read_uid.py

import time
from smartcard.System import readers
from smartcard.Exceptions import NoCardException, CardConnectionException

# Find PICC reader
reader_list = readers()
print("Readers:", reader_list)

picc_reader = None
for r in reader_list:
    if "PICC" in str(r):
        picc_reader = r
        break

if picc_reader is None:
    print("No PICC reader found!")
    exit()

connection = picc_reader.createConnection()

last_uid = None

print("Waiting for NFC cards... Place a card on the reader.\n")

while True:
    try:
        # Try to connect
        connection.connect()

        GET_UID = [0xFF, 0xCA, 0x00, 0x00, 0x00]
        response, sw1, sw2 = connection.transmit(GET_UID)

        if sw1 == 0x90 and sw2 == 0x00:
            uid = "".join("{:02X}".format(x) for x in response)

            # Only print when UID changes
            if uid != last_uid:
                print("Card detected! UID:", uid)
                last_uid = uid
        else:
            last_uid = None

    except NoCardException:
        # Card removed → reset state
        if last_uid is not None:
            print("Card removed.")
            last_uid = None

    except CardConnectionException:
        last_uid = None

    time.sleep(0.2)  # prevent CPU overload