Problem with exec

[Larry Bates]

Antoon Pardon wrote:
> I have the following little piece of code:
> 
> class Cfg:pass
> #config = Cfg()
> 
> def assign():
>   setattr(config, 'Start' , [13, 26, 29, 34])
> 
> def foo():
>   config = Cfg()
>   dct = {'config':config, 'assign':assign}
>   exec "assign()" in dct
>   print config.Start
> 
> foo()
> 
> 
> When I execute this I get the following error:
> 
> Traceback (most recent call last):
>   File "mod1.py", line 13, in ?
>     foo()
>   File "mod1.py", line 10, in foo
>     exec "assign()" in dct
>   File "<string>", line 1, in ?
>   File "mod1.py", line 5, in assign
>     setattr(config, 'Start' , [13, 26, 29, 34])
> NameError: global name 'config' is not defined
> 
> Now I don't understand this. In the documentation I read the following:
> 
>   If only the first expression after in is specified, it should be a
>   dictionary, which will be used for both the global and the local
>   variables.
> 
> I provided a dictionary to be used for the global variables and it
> contains a 'config' entry, so why doesn't this work?
> 

Not entirely sure why you want to do what you have outlined
here but this works:

class Cfg:
    pass
#config = Cfg()

def assign(config):
    setattr(config, 'Start' , [13, 26, 29, 34])

def foo():
    config = Cfg()
    assign(config)
    print config.Start

foo()

You should probably post what you are trying to do.  Maybe we
can make a suggestion about the best approach.

-Larry Bates