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I am having difficulties running a series of sequential commands using the subprocess module, i need to do this so a python program can call in an installation of a cv virtualenv and then run another python program (that needs to be run within the virtualenv)

This is the command string i run from terminal, you can see it contains multiple commands that run in sequence until the creation of the cv virtual env:

sudo pip install virtualenv virtualenvwrapper && sudo rm -rf ~/.cache/pip && export WORKON_HOME=$HOME/.virtualenvs && source /usr/local/bin/virtualenvwrapper.sh && source ~/.bashrc && mkvirtualenv cv

Running this in the terminal returns me something like this:

(cv) name@computer:~$

from that i can run my python scripts that need the openCV

my code so far is this:

from subprocess import Popen, PIPE, STDOUT

cmd1 = 'sudo pip install virtualenv virtualenvwrapper'
cmd2 = 'sudo rm -rf ~/.cache/pip'
cmd3 = 'export WORKON_HOME=$HOME/.virtualenvs'
cmd4 = 'source /usr/local/bin/virtualenvwrapper.sh'
cmd5 = 'source ~/.bashrc'
cmd6 = 'mkvirtualenv cv'
cmd7 = 'cd /script path'
cmd8 = 'python novo.py'


final = Popen("{}; {}; {}; {}; {}; {}; {}; {}".format(cmd1, cmd2,cmd3,    cmd4, cmd5, cmd6, cmd7, cmd8), shell=True, stdin=PIPE, 
      stdout=PIPE, stderr=STDOUT, close_fds=True)

stdout, nothing = final.communicate()
log = open('log', 'w')
log.write(stdout)
log.close()

And the errors in log look like this:

/bin/sh: 1: source: not found
/bin/sh: 1: source: not found
/bin/sh: 1: mkvirtualenv: not found

How can i achieve a terminal like execution ? again, sequence is crucial.

dimo414
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Douglas Heydt
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1 Answers1

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/bin/sh: 1: source: not found

shell=True uses /bin/sh by default. source shell builtin hints at bash. Pass executable='/bin/bash'.

btw, you could use a multiline string literal:

#!/usr/bin/env python3
import sys
from subprocess import check_call, DEVNULL, STDOUT

with open('log', 'wb', 0) as file:
   check_call("""set -e -x
{python} -mpip install --user virtualenv virtualenvwrapper
rm -rf ~/.cache/pip
export WORKON_HOME=$HOME/.virtualenvs
source /path/to/virtualenvwrapper.sh
source ~/.bashrc
mkvirtualenv cv
cd /script path
{python} novo.py
""".format(python=sys.executable),
              shell=True, executable='/bin/bash',
              stdin=DEVNULL, stdout=file, stderr=STDOUT, close_fds=True)

Or save the command into a separate bash script and run the script instead.

DEVNULL is Python 3 feature—it is easy to emulate it on Python 2 too: DEVNULL = open(os.devnull, 'r+b', 0).

Community
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jfs
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  • Hello J.F. Sebastian, thank you for your answer, i changed the code on my python script as you suggested, but now when i execute it gives an error "File "programa.py", line 3, in from subprocess import check_call, DEVNULL, STDOUT ImportError: cannot import name DEVNULL" i am really new to this kind of operations, my knowledge stays on python and opencv, dont know how to properly work with this kind of calls and bash files. – Douglas Heydt May 26 '16 at 15:53
  • i dont really understand how shebangs work but i changed it to pyhton2, it returns a 'CalledProcessError', you can check out the code and error on this image if it not too much trouble http://postimg.org/image/f6dfdaucr/ – Douglas Heydt May 26 '16 at 16:18
  • My answer fixes one issue: `source: not found`. If you have another issue; you should ask it as a separate question. – jfs May 26 '16 at 16:22