[Python.NET] Embedding a Python interactive shell in a .NET application
Cameron Hayne
cameron.hayne at introspect.ca
Fri May 27 18:15:40 EDT 2016
I’m using a similar method for redirecting Python output to a .NET textBox:
#----------------------------------------------------------
public static void redirectPythonOutput(TextWriter writer)
{
Output output = new Output(writer);
using (Py.GIL())
{
dynamic sys = Py.Import("sys");
sys.stdout = output;
sys.stderr = output;
}
}
#----------------------------------------------------------
where ‘Output’ is my own .NET class that implements the method expected of a Python file object:
#----------------------------------------------------------
public class Output
{
private TextWriter myWriter = null;
// ctor
public Output(TextWriter writer)
{
myWriter = writer;
}
public void write(String str)
{
str = str.Replace("\n", Environment.NewLine);
if (myWriter != null)
{
myWriter.Write(str);
}
else
{
Console.Write(str);
}
}
public void writelines(String[] str)
{
foreach (String line in str)
{
if (myWriter != null)
{
myWriter.Write(str);
}
else
{
Console.Write(str);
}
}
}
public void flush()
{
if (myWriter != null)
{
myWriter.Flush();
}
}
public void close()
{
if (myWriter != null)
{
myWriter.Close();
}
}
}
#----------------------------------------------------------
and I pass an instance of my TextBoxStreamWriter class to the constructor of Output:
#----------------------------------------------------------
public class TextBoxStreamWriter : TextWriter
{
TextBox myTextBox = null;
// ctor
public TextBoxStreamWriter(TextBox textBox)
{
myTextBox = textBox;
}
// TODO: isn't this inefficient? Should we supply a method to write a string?
public override void Write(char value)
{
base.Write(value);
MethodInvoker action = delegate
{
myTextBox.AppendText(value.ToString());
};
myTextBox.BeginInvoke(action);
}
public override System.Text.Encoding Encoding
{
get { return System.Text.Encoding.UTF8; }
}
}
#----------------------------------------------------------
On May 27, 2016, at 5:40 PM, Saparya K <spryify at gmail.com> wrote:
> Just in case someone stumbles on this post looking for an answer:
>
> A solution that worked for me was redirecting the Python stdout/stderr to a stream in Python. I was then able to route this stream into the .NET text box.
>
> private void button1_Click(object sender, EventArgs e)
> {
> using
> (Py.GIL())
> {
> // Redirect stdout to text box
> dynamic sys = PythonEngine.ImportModule("sys");
>
> string codeToRedirectOutput =
> "import sys\n" +
> "from io import StringIO\n" +
> "sys.stdout = mystdout = StringIO()\n" +
> "sys.stdout.flush()\n" +
> "sys.stderr = mystderr = StringIO()\n" +
> "sys.stderr.flush()\n";
>
> PythonEngine.RunString(codeToRedirectOutput);
>
>
> // Run Python code
> string pyCode = "print(1 + 2)";
> PyObject result = PythonEngine.RunString(pyCode); // null in case of error
> if (result != null)
> {
> string pyStdout = sys.stdout.getvalue(); // Get stdout
> pyStdout
> = pyStdout.Replace("\n", "\r\n"); // To support newline for textbox
> textBox1
> .Text = pyStdout;
> }
> else
> {
> PythonEngine.PrintError(); // Make Python engine print errors
> string pyStderr = sys.stderr.getvalue(); // Get stderr
> pyStderr = pyStderr.Replace("\n", "\r\n"); // To support newline for textbox
>
> textBox1.Text = pyStderr;
> }
> }
> }
> With this code, I was able to redirect the stdout (and stderr in the case of an error) from the Python engine to a .NET text box.
>
>
> On Wed, May 18, 2016 at 12:02 AM, Saparya K <spryify at gmail.com> wrote:
> Hi Denis,
> Thanks for pointing me to the new API. I am now able to embed Python in my C# code and access Python classes and methods from C#!
>
> Hi Nils,
> Your application looks very interesting and some of the features (e.g. matplotlib integration) are on the lines of what I have been thinking about. I am far from there though and will need to learn more before I can follow all the code in your wrapper!
>
> -----
>
> As of now, I am trying to redirect the output from the Python interpreter to a .NET text box. While I am able to redirect the output to a file, I am having trouble with routing the output to a text box.
>
> I first tried to redirect the console output to a custom TextWriter using Console.SetOut in C#:
>
> private void Form1_Load(object sender, EventArgs e)
> {
> _writer = new TextBoxWriter(this.textBox1);
> Console.SetOut(_writer); // Redirect stdout to custom TextWriter that writes to the text box
> }
>
> This did not work: while output from C# is routed to the text box, output from Python is not.
>
> -----
>
> I then thought that maybe I need to redirect the Python stdout instead of the C# standard output. The idea was to assign Python's sys.stdout to a .NET object that implements the same interface as a python stream (write(), writelines()...):
>
> .NET class to mimic Python stream:
> • public class TextBoxStream : PyObject // To assign to sys.stdout. Is this correct?
