Python2 code runs correctly in terminal, but not when executed as Python3

Question

Below code waits for commands from Android Bluetooth Terminal (ie Blue Term): 0 (dim LED) or 1 (light LED).

1. When this program is ran in RPI Putty terminal as python 5EE-Bluetooth-LED.py it performs as designed. However when run as python3 5EE-Bluetooth-LED.py nothing happens. Why would that be abd what is needed to run as python3?
2. When this program is ran in Thonny, nothing happens either but I suspect that is because there too python3 is ran. Is that so, and how can this be solved?

When run as python3, the screen output is (after having entered first a "1" and then a "0" in the terminal:

Hello World

debug 1

debug 2

debug 3

debug 4

Accepted connecion from ('18:94:c6:95:de:0d', 1)

Received: b'1'

Received: b'0'

print("Hello World")
import bluetooth
import RPi.GPIO as GPIO        #calling for header file which helps in using GPIOs of PI
LED=21
GPIO.setmode(GPIO.BCM)     #programming the GPIO by BCM pin numbers. (like PIN40 as GPIO21)
GPIO.setwarnings(False)
GPIO.setup(LED,GPIO.OUT)  #initialize GPIO21 (LED) as an output Pin
GPIO.output(LED,0)
print("debug 1")
server_socket=bluetooth.BluetoothSocket( bluetooth.RFCOMM )
port = 0
print("debug 2")
server_socket.bind(("",port))
print("debug 3")
server_socket.listen(1)
print("debug 4")
client_socket,address = server_socket.accept()
print ("Accepted connection from ",address)
while 1:
 
   data = client_socket.recv(1024)
   print ("Received: %s" % data)
   if data == "0":    #if '0' is sent from the Android App, turn OFF the LED
        print ("GPIO 21 LOW, LED OFF")
        GPIO.output(LED,0)
   if data == "1":    #if '1' is sent from the Android App, turn OFF the LED
        print ("GPIO 21 HIGH, LED ON")
        GPIO.output(LED,1)
   if data == "q":
        print ("Quit")
        break
 
client_socket.close()
server_socket.close()

Answer 1

In python2: b"0" == u"0"

In python3: b"0" != u"0"

So your if statements don't match.

Probably best to do:

if data == "0":    #if '0' is sent from the Android App, turn OFF the LED
    print ("GPIO 21 LOW, LED OFF")
    GPIO.output(LED,0)
elif data == "1":    #if '1' is sent from the Android App, turn OFF the LED
    print ("GPIO 21 HIGH, LED ON")
    GPIO.output(LED,1)
elif data == "q":
    print ("Quit")
    break
else:
    print("Unknown command: "+repr(data))

Then you'll be able to work out a bit more about what's happening.

Answer 2

https://sebastianraschka.com/Articles/2014_python_2_3_key_diff.html

Very trivial, and the change in the print-syntax is probably the most widely known change, but still it is worth mentioning: Python 2’s print statement has been replaced by the print() function, meaning that we have to wrap the object that we want to print in parantheses.

Python 2 doesn’t have a problem with additional parantheses, but in contrast, Python 3 would raise a SyntaxError if we called the print function the Python 2-way without the parentheses.

Python 2 print 'Python', python_version() print 'Hello, World!' print('Hello, World!') print "text", ; print 'print more text on the same line' Python 2.7.6 Hello, World! Hello, World! text print more text on the same line Python 3 print('Python', python_version()) print('Hello, World!')

print("some text,", end="") print(' print more text on the same line') Python 3.4.1 Hello, World! some text, print more text on the same line print 'Hello, World!' File "", line 1 print 'Hello, World!' ^ SyntaxError: invalid syntax Note:

Printing “Hello, World” above via Python 2 looked quite “normal”. However, if we have multiple objects inside the parantheses, we will create a tuple, since print is a “statement” in Python 2, not a function call.

print 'Python', python_version() print('a', 'b') print 'a', 'b' Python 2.7.7 ('a', 'b') a b

Hope this helps