SoFunction
Updated on 2025-03-02

Demo of Popen function in Python

1. Basic knowledge

In Python, Popen is a function in the subprocess module that is used to create and communicate with a child process

  • (): The Popen class is used to create and manage child processes

Popen provides more flexibility, such as reading standard output and standard errors of child processes than () or ()
Parameter description:
exe_path: The executable file or command to be executed
stderr=PIPE: Redirects the standard error of the child process to the pipeline so that the parent process can catch
stdout=PIPE: (optional) Standard output can be redirected

  • ()：

communicate() is used to interact with child processes. It waits for the child process to complete execution and returns a tuple containing standard output and standard errors
After calling communicate(), the input and output stream of the child process will be closed.

  • stderr and stdout：

stderr: Records the standard error output of the child process, usually containing error information encountered during execution
stdout: Contains the standard output of the child process, that is, the result after executing the command

Specific call method:

import subprocess
# Example: Open a child process to execute exe using Popenexe_path = "path_to_executable.exe"  # Replace with the actual executable file pathexe = (exe_path, stdout=, stderr=)
# Interact with the child process and wait for it to completestdout, stderr = ()
# Print standard output and error outputprint("Standard Output:", ('utf-8'))
print("Standard Error:", ('utf-8'))

1. Promoter process: Use Popen to start the specified executable file exe_path
This process runs in the background and the parent process will not be blocked

2. Capture the output: Through the stderr=PIPE parameter, the error information of the child process can be captured
You can also capture stdout=PIPE to get the execution result

3. Process the results of child processes: Call communicate(), which blocks until the child process completes running
The returned stdout and stderr are byte streams, so they need to be converted to strings via decode('utf-8')

2. Demo

Suppose there is a simple executable file, which can be called as follows:

import subprocess
# Executable file pathexe_path = ""
# Launch child process, capture standard output and standard errorsexe = ([exe_path], stdout=, stderr=)
# Interact with child processesstdout, stderr = ()
# Printout and errorsif stdout:
    print("Standard Output:", ('utf-8'))
if stderr:
    print("Standard Error:", ('utf-8'))

Frequently Asked Questions

  • The child process is stuck: If the child process produces a large amount of output and is not processed in time, the pipeline may be filled, causing the child process to hang

In this case, you can consider manually reading the stream

  • Capture real-time output: If you need to read the output of the child process in real time instead of waiting until communicate() returns, you can loop to read stdout

This is all about this article about Popen functions in Python. For more related Python Popen functions, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!