Exec and Scope

[Emanuele D'Arrigo]

Hi everybody!

I'm trying to do something in a way that is probably not particularly
wise but at this point I don't know any better, so bear with me.

Suppose in main.py I have the following statements:

myObject = MyObject()
execThis("myObj ect.myCommand() ")

Now suppose the method

def execThis(aComma ndInAString):
exec(aCommandIn AString)

is somewhere "far away" in terms of scope. Somewhere where the code
doesn't know anything about the instance myObject and even less about
its methods and attributes. How do I get myObject.myComm and() properly
executed?

I'm guessing it's about taking a snapshot of or a reference to the
namespace that is correct for the execution of the command, but... is
that the case? And how do I get a handle to that?

Thanks for your help!

Manu

[James Mills]

Re: Exec and Scope

Manu,

Good lord man, what are you trying to solve ?
Describe your "actual problem" you're attempting
to solve... This looks really really ugly and I would
advise against any solution that relies on exec()

--JamesMills

On Fri, Oct 31, 2008 at 1:47 PM, Emanuele D'Arrigo <manu3d@gmail.c omwrote:

Hi everybody!
>
I'm trying to do something in a way that is probably not particularly
wise but at this point I don't know any better, so bear with me.
>
Suppose in main.py I have the following statements:
>
myObject = MyObject()
execThis("myObj ect.myCommand() ")
>
Now suppose the method
>
def execThis(aComma ndInAString):
exec(aCommandIn AString)
>
is somewhere "far away" in terms of scope. Somewhere where the code
doesn't know anything about the instance myObject and even less about
its methods and attributes. How do I get myObject.myComm and() properly
executed?
>
I'm guessing it's about taking a snapshot of or a reference to the
namespace that is correct for the execution of the command, but... is
that the case? And how do I get a handle to that?
>
Thanks for your help!
>
Manu
--

http://mail.python.org/mailman/listinfo/python-list

>

--
--
-- "Problems are solved by method"

[Rafe]

Re: Exec and Scope

On Oct 31, 10:47 am, "Emanuele D'Arrigo" <man...@gmail.c omwrote:

Hi everybody!
>
I'm trying to do something in a way that is probably not particularly
wise but at this point I don't know any better, so bear with me.
>
Suppose in main.py I have the following statements:
>
myObject = MyObject()
execThis("myObj ect.myCommand() ")
>
Now suppose the method
>
def execThis(aComma ndInAString):
    exec(aCommandIn AString)
>
is somewhere "far away" in terms of scope. Somewhere where the code
doesn't know anything about the instance myObject and even less about
its methods and attributes. How do I get myObject.myComm and() properly
executed?
>
I'm guessing it's about taking a snapshot of or a reference to the
namespace that is correct for the execution of the command, but... is
that the case? And how do I get a handle to that?
>
Thanks for your help!
>
Manu

If you are just looking to execute an attribute (be it a property,
module-level function, instance or class method, or anything else
which is an attribute of an object), just use getattr().

Execute a 'method' (which is just a callable object right?) of an
instance of MyObject named "myCommand" :

>>class MyObject(object ):

.... def my_command(self ):
.... print "hello"
....

>>myObject = MyObject()
>>attr = getattr(myObjec t, "my_command ")
>>attr()

hello


- Rafe

[Emanuele D'Arrigo]

Re: Exec and Scope

On Oct 31, 4:38 am, Rafe <rafesa...@gmai l.comwrote:

If you are just looking to execute an attribute (be it a property,
module-level function, instance or class method, or anything else
which is an attribute of an object), just use getattr().

I must check this out. My understanding is that getAttr returns a
function object that happens to be a method of that object. I can then
invoke that function as if I was invoking the method of that object.
What I don't know is: will the function work in a scope where the
object is not defined? And even if it does, what happens to the names
that refer to the containeR or containeD objects?

I've read what I could in the manual about the data model, scope and
namespaces but as you can probably see there still are things I do not
fully comprehend. I feel a bit like seeing the dots but not quite
being able to make the connections between them just yet.

Thanks for your help though! This is providing me with a few ideas for
some more tests to do.

Manu

[Emanuele D'Arrigo]

Re: Exec and Scope

Ahh... before you guys reply: I found the way.

Between you James sounding the horn of alarm and you Rafe pointing me
in the right direction I sorted it out. Eventually I didn't end up
using getAttr but looking into it I learned the difference between

myResult = instance.method ()

and

myMethod = instance.method

the latter can be passed as an object for execution inside a function,
i.e.:

def myCommand(input Method):
inputMethod()

myCommand(myMet hod)

and that works flawlessly! Thank you guys!

Manu