Effortlessly Set Up Pipe Communication Between Python and C+ +

Struggling with inter-process communication between Python and C+ + ? Discover how to effectively establish pipe communication and troubleshoot common errors.
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This video is based on the question https://stackoverflow.com/q/69471964/ asked by the user 'Markos Othonos' ( https://stackoverflow.com/u/17092437/ ) and on the answer https://stackoverflow.com/a/69472193/ provided by the user 'Ted Lyngmo' ( https://stackoverflow.com/u/7582247/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Effortlessly Set Up Pipe Communication Between Python and C+ +

Inter-process communication (IPC) is a crucial mechanism that allows multiple programs to communicate with one another. When working with Python and C+ + , you might encounter difficulties in establishing this communication, especially when using pipes. This post dives deep into how to set up pipe communication between Python and C+ + , highlighting common pitfalls and their respective solutions.

The Problem

You’re trying to create a communication link between a Python and a C+ + process using pipes on a Ubuntu WSL environment. While your code compiles without errors, you're not receiving any messages on either end. The output shows that while the pipes are being called, the expected message transfer is failing. This leads you to wonder what could possibly be going wrong.

Understanding the Code

Before we jump into the solution, let’s break down the provided code snippets to understand what is happening in both the Python (test.py) and C+ + (test.cpp) files.

Python Code Breakdown

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C+ + Code Breakdown

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Diagnosing the Issues

From the description of your issue, a few critical points stand out:

File Descriptor Issues: The core issue stems from the fact that the file descriptors (pipes) do not get inherited by the child process (the C+ + executable). As a result, the C+ + program ends up trying to read from closed descriptors, resulting in communication failure.

Undefined Behavior: There may also be issues with reading or writing to buffers beyond their allocated sizes, which could lead to undefined behavior in C+ + . In the C+ + code, remember to handle the buffer carefully to avoid reading and writing out of bounds.

Proposed Solutions

To resolve the issue, you can follow these steps:

1. Set Inheritance Mode

You need to ensure that the file descriptors are inheritable when going from Python to C+ + . You can do this using the following code snippet:

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2. Use os.pipe2 for Inheritable Pipes

An alternative way to create inheritable pipes is to use the os.pipe2(0) function, which automatically sets the inheritance.

3. Modify Subprocess Call

When calling the C+ + subprocess, ensure not to close the FDs before they are passed to the subprocess. Use the close_fds=False option:

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Conclusion

By following the steps outlined above, you can successfully establish inter-process communication between Python and C+ + . Debugging IPC can be tricky, but with careful management of file descriptors and system calls, you’ll become adept at navigating and resolving common issues.

Feel free to try out these tips in your code, and watch the messages flow seamlessly between your Python script and C+ + application.