Python Subprocess Run In Background [With Example]

Yes, you can run a Python subprocess in the background just like any other external command.

To run a Python script as a background process, you can use the subprocess module, and the general process is the same as running any other command in the background.

To run a subprocess in the background, you typically need to do the following:

1. Import the subprocess module.
2. Use the subprocess.Popen class to start the subprocess with the stdout, stderr, and stdin streams set to subprocess.PIPE or None.
3. Use the Popen object’s communicate() method to interact with the subprocess if needed.
4. Optionally, use the Popen object’s wait() method to wait for the subprocess to finish.

Here’s an example of running a subprocess in the background:

import subprocess

# Define the command to run as a list of arguments
command = ["python", "my_script.py", "arg1", "arg2"]

# Start the subprocess in the background
process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)

# You can communicate with the subprocess if needed
# For example, sending data to stdin and reading from stdout/stderr
process.stdin.write(b"input_data\n")
process.stdin.flush()

output, error = process.communicate()

# Optionally, wait for the subprocess to finish
# process.wait()

# Print the output and error (if any)
print("Output:", output.decode())
print("Error:", error.decode())
Code language: Python (python)

In this example, replace "python", "my_script.py", "arg1", and "arg2" with the actual command and arguments you want to run.

The communicate() method is used to send data to the subprocess’s stdin and collect its output and error streams.

If you don’t need to interact with the subprocess, you can simply omit the stdin, stdout, and stderr parameters when creating the Popen object.

How to run a background process and don’t wait?

To run a background process in Python and not wait for it to finish, you can use the subprocess.Popen class and then simply not call the wait() method.

By not waiting for the process to finish, your Python script can continue running other tasks while the background process runs independently. Here’s an example:

import subprocess

# Define the command to run as a list of arguments
command = ["python", "my_script.py", "arg1", "arg2"]

# Start the subprocess in the background
process = subprocess.Popen(command)

# Your script can continue executing other tasks here

# Optionally, you can wait for the subprocess to finish if needed
# process.wait()
Code language: Python (python)

In this example, the subprocess.Popen function starts the subprocess and immediately returns control to your script without waiting for the subprocess to complete.

You can continue executing other tasks in your Python script while the background process runs independently.

If you want to wait for the background process to finish at some point, you can uncomment the process.wait() line.

Keep in mind that if you don’t wait for the background process to finish, you won’t be able to capture its output or error messages using the communicate() method, as shown in the previous response.

If you need to capture the output or interact with the background process, you should consider using methods like piping or redirection to save the output to a file or another stream, and then read from it asynchronously in your Python script.

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