Python Forum

Hello,

Out of curiosity, is this the simplest way in Python3 to run an external command-line application with parameters?

Thank you.

from subprocess import Popen, PIPE
import shlex

command_line = "command -a 50 -o %03d.jpg input.doc"
args = shlex.split(command_line)
args.insert(0, r"C:\app.exe")
process = Popen(args,stdout=PIPE, stderr=PIPE)

stdout, stderr = process.communicate()

print(stdout)

maybe can you try something like:

import subprocess, os, sys
command_line = subprocess.Popen('command -a 50 -o %03d.jpg input.doc', 
                                 shell = True, 
                                 stdin = None, 
                                 stdout = subprocess.PIPE) 
run = subprocess.Popen('C:\app.exe', 
                       stdin = command_line.stdout, 
                       stdout = subprocess.PIPE)
result = run.communicate() 
print(result)
run.wait()
sys.stdout.flush() 

A advice subprocess.run should be used with all cases it can handle.
Subprocess Doc

Quote:The recommended approach to invoking subprocesses is to use the run() function for all use cases it can handle.
For more advanced use cases, the underlying Popen interface can be used directly.

Can also use capture_output=True,and no need top use args.insert as see f-string dos this fine.

import subprocess

output_file = "%03d.jpg"
input_file = "input.doc"
executable_path = r"C:\app.exe"
command_line = f"{executable_path} command -a 50 -o {output_file} {input_file}"
args = command_line.split()
result = subprocess.run(args, encoding='utf-8', capture_output=True)
print(result.stdout)