Printing a variable in an embedded Python interpre

I have written a small C program that embeds Python. I'm setting it up correctly using Py_Initialize() and Py_Finalize(), and am able to run scripts either using PyRun_SimpleString or PyRun_SimpleFile. However, I don't know how mimic the behavior of Python's own interpreter when printing variables.

Specifically:

a = (1, 2, 3)
print a

Works fine for me: it prints out (1, 2, 3)

However:

a = (1, 2, 3)
a

Prints out nothing at all. In Python's own interpreter, this would print out (1, 2, 3) as well. How can I make my code do what users would expect and print out the value?

Thanks in advance!

To run the interpreters interactive loop, you should use the function PyRun_InteractiveLoop(). Otherwise, your code will behave as if it were written in a Python script file, not entered interactively.

Edit: Here's the full code of a simple interactive interpreter:

#include <Python.h>

int main()
{
    Py_Initialize();
    PyRun_InteractiveLoop(stdin, "<stdin>");
    Py_Finalize();
}

Edit2: Implementing a full interactive interpreter in a GUI is a bit of a project. Probably the easiest way to get it right is to write a basic terminal emulator connected to a pseudo-terminal device, and use the above code on that device. This will automatically get all subtleties right.

If your aim isn't a full-blown interactive editor, an option might be to use PyRun_String() with Py_single_input as start token. This will allow you to run some Python code as in the interactive interpreter, and if that code happened to be a single expression that doesn't evaluate to None, a representation of its value is printed -- to stdout of course. Here is some example code (without error checking for simplicity):

#include <Python.h>

int main()
{
    PyObject *main, *d;
    Py_Initialize();
    main = PyImport_AddModule("__main__");
    d = PyModule_GetDict(main);
    PyRun_String("a = (1, 2, 3)", Py_single_input, d, d);
    PyRun_String("a", Py_single_input, d, d);
    Py_Finalize();
}

This will print (1, 2, 3).

There are still a lot of problems:

No error handling and traceback printing.
No "incremental input" for block commands like in the interactive interpreter. The input needs to be complete.
Output to stdout.
If multiple lines of input are given, nothing is printed.

To really replicate the behaviour of the interactive interpreter is not easy. That's why my initial recommendation was to write a basic terminal emulator in your GUI, which shouldn't be too hard -- or maybe there's even one available.