CODEWITHSUNDEEP
pythonpython-3.x
martin_bluetooth_sig
martin_bluetooth_sig

Reputation: 381

Why is my python if block not entered when the conditions seem to be true?

I'm very new to Python... liking it but having a weird problem. Here's some code:

    def run(self):
        print("receiver starting")
        while self.receiving:
            print("RX loop")
            try:
                print("RX: waiting for PDU from peer")
                data, addr = self.rx_socket.recvfrom(32)
                print("RX: received %d bytes"%(len(data)))
                print("RX: self.receiving=%d"%(self.receiving))
                print("XXXX RX: 0x%s"%(data.hex()))

                # condition seems to be true but block not entered
                if self.receiving == 1 & len(data) > 0:
                    my_pdu = 0
                    print("ZZZZ RX: 0x%s"%(data.hex()))

As you can see, I have a loop running in a thread which reads from a socket. Now look at this test output:

RX loop
RX: waiting for PDU from peer
RX: received 3 bytes
RX: self.receiving=1
XXXX RX: 0x022000
ZZZZ RX: 0x022000
RX loop
RX: waiting for PDU from peer
RX: received 8 bytes
RX: self.receiving=1
XXXX RX: 0x100100ffff020028
RX loop
RX: waiting for PDU from peer

My first read returns 3 bytes and we see both the XXXX prefixed print statement outside the if block and then the ZZZZ prefixed statement inside the if block, as expected.

The second read returns 8 bytes, prints the XXXX prefixed line but then does not enter the if block despite the condition (self.receiving == 1 & len(data) > 0) both being true according to the printed values prior to the XXXX line.

My thread isn't exiting otherwise I wouldn't see the "RX loop" line again.

Can any of you experienced Python people tell me what I've done wrong here?

Thank you

Upvotes: 0

Views: 129

Answers (3)

jDo
jDo

Reputation: 4010

Since you can write while self.receiving:, I presume it's a booolean; this means that you can just write if self.receiving.

& is the binary/bitwise and operator and it's probably not what you want here. I think you're after and.

Try changing

if self.receiving == 1 & len(data) > 0:

to

if self.receiving and len(data) > 0:

Upvotes: 1

SpoonMeiser
SpoonMeiser

Reputation: 20457

The problem is that & is bitwise and, and you want logical and, which is and:

if self.receiving == 1 and len(data) > 0:

Upvotes: 3

dquam
dquam

Reputation: 101

In Python, the boolean AND is just and not && or &.

Upvotes: 1

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