How to make a call to an executable from Python script?

Question

I need to execute this script from my Python script.

Is it possible? The script generate some outputs with some files being written. How do I access these files? I have tried with subprocess call function but without success.

fx@fx-ubuntu:~/Documents/projects/foo$ bin/bar -c somefile.xml -d text.txt -r aString -f anotherString >output

The application "bar" also references to some libraries, it also create the file "bar.xml" besides the output. How do I get access to these files? Just by using open()?

Thank you,

Edit:

The error from Python runtime is only this line.

$ python foo.py
bin/bar: bin/bar: cannot execute binary file

subprocess is what you need to use, can you provide an example so we have a better idea why it didn't work? — Kaleb Pederson
– Kaleb Pederson, Commented Mar 18, 2010 at 22:08
"subprocess call"? What is that? Please post the code you used and the error you actually got. — S.Lott
– S.Lott, Commented Mar 18, 2010 at 22:51
Yes, he's talking about the "call" function in the standard "subprocess" module, which is the better way to do this, although os.system may be adequate depending on his needs — Peter Lyons
– Peter Lyons, Commented Mar 19, 2010 at 1:37

Peter Lyons · Accepted Answer · 2010-03-19 01:47:04Z

47

For executing the external program, do this:

import subprocess
args = ("bin/bar", "-c", "somefile.xml", "-d", "text.txt", "-r", "aString", "-f", "anotherString")
#Or just:
#args = "bin/bar -c somefile.xml -d text.txt -r aString -f anotherString".split()
popen = subprocess.Popen(args, stdout=subprocess.PIPE)
popen.wait()
output = popen.stdout.read()
print output

And yes, assuming your bin/bar program wrote some other assorted files to disk, you can open them as normal with open("path/to/output/file.txt"). Note that you don't need to rely on a subshell to redirect the output to a file on disk named "output" if you don't want to. I'm showing here how to directly read the output into your python program without going to disk in between.

answered Mar 19, 2010 at 1:47

Peter Lyons

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2 Comments

fx. Over a year ago

Hi Peter, there is the error: bin/bar: bin/bar: cannot execute binary file and without any other information from the Python runtime. What is the cause?

fx. Over a year ago

it's about the executable's error. I have solved it, thanks Peter.

rz. · Accepted Answer · 2010-03-18 22:17:18Z

20

The simplest way is:

import os
cmd = 'bin/bar --option --otheroption'
os.system(cmd) # returns the exit status

You access the files in the usual way, by using open().

If you need to do more complicated subprocess management then the subprocess module is the way to go.

answered Mar 18, 2010 at 22:17

rz.

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2 Comments

Brian McCutchon Over a year ago

Note that this has the same security caveat as subprocess.Popen(shell=True). Don't use it with anything other than a literal string.

Timo Over a year ago

I want to execute tesseract on every file in my folder, so I os.walk and then do the progr in the loop. How does it work?

Community · Accepted Answer · 2023-05-23 18:50:58Z

9

For executing a unix executable file. I did the following in my Mac OSX and it worked for me:

import os
cmd = './darknet-classifier-predict-data/baby.jpg'
so = os.popen(cmd).read()
print(so)

Here print(so) outputs the result.

edited May 23, 2023 at 18:50

CommunityBot

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answered Jun 4, 2018 at 10:28

Sumesh Chandran

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Comments

ms-afk · Accepted Answer · 2025-03-27 20:58:54Z

0

In Python 3.5 and higher¹ you can use subprocess.run to do what Peter's answer does in less code:

import subprocess
args = ("bin/bar", "-c", "somefile.xml", "-d", "text.txt", "-r", "aString", "-f", "anotherString")
subprocess = subprocess.run(args, capture_output=True)
print(subprocess.stdout)

See this answer to understand the difference between the two functions.

¹: For reading and saving the output of the command, the example above makes use of the capture_output=True flag, which was only added in Python 3.7.
In previous versions you will have to use subprocess.run(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE) to achieve the same result.

edited Mar 27 at 20:58

answered Mar 27 at 17:07

ms-afk

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1 Comment

Barmar Mar 27 at 17:31

It was added in 3.5, not 3.7.

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