Python string comparison

Question

Hello all,

I have a python function that makes a subprocess call to a shell script that outputs 'true' or 'false'. I'm storing the output from subprocess.communicate() and trying to do return output == 'true' but it returns False every time. I'm not too familiar with python, but reading about string comparisons says you can compare strings using ==, !=, etc.

Here's the code:

def verifydeployment(application):
    from subprocess import Popen, PIPE
    import socket, time

    # Loop until jboss is up.  After 90 seconds the script stops looping; this
    # causes twiddle to be unsuccessful and deployment is considered 'failed'.
    begin = time.time()
    while True:
        try:
            socket.create_connection(('localhost', 8080))
            break
        except socket.error, msg:
            if (time.time() - begin) > 90:
                break
            else:
                continue

    time.sleep(15)  # sleep for 15 seconds to allow JMX to initialize

    twiddle = os.path.join(JBOSS_DIR, 'bin', 'twiddle.sh')
    url = 'file:' + os.path.join(JBOSS_DIR, 'server', 'default', 'deploy', os.path.basename(application))

    p = Popen([twiddle, 'invoke', 'jboss.system:service=MainDeployer', 'isDeployed', url], stdout=PIPE)
    isdeployed = p.communicate()[0]

    print type(isdeployed)
    print type('true')
    print isdeployed
    return isdeployed == 'true'

The output is:

<type 'str'> # type(isdeployed)
<type 'str'> # type('true')
true         # isdeployed

but False is always returned. I also tried return str(isdeployed) == 'true'.

Answer 1

Are you sure that there isn't a terminating line feed character, making your string contain "true\n"? That seems likely.

You could try return isdeployed.startswith("true"), or some stripping.

Answer 2

Have you tried to call

isdeployed.strip()

before the comparision