What’s The Difference Between Subprocess Popen And Call

subprocess.Popen and subprocess.call are both functions provided by the Python subprocess module for running external commands or processes from within a Python script. However, they have different use cases and behavior:

subprocess.call:

subprocess.call is a simple way to run an external command and wait for it to complete. It takes a command as an argument and runs it in a new process, blocking the execution of the Python script until the command finishes.

It returns the return code of the executed command. The return code can be used to determine whether the command was successful or not.

Example:

import subprocess
result = subprocess.call(["ls", "-l"])
Code language: Python (python)

• In this example, the ls -l command is executed, and the return code is stored in the result variable. The script waits for the ls command to finish before continuing.

subprocess.Popen:

• subprocess.Popen is a more flexible way to run external commands. It creates a new process, but unlike subprocess.call, it doesn’t block the execution of the Python script. Instead, it returns a Popen object that represents the running process.
• You can use methods of the Popen object to interact with the running process, such as reading its output, sending input, or waiting for it to finish.

Example:

import subprocess
process = subprocess.Popen(["ls", "-l"], stdout=subprocess.PIPE)
output, error = process.communicate()
Code language: Python (python)

• In this example, the ls -l command is executed, and its output is captured in the output variable. The script can continue running other tasks while the ls command runs.

When To Use These?

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Use subprocess.call when:

• You want to run an external command synchronously, and your script should wait for the command to complete before proceeding.
• You simply need to execute a command and get its return code to check whether it was successful or not.
• You have a simple use case where you don’t need to capture the command’s output or interact with it further.

Use subprocess.Popen when:

• You want to run an external command asynchronously, allowing your script to continue executing other tasks while the command runs in the background.
• You need to capture the output (stdout and/or stderr) of the command.
• You want to interact with the running process, such as sending input to it or waiting for it to finish.
• You need more control over the behavior of the external process.

You would use subprocess.call when you want to run an external command and wait for it to finish before proceeding with your script, and you would use subprocess.Popen when you need more control over the execution of the external command, such as capturing its output, sending input, or running it in the background while your script continues to execute other tasks.

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