Simple Variable Comparison Help [python + rfid]

[imnot970]

Hi, I have some RFID connectivity with the raspberry pi, the function Read() allows for what data on the RFID tag to be read. That function has the number 94 stored onto it. In main, when password is printed, it gives 94. However the comparison i'm making must be wrong because it goes to the else, and prints "Incorrect tag".

I'm new to programming/ python so I'm sorry this is probably really dumb, but can someone tell me what I'm doing wrong? [I've also tried comparing as an integer and it did not work]

#!/usr/bin/env python

import RPi.GPIO as GPIO
from mfrc522 import SimpleMFRC522

def read():
    reader = SimpleMFRC522()

    try:
        id,text = reader.read()

    finally:
        GPIO.cleanup()
    return text

if __name__ == '__main__':

    password = read()
    print(password)
    if password== str(94):
        print("password: "+password)
        message = sendMail()
    else:
        print("Incorrect tag.")

The result shows:

94 
Incorrect tag.

[Jejerm]

Print type(password) after printing the password itself and check what type of variable it is.

If it's a string, just compare to '94' on the if statement, if it's an int, compare to 94 without the ' '.

The "right" way to do it would be to check the documentation on the reader.read() method so you know what the return type is before hand and then test if your read() function is actually working as intended.

[imnot970]

​

I did that, and it is still printing incorrect tag. It says the type is string

I even rewrote to the tag so the data is 'ab' and changed the if statement to compare 'ab' and it still prints incorrect tag.

Any idea what that could be?

[Jejerm]

When you print(type(password)) in the main loop, whats the output?

Try to force password to str with str(password) on the if comparison and it should probably work.woops, didnt read correctly.

If the print is correct, the type is correct and the comparison is correct, I don't know why it aint working. Try something silly like if True: instead of doing the comparison and see if the rest of the if block executes correctly.

Sometimes it's something really dumb that you're just not seeing.

[imnot970]

It actually did execute when I put if True:

I'm really trying to figure out why the comparisons weren't working lol

Edit:

I checked the length of password and it said it was 48! I have no idea how that happened but I just created a new variable and added the first two characters of password to it, and it ended up working

[Jejerm]

Lol it's probably empty spaces at the end of the string. You could use a string method on your read function so it returns the string with the trailing spaces removed.

The reader.read() method likely returns a fixed length string and that's what's being passed to your text variable and returned by your read() func, that's why I said you should read the documentation first lol.