__init__.py, __path__ and packaging

[Sandro Dentella]

In comp.lang.python, hai scritto:
> Sandro Dentella wrote:
>> The structure of my package:
>> 
>> python/
>> `-- dbg/
>>    |-- __init__.py
>>    `-- lib
>>        |-- __init__.py
>>        |-- debug.py
>>        `-- gtk_dbg.py
>> 
>> my sys.path includes 'python' and I wanted that the content of debug.py was
>> simply included by: 'import dbg', so I wrote dbg/__init__.py as follows:
>> 
>>     import os
>>     Dir = os.path.dirname(__file__)
>>     __path__ = [os.path.join(Dir, 'lib')]
>>     from debug import *
>
> What you probably want in python/dbg/__init__.py to get values is:
>
>      from dbg.lib.debug import *

This does not work:

   Traceback (most recent call last):
     File "<string>", line 1, in ?
     File "dbg/__init__.py", line 8, in ?
       from dbg.lib.debug import *
   ImportError: No module named lib.debug



>
>> BUT, if I set some variables they are not correctly seen:
>>     import dbg
>>     dbg.DBG = 1
>> function test included in debug.py raises NameError:
>>     def test():
>>         print DBG
>> NameError: global name 'DBG' is not defined`
>> 
>> What's happening? DBG seems to be set, as shown by dir(dbg)... any hints?
> You misunderstand modules and python variables.  Each module has a
> dictionary associating the names of its globals and their current
> values.  After:
>      import dbg.lib.debug, dbg.lib.gtk_dbg
> you have four modules:
>      dbg             # Corresponds to python/dbg/__init__.py
>      dbg.lib         # Corresponds to python/dbg/lib/__init__.py
>      dbg.lib.debug   # Corresponds to python/dbg/lib/debug.py
>      dbg.lib.gtk_dbg # Corresponds to python/dbg/lib/gtk_dbg.py
> Each has its own globals.
> after:
>      dbg.DBG = 1
> the dbg module's global dictionary contains an entry mapping 'DBG' to 1
> after:
>      dbg.DBG = 1+2
> the dbg module's global dictionary contains an entry mapping 'DBG' to 3
>
> In no case will an assignment to a global in dbg cause an assignment to
> anything in dbg.lib.debug.  The "from dbg.lib.debug import *" statement
> can be seen as a module import followed by a fancy multiple assignment,
> where module dbg.lib.debug is first imported, then its globals are
> assigned to globals of the same names in module dbg.

This confirms to me that I'm seriously confused... so I started with a very
simple setup:
$ cat dbg.py
DBG = 1
def test():
    global DBG
    print DBG

def set():
    global DBG
    DBG = 3


$ cat m.py
from  dbg import *

test()
#dbg.DBG = 2   ## does not work, no way to assign in module dbg
set()          # this acts in dbg module and sets 'DBG = 3'
test()         # test the value of DBG
print DBG


$ python m.py
1
3  # changed by 'set' that was 'imported'
1  # value of local DBG

isn't this contraddicting you words:

> can be seen as a module import followed by a fancy multiple assignment,
> where module dbg.lib.debug is first imported, then its globals are
> assigned to globals of the same names in module dbg.

So: which is the way I can change a value of a package 'imported', only with
a function that sets it? is there a way to assign the value directly?
is there any way to make some introspection of what is really there (in
dbg)?

Thanks angain for any possible hint.

sandro
*:-)



-- 
Sandro Dentella  *:-)
http://www.tksql.org                    TkSQL Home page - My GPL work