Re: [Jython-dev] Assigning to func_code (proof of concept)

[Paul D. F. <pdf...@ku...>]

Just to wrap this up... (even though it is moving off-topic for 
Jython-dev, but I can add I am impressed I could do it without code 
changes to Jython. :-)

Here is a proof of concept of dynamic code changes while running, based on 
Kent's suggestion.

I and others have done this before even with fancier module reloading and 
assigning existing instances to a reloaded (so, new) class instance, to 
get the old instances to use the new class, to get around:
   http://docs.python.org/lib/built-in-funcs.html
   "If a module instantiates instances of a class, reloading the module 
that defines the class does not affect the method definitions of the 
instances -- they continue to use the old class definition. The same is 
true for derived classes."
but I've never quite seen it this way -- where a previously assigned GUI 
callback works with the new change, because those references are 
squirreled away outside the easy reach of module reloaders, and so the GUI 
continues to callback into the old code (even with the instance 
referencing the newer reloaded class). Doesn't mean it hasn't been done 
though, if anyone knows of examples, please let me know.

The test consists of two files -- run test.py, it launches two windows, 
one that can do reloading, one that prints "hello world". Modify the code 
of the second window in the OnHello method and do a reload. The new 
OnHello method will be called by the old window when the "hello" button is 
pressed. You can uncomment the other line, or make your own changes.

It's still a little klunky -- it was not obvious to me how to reload a 
changed module into a new object without brute force removing the old one 
from sys.modules and then putting it back afterwards.

Except for the obvious Swing dependency, I don't see why this would not 
work under CPython and one of those GUI toolkits (wx, tk, etc.)

====== test.py =============

from javax.swing import JFrame, JButton
from java.awt import FlowLayout

import sys

from hello import HelloFrame

class ReloaderFrame(JFrame):
     def __init__(self):
         self.contentPane.layout = FlowLayout()
         button = JButton("Reload", actionPerformed=self.OnReload)
         self.contentPane.add(button)
         self.setBounds(50, 100, 100, 100)
         self.pack()
         self.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

     def OnReload(self, event):
         print "reload"
         helloModule = sys.modules["hello"]
         print helloModule
         print dir(helloModule)
         print helloModule.HelloFrame
         print helloModule.HelloFrame.OnHello
         print helloModule.HelloFrame.OnHello.im_func
         print helloModule.HelloFrame.OnHello.im_func.func_code
         # temporarily remove old module and later restore it
         del sys.modules["hello"]
         newHelloModule = __import__("hello")
         sys.modules["hello"] = helloModule
         print newHelloModule
         print "helloModule == newHelloModule", helloModule == newHelloModule
         newFunctionCode = newHelloModule.HelloFrame.OnHello.im_func.func_code
         print newFunctionCode
         helloModule.HelloFrame.OnHello.im_func.func_code = newFunctionCode

window = ReloaderFrame()
window.visible = 1

window = HelloFrame()
window.visible = 1

======================= hello.py ======================

from javax.swing import JFrame, JButton
from java.awt import FlowLayout

class HelloFrame(JFrame):
     def __init__(self):
         self.contentPane.layout = FlowLayout()
         button = JButton("Hello", actionPerformed=self.OnHello)
         self.contentPane.add(button)
         self.setBounds(200, 100, 100, 100)
         self.pack()
         self.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

     def OnHello(self, event):
         print "hello world"
         #print "made a change"

=========================================================

TO DO: handle updating all the methods in a class, more bells and 
whistles, changing the code inside the debugger or a popup traceback 
window, etc..

Don't understand why this has not been done before -- still waiting for 
the hidden gotchas (beyond obvious module reloading side effects). :-)

--Paul Fernhout

Paul D. Fernhout wrote:
> Thanks again. Now onto a proof of concept towards reloading a Swing GUI 
> class from a module but modifying what methods of existing graphical 
> objects do.