Packaging question
Peter Otten
__peter__ at web.de
Fri Jul 2 04:22:31 EDT 2010
snorble wrote:
> My question is, why do the modules bar and foo show up in mypack's
> dir()? I intend for Foo (the class foo.Foo) and Bar (the class
> bar.Bar) to be there, but was not sure about the modules foo and bar.
> $ ls mypack/*.py
> bar.py
> foo.py
> __init__.py
>
> $ cat mypack/__init__.py
> from foo import Foo
> from bar import Bar
>
> $ python
> Python 2.6.5 (r265:79096, Mar 19 2010, 21:48:26) [MSC v.1500 32 bit
> (Intel)] on win32
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import mypack
>>>> dir(mypack)
> ['Bar', 'Foo', '__builtins__', '__doc__', '__file__', '__name__',
> '__package__', '__path__', 'bar', 'foo']
How is Python to know that you won't perform an
import mypack.foo
afterwards? After this statement foo must be an attribute of mypack. But
when mypack.foo has been imported before this just performs
mypack = sys.modules["mypack"]
If the foo attribute weren't added by
from foo import Foo
the caching mechanism would not work. While
import mypack.foo
might also have been implemented as
mypack = sys.modules["mypack"]
if not hasattr(mypack", "foo"):
mypack.foo = sys.modules["mypack.foo"]
I think that would have been a solution to a non-problem. If you're sure you
don't need to access mypack.foo directly you can add
del foo
to mypack/__init__.py, but don't complain when you get bitten by
>>> import mypack.foo
>>> mypack.foo
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'foo'
> My big picture intention is to create smaller modules, but more of
> them (like I am used to doing with C++), and then use a package to
> organize the namespace so I'm not typing out excessively long names
> and making the code less readable. Is that a reasonable approach to
> developing Python programs?
I like to put related classes and functions into a single file. As a rule of
thumb, when a class needs a file of its own the class is too big...
Peter
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