Embedding a Python shell inside a Python program

Question

I am making a sort of a science lab in Python, in which the user can create, modify and analyze all sorts of objects. I would like to put a Python shell inside the program, so the user could manipulate the objects through the shell. (Note: He could also manipulate the objects through the usual GUI.)

A mockup that illustrates this: http://cool-rr.com/physicsthing/physicsthing_mockup_thumb.gif

How can I make this sort of thing?

I considered using eval, but I understood that eval can't handle import, for example.

Answer 1

You are looking for code - Interpreter base classes, particularly code.interact().

Some examples from effbot.

• Van Gale: Well, the link to docs is 2.6 and all you need to do is call code.interact(). For another example, here's a link to the Django shell command that is both current and also works with IronPython: code.djangoproject.com/browser/django/trunk/django/core/…
• Van Gale: ..that's just for reference for other people needing to embed interpreter. If you're using wxPython then PyCrust is definitely a better solution.

Answer 2

Depending on your GUI framework, it may already has been done:

• For wxpython, look up "PyCrust" - it's very easy to embed into your app
• For PyQt, pyqtshell (Update 29.04.2011: these days called spyder)

Here's what I did to embed PyCrust into the application:

import wx.py.crust
...
...
# then call
crustFrame = wx.py.crust.CrustFrame(parent = self)
crustFrame.Show()

The self here refers to my main frame (derived from wx.Frame). This creates a PyCrust window that runs in your application and allows you to inspect everything stored in your main frame (because of the self).

• Ram Rachum: I looked up PyCrust, but I don't understand- Does it create another instance of Python? I need something that will control the same instance of Python that the main program runs in.
• Eli Bendersky: Added code sample. It runs in the same instance, and can access (and modify) the the object that is given it as a parent.
• 9b5b: pyqtshell was renamed to pydee was renamed to spyder

Answer 3

FWIW, I believe Enthought has written something like this for use with their Python-based (and NumPy-based) visualization suite. I saw a demo two years ago where they indeed let you manipulate objects directly via the GUI or via the Python interpreter.

Also, to add to the first answer, you might have to subclass code.InteractiveConsole to override self.read() and self.write(), so they interact with the GUI. And you'll also have to redirect sys.stdout and sys.stderr to some writable class that writes to the same console.

• Ram Rachum: Before I begin digesting your answer- Do you happen, by any chance, to be Guido?

Answer 4

The Python eval() function only handles expressions. You may want to consider the exec statement instead, which can run any arbitrary Python code.

Answer 5

I use pdb.set_trace() as a shell. It also has some debugging capabilities :)