import logging
logging.basicConfig()

import sys
import time
import errno
import nfc

def connected(tag):
    print(tag)
    return True

def connect_reader(path):
    while True:
        try:
            return nfc.ContactlessFrontend(path)
        except IOError as error:
            time.sleep(0.5)
            continue

if __name__ == '__main__':
    while True:
        try:
            clf = connect_reader("usb")
        except KeyboardInterrupt:
            sys.exit()

        try:
            clf.connect(rdwr={'on-connect': connected})
        finally:
            clf.close()