如何修复Python中的“列表索引超出范围”错误？

Question

I'm setting up the RFID reader for the attendance system. But when I place my tag to the reader, it was interrupted with the Tag id - which I externally stored to a database.

#//////place your tag//////

print("Now place your tag to write")
rdr.wait_for_tag()

(error, data) = rdr.request()
if not error:
    print("\nDetected: " + format(data, "02x"))

(error, uid) = rdr.anticoll()
if not error:
    print("Card read UID: " +str(uid[0])+str(uid[1])+str(uid[2])+str(uid[3]))

tagid = str(uid[0])+str(uid[1])+str(uid[2])+str(uid[3]) 

print("Written..!")
print(tagid)


cursor.execute("insert into rfid_check (uid,firstname,age,tag_id) values ('%s','%s','%s','%s')" %(user_id,fname, ag_e, tagid))
connection.commit()
print("Data was successfully Added...!")

tagid = str(uid[0])+str(uid[1])+str(uid[2])+str(uid[3]) 
IndexError: list index out of range

Answer 1

Your code structure is not correct. Try to indent rdr.anticoll() with this whenever the tag request is incorrect no process will occur.

Try the line of codes for better visualization:

print("Now place your tag to write")
rdr.wait_for_tag()

(error, data) = rdr.request()
if not error:
    print("\nDetected: " + format(data, "02x"))

    (error, uid) = rdr.anticoll()
    if not error:
        print("Card read UID: " +str(uid[0])+str(uid[1])+str(uid[2])+str(uid[3]))

        tagid = str(uid[0])+str(uid[1])+str(uid[2])+str(uid[3]) 

        print("Written..!")
        print(tagid)
        cursor.execute("insert into rfid_check (uid,firstname,age,tag_id) values ('%s','%s','%s','%s')" %(user_id,fname, ag_e, tagid))
        connection.commit()
        print("Data was successfully Added...!")
else:
    print("Unsuccessful")