python script runs from command line but using subprocess gives error

Question

the following command line works and gives correct results

$ python maps2.py -i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0 -o=temp/CMIP3 -p=temp_001

but when the exact command is called, using the following subprocess module:

run=subprocess.Popen([sys.executable, 'maps2.py -i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0 -o=temp/CMIP3 -p=temp_001' ])

it gives the following error:

/usr/bin/python: can't open file 'maps2.py -i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0 -o=temp/CMIP3 -p=temp_001': [Errno 2] No such file or directory

what's the reason? the commands are exactly the same. Thank you for your help.

Andrew Clark · Accepted Answer · 2013-06-19 16:45:21Z

2

When using subprocess.Popen() the first argument should be a list with a separate entry for each argument to the process you want to run:

run=subprocess.Popen([sys.executable, 'maps2.py', '-i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0', '-o=temp/CMIP3', '-p=temp_001' ])

What you currently have would be the equivalent to running the following on the command line:

python 'maps2.py -i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0 -o=temp/CMIP3 -p=temp_001'

answered Jun 19, 2013 at 16:45

Andrew Clark

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Colonel Panic · Accepted Answer · 2013-06-19 16:52:51Z

1

In addition to F.J.'s answer, you can easily split the name of the executable from the arguments with shlex.split

mapsCommand = 'maps2.py -i=/media/babak/LaCie/necessary/visualisation/CMIP3_Babak/Temperature/bccr_bcm2_0 -o=temp/CMIP3 -p=temp_001'
fullCommand = [sys.executable]
fullCommand.extend(shlex.split(mapsCommand))
run=subprocess.Popen(fullCommand)

edited Jun 19, 2013 at 16:52

answered Jun 19, 2013 at 16:45

Colonel Panic

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