Mantaining a connection between C# and Python using stdout

Question

I'm trying to maintain a connection between a C# and a Python script. I want to read the output from python at the same moment it is printed, but I can do it once the python script is finished, not during its execution.

Here is the C# program, which read asynchronously the stdout stream.

using System;
using System.Diagnostics;

namespace PruebaConnexion
{
    class Program
    {
        static void Main(string[] args)
        {
            ProcessStartInfo start = new ProcessStartInfo();
            start.FileName = "D:\\Programas\\Anaconda\\python.exe";
            start.Arguments = ".\\PythonScript.py";
            start.UseShellExecute = false;
            start.RedirectStandardOutput = true;
            // start.RedirectStandardInput = true;

            Process process = Process.Start(start);
            process.OutputDataReceived += new DataReceivedEventHandler((sender, e) =>
            {
                Console.WriteLine("Hello "+e.Data);
            });

            process.BeginOutputReadLine();

            while (true)
            {}
            
        }
    }
}

And here is the python code:

import time
import sys

for i in range(10):
    time.sleep(1)

    sys.stdout.write("OK")

I also tried with print, instead of sys.stdout.write. I get printed on C#:

Hello OKOKOKOKOKOKOKOKOKOK

But what I need is:

Hello OK
Hello OK
Hello OK
.
.

One Hello OK per second, but not all of them at the same time.

score 0 · Answer 1 · answered Oct 15 '20 at 09:16

0

I also tried with print, instead of sys.stdout.write. I get printed on C#:

I tested with sys.stdout.write and got same result, but it worked as expected with print. I am using python3 on WSL. I also got it to work like this:

sys.stdout.write("OK\n")

So it seems like c# will read the data line by line

answered Oct 15 '20 at 09:16

toftis

1,070
9
26

Yes, you get that output but not 1 every second. It prints 10 ```Hello OK``` at the same time. – Javier Jiménez de la Jara Oct 15 '20 at 09:25
1

[sys.stdout.flush()](https://stackoverflow.com/questions/10019456/usage-of-sys-stdout-flush-method/10019605) might help. – Axel Kemper Oct 15 '20 at 09:36
It worked!! Thank you so much, flush forces python to write on stream. – Javier Jiménez de la Jara Oct 15 '20 at 09:43

Mantaining a connection between C# and Python using stdout

1 Answers1