__init__.py, __path__ and packaging

[Sandro Dentella]

Hi everybody,

I'm trying to fix the packaging of a very simple package, but some problem
show me that I have not well understood the whole mechanism

The structure of my package (some debug functions) is as follows:

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(Di r, 'lib')]
from debug import *

It seems to work:

python$ python -c 'import dbg; print dir(dbg)'
['DBG', 'Dir', '__builtins__', '__doc__', '__file__', '__name__', \
'__path__', 'caller', 'debug', 'dshow', 'os', 're', 'show_caller', \
'sql_debug', 'sys']

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?
I'd also accept a hint for a different approch, if it's the case, but I'd
really would also understant this issue

Thanks in advance
sandro
*:-)

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

[Scott David Daniels]

Re: __init__.py, __path__ and packaging

Sandro Dentella wrote:[color=blue]
> 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(Di r, 'lib')]
> from debug import *[/color]

What you probably want in python/dbg/__init__.py to get values is:

from dbg.lib.debug import *
[color=blue]
> 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?[/color]
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.

--Scott David Daniels
scott.daniels@a cm.org

[Sandro Dentella]

Re: __init__.py, __path__ and packaging

In comp.lang.pytho n, hai scritto:[color=blue]
> Sandro Dentella wrote:[color=green]
>> 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(Di r, 'lib')]
>> from debug import *[/color]
>
> What you probably want in python/dbg/__init__.py to get values is:
>
> from dbg.lib.debug import *[/color]

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


[color=blue]
>[color=green]
>> 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?[/color]
> 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.[/color]

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:
[color=blue]
> 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.[/color]

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

[Sandro Dentella]

Re: __init__.py, __path__ and packaging

> Now, why you couldn't do "dbg.DBG = ..."? Very simple... "from[color=blue]
> module import *" doesn't give you a dbg /module/, it only gives you
> references to each piece inside the module.[/color]

really the reason why I wanted that should probably be solved in other
ways. I just wanted to split my dbg module in different files but load the
dbg module in one single operation:

dbg/
|-- __init__.py
|-- lib
|-- __init__.py
|-- debug.py
|-- gtk_dbg.py

and inside dbg/__init__.py I used "from dbg.debug import *" so that a single
'import dbg' could present me the module 'debug' (of course in this simple
case seems easier to put debug.py directly under dbg, but my main case is
a much more complex module, with a tree structure that reflects the
relation between modules that I want to hide to the end user).

But to summarize, if I use 'from my_module import *' there is no way to reach
directly 'my_module' and set a variable there?

Thanks again
sandro
*:-)
[color=blue]
> I'm trying to fix the packaging of a very simple package, but some problem
> show me that I have not well understood
>
> the structure of my package (some debug functions) is as follows:
>
> 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(Di r, 'lib')]
> from debug import *
>
>[/color]
--
Sandro Dentella *:-)
e-mail: sandro@e-den.it
http://www.tksql.org TkSQL Home page - My GPL work