Need to assign the result of a command line that runs another .py file to a Variable in Python, but modify the command as needed within the code

Question

I need to assign the result of the following command line to a variable:

!python script.py –img_file ../data/img.png

The catch is that I need to run this within a for loop and change the path "../data/img.png" to "../data/img2.png", "../data/img3.png", etc. based on the loops.

A snippet of the code that does not work but shows the idea:

for i in range(len(uppers)):    
        cv2.imwrite('data/img' + str(img_num) + '.png', img[uppers[i]:lowers[i],:])
        img_var = !python script.py --img_file ../data/img+str(img_num).png
        img_num += 1

Appreciate any help or thoughts.

Asked By: DJMB

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Source

Answer 1

You can achieve this by building the command as a string and passing it to the subprocess module’s run() method. Here’s an example:

import subprocess

img_num = 1
for i in range(len(uppers)):    
    cv2.imwrite('data/img' + str(img_num) + '.png', img[uppers[i]:lowers[i],:])
    img_path = '../data/img' + str(img_num) + '.png'
    command = ['python', 'script.py', '--img_file', img_path]
    result = subprocess.run(command, capture_output=True, text=True)
    img_var = result.stdout
    img_num += 1

We pass the capture_output=True parameter to capture both the standard output and the standard error streams, and the text=True parameter to get the output as a string instead of bytes.

The img_path variable is created inside the loop to update the image file path based on the loop counter. The img_var variable will contain the output of the script for each loop iteration. You can then process this output as needed.

Answered By: Kadam

Need to assign the result of a command line that runs another .py file to a Variable in Python, but modify the command as needed within the code

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