+"\n")
        f.write(auth.access_token_secret)
        f.close()

    f = open(ACC_TOKEN_SV, 'r')
    key = f.readline().strip()

    secret = f.readline().strip()
    f.close()

    auth.set_access_token(key, secret)

    return auth