[Edu-sig] How to pass parameters to eval?

[Mats Wichmann]

At 12:30 PM 9/26/2001 -0700, you wrote:
 >Hi,
 >   I appreciate all replies to my previous quesions.
 >This time,  I am trying to pass two parameter to eval
 >function so it can evaluate and return the result base
 >on the parameter i gave. For examples:
 >
 >********func.py***************
 >def fun ():
 >   print v1+v2
 >
 >**************pro.py***********
 >from func import *
 >funname = "fun()"
 >v1 = "Hello "
 >v2 = "World"
 >eval(funname)
 >****************************
 >I know these code will not run. If i put fun in the
 >same file as pro.py, it works. What i want is to let
 >fun in func.py to have access to variable v1 and v2
 >which are declared in pro.py. How can i do this? Any
 >guidance or suggestion is highly appreciated.

I guess the question that comes up is why? This
seems a pretty convoluted construct.

 From the point of view of module func, v1 and
v2 are undefined; they're only visible in the
namespace of the main program.  You can make this
work by having func.py import v1 and v2 from pro
(and moving the eval to protected code:
if __name__ == '__main__').

Normally you can pass eval() the namespaces
it's going to operate in, but since what eval
here does is run a function in a different
module, you change context when the function
runs.

If you truly want program-global symbols,
it seems better to put them in a separate file
and have everybody import that.

But most folks seem to think if you find a need
to do that the design of the program could use
some rethinking....