Execfile() - bug / strange behavior

[Gordon McMillan]

Amit Patel writes:

> I'm trying to understand why execfile(fn) is different from exec
> open(fn,'r').read().  Here's my program:
> 
> ====
> def timbot():
>     a = 3
>     execfile("1.txt")
>     print a
>     print locals()
> 
> timbot()
> ====
> 
> Then I have 1.txt:
> 
> ====
> a = 5
> b = 8
> ====
> 
> 
> When I run this, I expect to see a is 5, but I get:
> 
> ====
> 3
> {'b': 8, 'a': 3}
> ====
> 
> I don't understand why variable a is not set, but b is!  Even
> stranger, when I try to print b from timbot(), it gives me NameError,
> even though it's in locals()!

Perhaps this will give you a hint:
>>> execfile('1.txt')
>>> a
5
>>> b
8
>>>

 
> When I change execfile("1.txt") to exec open("1.txt",'r').read(), it
> works just fine!

That's because in the presence of an "exec" statement, locals 
don't get optimized to slots. As a function "execfile" gets no 
such special treatment. If you really want to use execfile, 
pass in the optional dicts and suck the values out of there.

not-a-bot-ly y'rs



- Gordon