global name space and importing

Moshe Zadka moshez at math.huji.ac.il
Sun May 28 07:08:50 CEST 2000


On Sat, 27 May 2000, Curtis Jensen wrote:

> How come the global declaration works when I define it from withing the
> interpreter, but not from within a file that I import?  See following
> example.
> 
> file: foo_bar.py:
> def foo(i):
>   x = i
> 
> def bar(i):
>   global y
>   y = i
> 
> Python interpreter:
> >>> from foo_bar import *

Yet another example on why "from foo import *" is evil.
It imports all the names *currently* in the module. "y" is not in the
module until you *call* bar.

>>> from foo import *
>>> bar()
>>> from foo import *
>>> y
1

Where 

# foo.py
def bar():
	global y
	y = 2

Solution: don't do 'from ... import *'

--
Moshe Zadka <moshez at math.huji.ac.il>
http://www.oreilly.com/news/prescod_0300.html
http://www.linux.org.il -- we put the penguin in .com





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