No output when trying to run a shell command from python

Question

I've never created PowerShell script or anything like that so that's why I'm trying to run the command from Python instead since I thought all I have to do is just called it using the os.popen() command.

I have over 5000 folders all containing images that I'm going to extract keypoints from using a script that I've downloaded from github.

When I tried running my Python script nothing shows up. There's a window containing the image with the keypoints that is supposed to show up when I run the command but nothing shows up.

I have tried the command in PowerShell on one folder and it works perfectly.

Here's my script:

import os
import sys
import time

os.chdir(
    r"C:\Users\Adam\Downloads\openpose-1.7.0-binaries-win64-cpu-python3.7-flir-3d\openpose"
)
for root, dirs, files in os.walk(
    r"C:\Users\Adam\Downloads\LIP_MPV_256_192\MPV_256_192\all\all\images\train"
):
    for d in dirs:
        print("got here")
        os.popen(
            "bin\\OpenPoseDemo.exe --image_dir"
            + " C:\\Users\\Adam\\Downloads\\LIP_MPV_256_192\\MPV_256_192\\all\\all\\images\\train\\"
            + d
            + "--write_json"
            + " C:\\Users\\Adam\\Downloads\\LIP_MPV_256_192\\MPV_256_192\\all\\all\\images\\pose_coco\\train\\"
            + d
        )
        time.sleep(5)

The os.chdir() seems dubious; does the binary not work if you are not in that directory? — tripleee
– tripleee, Commented May 4, 2021 at 8:15

tripleee · Accepted Answer · 2021-05-04 08:14:16Z

1

You could try with subprocess module from the Python standard library:

import os
import subprocess
import time

os.chdir(
    r"C:\Users\Adam\Downloads\openpose-1.7.0-binaries-win64-cpu-python3.7-flir-3d\openpose"
)
for root, dirs, files in os.walk(
    r"C:\Users\Adam\Downloads\LIP_MPV_256_192\MPV_256_192\all\all\images\train"
):
    for d in dirs:
        print("got here")
        command = [
            "bin\\OpenPoseDemo.exe",
            "--image_dir",
            " C:\\Users\\Adam\\Downloads\\LIP_MPV_256_192\\MPV_256_192\\all\\all\\images\\train\\" + d,
            "--write_json",
            " C:\\Users\\Adam\\Downloads\\LIP_MPV_256_192\\MPV_256_192\\all\\all\\images\\pose_coco\\train\\"
            + d
        ]
        subprocess.run(args=command, shell=False, capture_output=True)
        time.sleep(5)

edited May 4, 2021 at 8:14

tripleee

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answered May 4, 2021 at 6:46

Laurent

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3 Comments

tripleee Over a year ago

With shell=False the command should be a list, not a string. Windows is less sensitive to this, but breaking up the command line to a list of tokens is also less error-prone.

tripleee Over a year ago

subprocess.run is definitely the way to go, though perhaps it could be mentioned that os.popen() is (now) just an alias for subprocess.Popen(). Using the higher-level run() function is absolutely recommended, unless you need behavior which run cannot accommodate, such as parallel processing (and then you need to do a fair bit of additional housekeeping around the subprocess which run takes care of for you).

Laurent Over a year ago

@triplee Indeed, I have corrected my answer. Also, thank you for these clarifications and additional information.

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