break in a module

Thu Jun 16 22:11:29 EDT 2011

Erik Max Francis wrote:
> Chris Angelico wrote:
>> On Fri, Jun 17, 2011 at 10:48 AM, Steven D'Aprano
>> <steve+comp.lang.python at pearwood.info> wrote:
>>> Perhaps the most sensible alternative is conditional importing:
>>>>>> # === module extras.py ===
>>>>>> def ham(): pass
>>> def cheese(): pass
>>> def salad(): pass
>>>>>>>>> # === module other.py ===
>>>>>> def spam(): pass
>>>>>> if not some_condition: from extras import *
>>>>>>> This would, if I understand imports correctly, have ham() operate in
>> one namespace and spam() in another. Depending on what's being done,
>> that could be quite harmless, or it could be annoying (no sharing
>> module-level constants, etc).
>> No, he's using `from ... import *`. It dumps it all in the same 
> namespace 

Wrong, with a little bit right. The 'from ... *' functions are now 
bound in the calling namespace, but they still execute in their original 
namespace. Observe:
8<--these.py---------------------------------------------------------
import this
this.yummy()
8<--this.py----------------------------------------------------------
breakfast = 'ham and eggs'
def spam():
 print(breakfast)
if 'spam' not in breakfast:
 from that import *
8<--that.py----------------------------------------------------------
def yummy():
 print(breakfast)
8<--results----------------------------------------------------------
--> import these
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "these.py", line 3, in <module>
 this.yummy()
 File "that.py", line 2, in yummy
 print(breakfast)
NameError: global name 'breakfast' is not defined
8<-------------------------------------------------------------------
~Ethan~