Steven D'Aprano <[EMAIL PROTECTED]> wrote:
> On Tue, 02 Dec 2008 11:12:31 +0000, Nick Craig-Wood wrote:
>
> > I prefer the "from module import function". That means that if "module"
> > doesn't supply "function" it raises an exception at compile time, not
> > run time when you try to run "module.function".
>
> Wanna bet?
>
>
> >>> def spam():
> ... from math import harmonic_series
> ... return harmonic_series()
> ...
> >>> dis.dis(spam)
> 2 0 LOAD_CONST 1 (-1)
> 3 LOAD_CONST 2 (('harmonic_series',))
> 6 IMPORT_NAME 0 (math)
> 9 IMPORT_FROM 1 (harmonic_series)
> 12 STORE_FAST 0 (harmonic_series)
> 15 POP_TOP
>
> 3 16 LOAD_FAST 0 (harmonic_series)
> 19 CALL_FUNCTION 0
> 22 RETURN_VALUE
> >>> spam()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> File "<stdin>", line 2, in spam
> ImportError: cannot import name harmonic_series
>
>
> The same thing happens if the from...import is at the top level of the
> module, except that compilation is immediately followed by
> execution.
You are technically right I am sure.
However the error happens when you import the module with the error
in, not when you run stuff from it which is the major difference.
$ echo -e "from os import sausage\n" > import_test.py
$ python
Python 2.5.2 (r252:60911, Sep 29 2008, 21:15:13)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> # This does produce an error
>>> import import_test
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "import_test.py", line 1, in <module>
from os import sausage
ImportError: cannot import name sausage
>>>
$ # This produces an error also
$ python import_test.py
Traceback (most recent call last):
File "import_test.py", line 1, in <module>
from os import sausage
ImportError: cannot import name sausage
$
Unlike
$ echo -e "import os\ndef f(): os.sausage\n" > import_test.py
$ python
Python 2.5.2 (r252:60911, Sep 29 2008, 21:15:13)
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> # This doesn't produce an error
>>> import import_test
>>> # Until you actually call it
>>> import_test.f()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "import_test.py", line 2, in f
def f(): os.sausage
AttributeError: 'module' object has no attribute 'sausage'
>>>
$ # No error here either
$ python import_test.py
$
> > It then becomes very easy to see which functions you use from any
> > given module too.
>
> If that's important to you. Personally, I find it more useful to know
> where a function is defined.
We can agree to differ there I'm sure ;-)
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
--
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