En Wed, 12 Mar 2008 18:02:54 -0200, Jean-Paul Calderone
<[EMAIL PROTECTED]> escribió:
> On Wed, 12 Mar 2008 12:58:33 -0700 (PDT), George Sakkis
> <[EMAIL PROTECTED]> wrote:
>> On Mar 12, 12:22 pm, mrstephengross <[EMAIL PROTECTED]> wrote:
>>
>>> Hi all. I've got a python file called 'foo' (no extension). I want to
>>> be able to load it as a module, like so:
>>>
>>> m = __import__('foo')
>>>
>> You can use execfile:
>>
>> foo = {}
>> execfile('foo', foo)
>>
>> Apart from the different syntax in accessing the module globals
>> (attributes with __import__ (foo.x) vs dict entries with execfile
>> (foo['x'])), there are probably more subtle differences but I can't
>> tell for sure. It would be nice if someone more knowledgeable can
>> compare and contrast these two appraches.
>
> Another difference is that when you import a module, its code is
> (usually)
> only executed once. Each import after the first just returns a reference
> to the already-created module object. When you use execfile, the code is
> re-evaluated each time.
The steps done by import are outlined in this message
http://groups.google.com/group/comp.lang.python/browse_thread/thread/7d0ef70c1adc39ac/3882ce35f13ff971#msg_96a590bca5f2be8c
The relevant part (citing myself):
newmodule = sys.modules[modulename] = ModuleType(modulename)
# constructor sets __name__ and a null __doc__
newmodule.__builtins__ = current builtins
newmodule.__file__ = filename
code = read from filename and compile it
exec code in newmodule.__dict__
Apart from sys.modules and __file__, there is another difference, the
__builtins__ attribute. It is important: if not present, Python executes
the code in "safe mode" where certain operations are disabled (and there
is a big performance penalty).
--
Gabriel Genellina
--
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