How do I run a Python script from C#?

Question

This sort of question has been asked before in varying degrees, but I feel it has not been answered in a concise way and so I ask it again.

I want to run a script in Python. Let's say it's this:

if __name__ == '__main__':
    f = open(sys.argv[1], 'r')
    s = f.read()
    f.close()
    print s

Which gets a file location, reads it, then prints its contents. Not so complicated.

Okay, so how do I run this in C#?

This is what I have now:

    private void run_cmd(string cmd, string args)
    {
        ProcessStartInfo start = new ProcessStartInfo();
        start.FileName = cmd;
        start.Arguments = args;
        start.UseShellExecute = false;
        start.RedirectStandardOutput = true;
        using (Process process = Process.Start(start))
        {
            using (StreamReader reader = process.StandardOutput)
            {
                string result = reader.ReadToEnd();
                Console.Write(result);
            }
        }
    }

When I pass the code.py location as cmd and the filename location as args it doesn't work. I was told I should pass python.exe as the cmd, and then code.py filename as the args.

I have been looking for a while now and can only find people suggesting to use IronPython or such. But there must be a way to call a Python script from C#.

Some clarification:

I need to run it from C#, I need to capture the output, and I can't use IronPython or anything else. Whatever hack you have will be fine.

P.S.: The actual Python code I'm running is much more complex than this, and it returns output which I need in C#, and the C# code will be constantly calling the Python.

Pretend this is my code:

    private void get_vals()
    {
        for (int i = 0; i < 100; i++)
        {
            run_cmd("code.py", i);
        }
    }

Answer 1

Set WorkingDirectory or specify the full path of the python script in the Argument

ProcessStartInfo start = new ProcessStartInfo();
start.FileName = "C:\\Python27\\python.exe";
//start.WorkingDirectory = @"D:\script";
start.Arguments = string.Format("D:\\script\\test.py -a {0} -b {1} ", "some param", "some other param");
start.UseShellExecute = false;
start.RedirectStandardOutput = true;
using (Process process = Process.Start(start))
{
    using (StreamReader reader = process.StandardOutput)
    {
        string result = reader.ReadToEnd();
        Console.Write(result);
    }
}

Answer 2

If you're willing to use IronPython, you can execute scripts directly in C#:

using IronPython.Hosting;
using Microsoft.Scripting.Hosting;

private static void doPython()
{
    ScriptEngine engine = Python.CreateEngine();
    engine.ExecuteFile(@"test.py");
}

Get IronPython here.

Answer 3

I am having problems with stdin/stout - when payload size exceeds several kilobytes it hangs. I need to call Python functions not only with some short arguments, but with a custom payload that could be big.

A while ago, I wrote a virtual actor library that allows to distribute task on different machines via Redis. To call Python code, I added functionality to listen for messages from Python, process them and return results back to .NET. Here is a brief description of how it works.

It works on a single machine as well, but requires a Redis instance. Redis adds some reliability guarantees - payload is stored until a worked acknowledges completion. If a worked dies, the payload is returned to a job queue and then is reprocessed by another worker.

Answer 4

The reason it isn't working is because you have UseShellExecute = false.

If you don't use the shell, you will have to supply the complete path to the python executable as FileName, and build the Arguments string to supply both your script and the file you want to read.

Also note, that you can't RedirectStandardOutput unless UseShellExecute = false.

I'm not quite sure how the argument string should be formatted for python, but you will need something like this:

private void run_cmd(string cmd, string args)
{
     ProcessStartInfo start = new ProcessStartInfo();
     start.FileName = "my/full/path/to/python.exe";
     start.Arguments = string.Format("{0} {1}", cmd, args);
     start.UseShellExecute = false;
     start.RedirectStandardOutput = true;
     using(Process process = Process.Start(start))
     {
         using(StreamReader reader = process.StandardOutput)
         {
             string result = reader.ReadToEnd();
             Console.Write(result);
         }
     }
}

Answer 5

Just also to draw you attention to this:

https://code.msdn.microsoft.com/windowsdesktop/C-and-Python-interprocess-171378ee

It works great.

Answer 6

I ran into the same problem and Master Morality's answer didn't do it for me. The following, which is based on the previous answer, worked:

private void run_cmd(string cmd, string args)
{
 ProcessStartInfo start = new ProcessStartInfo();
 start.FileName = cmd;//cmd is full path to python.exe
 start.Arguments = args;//args is path to .py file and any cmd line args
 start.UseShellExecute = false;
 start.RedirectStandardOutput = true;
 using(Process process = Process.Start(start))
 {
     using(StreamReader reader = process.StandardOutput)
     {
         string result = reader.ReadToEnd();
         Console.Write(result);
     }
 }
}

As an example, cmd would be @C:/Python26/python.exe and args would be C://Python26//test.py 100 if you wanted to execute test.py with cmd line argument 100. Note that the path the the .py file does not have the @ symbol.