Import problem

[Steve Holden]

Achim Domma (Procoders) wrote:

> Achim Domma (Procoders) wrote:
> 
>> Seems like I'm mixing up something in a very bad way, but I have no 
>> idea what I'm doing wrong!?
> 
> 
> I have moved the calculation of VERSION to a module _Version.py which 
> contains a function Version(), which is imported by __init__.py and 
> _C.py. That works and is much cleaner, but I would still be happy if 
> somebody could explain we, what's going wrong.
> 
> regards,
> Achim

Well, the big problem with your original formulation is your circular 
imports. In brief ...

If A imports B, and B imports A, the copy of A that B sees is the 
incompletely-executed definition at the time that the import of B was 
started.

When you say in your first post """
Now I should be able to write:

import A.B
if A.B.VERSION[0]=5:
     do_something()

but

from A.B import VERSION

does not work.""", are you trying to use both those formulations in the 
same module? You do not explain what you mean by "does not work", so I 
suspect that you are trying to use a package=based reference 
(A.B.VERSION) when you have actually imported the VERSION variable into 
your namespace.

sholden at dellboy ~
$ cat pkg/__init__.py
#!/usr/bin/python
objv = "2.3.45"
VERSION = tuple([int(x) for x in objv.split(".")])
del objv

sholden at dellboy ~
$ python -c "from pkg import VERSION; print VERSION"
(2, 3, 45)

The above is not an exact match for your code, but it shows that when 
you use the "from" form of the import statement the imported variables 
appear directly in the namespace of the importing module, so there is no 
need to qualify them with the package name.

Hope this helps. If not, perhaps you could post some actual error 
messages to explain what you mean by "does not work".

regards
  Steve
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