redundant imports

[max(01)*]

Mike Meyer wrote:
> "max(01)*" <max2 at fisso.casa> writes:
> 
> 
>>Peter Hansen wrote:
>>
>>>max(01)* wrote:
>>>
>>>
>>>>hi everybody.
>>>>
>>>>suppose that code-1.py imports code-2.py and code-3.py (because it
>>>>uses names from both), and that code-2.py imports code-3.py.
>>>>
>>>>if python were c, code-1.c should only *include* code-2.c, because
>>>>the latter in turns includes code-3.c.
>>>>
>>>>inclusion of modules in c is a purely preprocessing textual matter
>>>>(compilation is deferred to after the fact), i guess, so that such
>>>>things are possible. import of modules in python is a different
>>>>beast, so the "redundancy" is (i think) necessary.
>>>>
>>>>any comment/suggestion/idea?
>>>
>>>You're mixed up about this whole idea.
>>>
>>
>>that's why i am asking for advice here.
>>my concern was motivated by a (clumsy) attempt to understand the
>>difference of mechanism between the approach to modular programming in
>>a more "traditional" language (c) and python.
> 
> 
> [Names changed to be valid python module names.]
> 
> I feel I ought to point out that you don't really *have* to import the
> code_3.py in code_1.py. You can get to things code_3.py in code_1.py
> as code_2.code_3.<thing>.
> 

oh. it never occured to me. interesting i must say...

> The semantic behavior of "include" in C is the same as "from module
> import *" in python. Both cases add all the names in the included
> namespace directly to the including namespace. This usage is
> depreciated in Python, because it leads to problems figuring out where
> a specific variable came from. 

so 'import module' is to be preferred, right?

> In C, it creates a problem called "name
> space pollution". This is the case when a file1.c gets all the symbols
> for some_header.h, even though it doesn't include/need those symbols,
> because some header file1.c included needed a symbol from
> some_header.h. This is especially galling if the pollution collides
> with some_header2.h that file1.c actually needs.
> 
>      <mike

thanks a lot, mike!