Python 3 - Using subprocess module to execute java command line prompt

Question

I have a java program on my computer that has a command line api. If navigate to the appropriate folder in a command prompt, I can enter the command

java -cp p2.jar propokertools.cli.RunPQL

to make various poker calculations from a command prompt. I would like to be able to interact with this program through Python.

I've tried:

p = subprocess.check_output(['java', '-cp', 'p2.jar propokertools.cli.RunPQL'], cwd='C:\\Program Files\\PPTOddsOracle\\ui_jar')

but get this error:

File "C:\Python34\lib\subprocess.py", line 620, in check_output raise CalledProcessError(retcode, process.args, output=output) subprocess.CalledProcessError: Command '['java', '-cp p2.jar propokertools.cli.RunPQL']' returned non-zero exit status 1

I decided to be less ambitious and just try to figure out how to get Python to return my java version, but

p = subprocess.check_output(['java', '-version'])

and

p = subprocess.Popen(["java", "-version"], stdout=subprocess.PIPE)
p.stdout.read()

both returned empty byte strings, so I think I'm doing something very wrong. Any help would be greatly appreciated.

Heyyy... subprocess.Popen(["java", "-version"], stderr=subprocess.PIPE).communicate() does indeed return my Java version! Thanks! — Thomas
– Thomas, Commented Mar 29, 2015 at 16:57
to merge stdout/stderr: outtput = subprocess.check_output(['java', '-version'], stderr=subprocess.STDOUT) — jfs
– jfs, Commented Mar 29, 2015 at 21:50

Thomas · Accepted Answer · 2015-03-30 09:15:21Z

1

I figured it out. I was missing that 'p2.jar propokertools.cli.RunPQL' needed to be split up into separate arguments.

p = subprocess.check_output(['java', '-cp', 'p2.jar', 'propokertools.cli.RunPQL'], cwd='C:\\Program Files\\PPTOddsOracle\\ui_jar')

answered Mar 30, 2015 at 9:15

Thomas

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3 Comments

cdarke Over a year ago

I have found that you need separate arguments in a list if you have shell=False (the default).

Thomas Over a year ago

You're right. This also works: subprocess.check_output('java -cp p2.jar propokertools.cli.RunPQL', cwd='C:\\Program Files\\PPTOddsOracle\\ui_jar',shell=False)

jfs Over a year ago

@cdarke: you don't need it on Windows. Though you could do it for portability.

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