execfile then import back

[overly.crazy.steve]

I am seeing something strange with execfile. I've simplified the code
to:

########## t.py ##########
print "here"
v = None

def f():
global v
v = 6

if __name__ == "__main__":
f()
print "0:", v
execfile("x.py" )
print "0:", v
execfile("y.py" )
print "0:", v

########## x.py and y.py (they are identical) ##########
import testexec
print "1:", v, testexec.v
testexec.v = 7

Runing "python t.py" (with Python 2.4.2), the printout I got is:

here
0: 6
here
1: 6 None
0: 6
1: 6 7
0: 6

So there is apparently 2 different instances of v at run time. Can
someone please explain (1) why this is the case, and (2) assuming this
is correct behavior, how I can avoid this? Thanks.

[overly.crazy.steve]

> ########## x.py and y.py (they are identical) ##########

import testexec
print "1:", v, testexec.v
testexec.v = 7

Oops, testexec should be changed to t instead. That is:

########## x.py and y.py (they are identical) ##########
import t
print "1:", v, t.v
t.v = 7

[overly.crazy.steve]

Dennis Lee Bieber wrote:

And the problem you are seeing is that the initial "v" in the t.py
that you "run", is considered "__main__.v ", NOT "t.v"

Yes, the 2 different copies of v apparently imply that __main__ and t
are 2 different modules. But I had expected __main__ to be an alias of
t. Can you point out the passage in Python doc that explains this?