User input using C# then display python output to C#

Question

I'm sorry if this may be an existing question but I'm having a hard time to execute this.

I have this simple python code where it asks user to input a number and multiply it by 2.

userInput = int({sys.argv[1]})
pythonOutput = userInput * 2
print("The number passed is: ", pythonOutput)

What I want do is for the user to enter the number in C# Winforms then also display the result in C#. So, the number needed for userInput from python code will come from C# and then the output from python code will be displayed in C#

This is currently my C# code

        string pythonInterpreter = @"C:\Anaconda3\python.exe";
        var start = new ProcessStartInfo
        {
            FileName = pythonInterpreter,
            Arguments = string.Format($"\"{@"C:\Users\chesk\Desktop\Work Files\Project\Thermal Camera\PythonForC#\SimpleInputOutput.py"}\" {txtUserInput.Text}"),
            UseShellExecute = false,
            RedirectStandardOutput = true,
            RedirectStandardInput = true,
            RedirectStandardError = true,
            CreateNoWindow = true,
        };


        var result = "0";
        var error = "";
        using (Process process = Process.Start(start))
        {
            result = process.StandardOutput.ReadToEnd();
            error = process.StandardError.ReadToEnd();
            lblPythonOutput.Text = result;
            lblPythonOutputError.Text = error;
        }

EDIT:

I updated both my python and c# codes and I can now pass value in python using C# but when sending an integer, this error appeared.

Traceback (most recent call last): File"C:\Users\chesk\Desktop\Work Files\Project\Thermal Camera\PythonForC#\SimpleInputOutput.py", line 8, in userInput = int({sys.argv[1]}) TypeError: int() argument must be a string, a bytes-like object or a number, not 'set'

Final Edit: So, it turns out that the c# code is really working but I need to modify my python code. So here it is.

userInput = int(sys.argv[1])
pythonOutput = userInput * 2
print("The number passed is: ", pythonOutput)

Hope this will help someone!

Nice job on solving your problem. Just a thought. Did you consider making the communication socket based instead? This way you could run your python script as a service on your Winform startup. It would allow you to easily extend it to more complex data types and provide a bump in performance. — spyder1329
– spyder1329, Commented Dec 16, 2020 at 16:26
Is IronPython a communication socket? I'm kinda new to this so I just created the simplest way that I thought. — Cheska Abarro
– Cheska Abarro, Commented Dec 16, 2020 at 16:43

Roy Cohen · Accepted Answer · 2020-12-15 21:49:55Z

2

The C# code doesn't look to bad. I think the issue is with your python code, because it's asking for userinput. But you're already passing the number as a command line argument to your python script, so it doesn't need to ask for user input. Instead you should use the argument passed to the python script.

Here is an example:

import sys
print(f"The number passed by c# was: {sys.argv[1]}")

You can checkout this tutorial about python command line arguments for more information

Edits:

Changed sys.argv[0] to sys.argv[1] - Thanks Roy Cohen

Changed to f-strings - Thanks Roy Cohen

edited Dec 15, 2020 at 21:49

Roy Cohen

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answered Dec 15, 2020 at 21:06

AdrAs

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7 Comments

Cheska Abarro Over a year ago

Thank you for the answer! I tried the exact same code you mentioned above with the existing C# code but the StandartOutput still returns null.

Cheska Abarro Over a year ago

And an error appeared. It says Traceback (most recent call last): File "SimpleInputOutput.py", line 10, in <module> print(f"The number passed is: {sys.argv[1]}") IndexError: list index out of range

AdrAs Over a year ago

What is your current code? Can you edit your question?

Cheska Abarro Over a year ago

Hi AdrAs! I modified both my c3 and python codes and that made me able to pass data from c# to python and vice versa but encountered new error. Please see my updated code.

user5386938 Over a year ago

This is wrong: userInput = int({sys.argv[1]}). You should not have the curly braces {} there as they turn your string into a set.

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