Thanks for your great reply. I even augmented the reloading with the same dict
by clearing all of the non-standard symbols from the dict. This effectively
resets the dict:
# try to clear out the module by deleting all global refs
d = self.module.__dict__
for k in dict(d).keys():
if not k in ['__spec__', '__name__', '__loader__', '__package__',
'__doc__', '__builtins__']:
del d[k]
self.module.__dict__['sendMessage'] = self.sendMessage
try:
exec(self.source, self.module.__dict__)
except Exception:
import traceback
traceback.print_exc(file=sys.stdout)
Is there a better and more secure way to do the python-within-python in order
allow users to automate your app?
Thanks!
> On Nov 23, 2014, at 12:24 AM, Chris Angelico <[email protected]> wrote:
>
> On Sun, Nov 23, 2014 at 4:48 PM, Patrick Stinson <[email protected]>
> wrote:
>> I am writing a python app (using PyQt, but that’s not important here), and
>> want my users to be able to write their own scripts to automate the app’s
>> functioning using an engine API hat I expose. I have extensive experience
>> doing this in a C++ app with the CPython api, but have no idea how to do
>> this outside of calling exec() from with in Python :)
>>
>> Ideally their script would compile when the source changes and retain it’s
>> state and respond to callbacks from the api object. It appears this won’t
>> work with exec() because the script’s definitions and state disappear as
>> soon as the exec() call is complete, and the script doesn’t seem to be able
>> to access it’s own defined functions and classes.
>>
>> Thoughts? Fun stuff!
>
> First off, a cautionary note: Security-wise, this is absolutely
> equivalent to your users editing your source code. Be aware that
> you're giving them complete control.
>
> What you should be able to do is exec the script in a specific global
> dictionary. Here's some example code (Python 3.4):
>
>>>> script = """
> def init():
> print("Initializing")
>
> def on_some_event(status):
> trigger_some_action("Status is now "+status)
> """
>>>> def trigger_some_action(msg):
> print("Action triggered.",msg)
>>>> globl = {"trigger_some_action":trigger_some_action}
>>>> exec(script,globl)
>>>> globl["init"]()
> Initializing
>>>> globl["on_some_event"]("Something happened")
> Action triggered. Status is now Something happened
>
> You can provide globals like this, or you can create an importable
> module for the scripts to call on. (Or both. Create a module, and
> pre-import it automatically.) The script defines functions with
> specific names and/or calls your functions to register hooks; you can
> reach into the globals to trigger functions.
>
> One way to handle updates to the code would be to exec it in the same
> globals dictionary. That has its complexities (for instance, if you
> rename a function, the old version will still exist under the old name
> unless you explicitly del it), but it can be very convenient.
> Alternatively, you could have the new version run in a new dictionary,
> but important state can be kept in separate dictionaries. That's how I
> manage things with a Pike program - all code gets reloaded cleanly,
> but retained state is stored separately in a mutable object that gets
> passed around.
>
> There are several ways this sort of thing can be done. It's reasonably
> easy, as long as you take a bit of care across the reload boundaries.
>
> ChrisA
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