> {
>
>
> private TextBox _output = null;
>
>
>
> public TextBoxStream() {}
>
>
>
> public TextBoxStream(TextBox output) {
>
> _output
> = output;
>
>
> }
>
>
>
> void write(object value) {
>
> _output
> .AppendText(value.ToString());
>
> }
>
> }
> In Form1.cs:
> private void button1_Click(object sender, EventArgs e) {
>
> using
> (Py.GIL())
>
>
> {
>
>
> // Redirect stdout to text box
>
>
> dynamic sys = PythonEngine.ImportModule("sys");
>
>
> TextBoxStream textBoxStream = new TextBoxStream(textBox1);
>
> sys
> .stdout = textBoxStream; // This is probably not theright way?
>
>
> //sys.SetAttr("stdout", textBoxStream); // This did not work either
>
>
>
> string code =
>
>
> "import sys\n" +
>
>
> "print 'Message 1'\n" +
>
>
> "sys.stdout.write('Message 2')\n" +
>
>
> "sys.stdout.flush()";
>
>
>
> PyObject redirectPyObj = PythonEngine.RunString(code); // returns NULL
>
> sys
> .stdout.write("Message 3");
>
>
> // Exception thrown: 'Python.Runtime.PyObject' does not contain a definition for 'stdout'
>
>
> }
> }
> This does not work either: redirectPyObj is NULL. I tried using the old as well as the new Python.NET API (with dynamic). Neither the sys.stdout.write nor the print statements write to the text box.
>
> Any ideas on how to approach this would be very helpful.
>
> Thanks,
> Saparya
>
>
> On Tue, May 17, 2016 at 3:33 AM, Nils Becker <nilsc.becker at gmail.com> wrote:
> Hey,
>
> a while ago I wrote something like a light wrapper around Python.NET to embed CPython with numpy/scipy in a .NET GUI. It manages local/global dictionaries, automatically converts simple data types and numpy arrrays<->C# arrays and provides a plotting widget in C# that shows matplotlib plots. It also has some other convenience functions.
>
> The code is by no means complete, fully tested or even nice. However, for me it works.
>
> I uploaded it to github: https://github.com/Lodomir/PythonInterface
> As it demonstrates some not-well documented use of Python.NET, I thought it maybe nice to share the code.
>
> You will need to add the references to Python.NET to build the main project (PythonInterface) and additionally to the PythonInterface-DLL to build the examples.
>
> Cheers
> Nils
>
> 2016-05-13 22:04 GMT+02:00 Denis Akhiyarov <denis.akhiyarov at gmail.com>:
> for embedding look at c# embedding unit tests and also here:
>
> 1. Old API:
>
> http://pythonnet.github.io/readme.html
>
> 2. New simplified API using dynamic:
>
> https://github.com/pythonnet/pythonnet/blob/master/README.md
>
>
>
> On Thu, May 12, 2016 at 4:16 PM, Saparya K <spryify at gmail.com> wrote:
> Thanks for your response, Denis.
>
> I had not come across Sho earlier. It looks very interesting. (If only Python 3.x support was available, though it does look like they have added support for their own math and visualization libraries).
>
> I am going over the demos and the unit tests and I was able to write a simple console application to access .NET objects from Python. This is very encouraging!
> I am still figuring out how to embed Python code in my C# WinForms application (instead of a console application).
>
> I will continue my experiments, but in the meantime if you or anyone else has any ideas on how to redirect the result from the Python interpreter (say, to a rich text box), I would love to hear them. That is one part of the puzzle that is unclear to me.
>
> Thanks,
> Saparya
>
> On Wed, May 11, 2016 at 4:01 PM, Denis Akhiyarov <denis.akhiyarov at gmail.com> wrote:
> This is definitely possible with WinForms or WPF. See the demo folder in pythonnet repo. One of the demo's is still in pull request.
>
> You should probably just try running previous IronPython attempts using pythonnet and report issues if any. Have a look at Sho from Microsoft.
>
> There is someone trying to embed ipython REPL using pythonnet/Excel-DNA or COM in Excel with Custom Task Pane (CTP) written in WinForms:
>
> https://groups.google.com/forum/#!topic/jupyter/CVht4orvQtc
>
>
>
>
>
> On Wed, May 11, 2016 at 4:44 PM, Saparya K <spryify at gmail.com> wrote:
> Hello PythonNet,
>
> I am looking to embed a Python interactive (REPL) shell in a .NET WinForms application.
> This C# application displays a graphical visualization of some data. Methods to manipulate the data in the C# application would be exposed via a Python API.
> The idea is to be able to interact with the data from the Python shell via the API, and thereby updating the graphical view.
>
> Ideally, the shell should support any valid Python syntax that is required to use the API. This would involve:
> • Querying a collection of data from the application via the Python API
> • Then manipulating this collection in the Python shell
> • Making API calls with the modified collection as an argument
> I came across a few examples where an interactive shell was developed using IronPython. A limitation with this approach is the absence of Python 3.x support (and other C-compiled libraries) in IronPython. For this reason, I would prefer to use Python.NET if it is possible.
>
> Has anyone here tried something like this with Python.NET before? Does it looks like what I am trying to achieve is feasible?
>
> Any direction would be very helpful!
>
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… Cameron
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