Variable scope and caller

[Ben Leslie]

On Sun, 15 Dec 2002, Erik Lechak wrote:

> Hello all,
> 
> 
> This is what it would look like when it works:
> 
>    a = pstring("hello $b")
>    b = "erik"
>    print a
>    b = "moon"
>    print a
> 
> OUTPUT
> hello erik
> hello moon
> 
> 
> In other words the __str__ function will find the local variables (and
> globals) then do a replace on the elements of the string starting with
> '$'.  This is one of the main features of perl and I would like to
> prove it to myself that python can handle it without resorting to all
> kinds of trickery.

Well, you need a little bit of trickery.
 
> In the bit of code below, what scope is 'a=locals()' in.  I thought it
> would be in the calling functions scope.  But it does not appear to
> be.
> 
> I have also tried 'a=globals()' and 'a=vars()'.
> 
> class pstring:
>    data = ""
>    def __init__(self, st = ""):
>       self.data = st      
>    def __str__(self , a=locals()):
>       print a
>       return self.data
> 
> def testit():
>    y = "erik"
>    x = pstring("hello $y")
>    print x
> 
> testit()


"""
import inspect
class pstring:
   data = ""
   def __init__(self, st = ""):
	   self.data = st
   def __str__(self):
	   a = inspect.currentframe().f_back.f_locals
	   print a
	   print a['y']
	   return self.data

def testit():
	y = "erik"
	x = pstring("hello $y")
	print locals()
	print x

testit()
"""

Benno