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.
You say first that "[code-1] uses names from both", which by definition means that it needs to import both. (I say by definition because import is *how* a module gets names from another module.)
Then you say that code-1 can choose not to include code-3 because some other module is including it... but so what? That doesn't change the fact that code-1 needs names from code-3, and just because code-3 is imported elsewhere is no reason to think that code-1 magically gets its names too. Should all modules magically see all names in all modules which are imported, even by other modules?
that's how inclusion works in c, which is why i asked for clarification about the differences between c-style includes and python-style imports.
now i can see that python-style import is more like the inclusion of declarations in c (the "names"), usually shipped as *.h header files.
the real *definition* of names is python (contents of variables, definition of functions, and so on) i guess is inserted later in the process of execution.
That would pretty much defeat most of the value of namespaces.
Anyway, why this concern over so-called redundant imports? The source code itself is not parsed and compiled all over again, and even the .pyc file is not re-read... once any module has imported a module any other import just retrieves a reference to that module from the sys.modules dictionary, which is practically a free operation.
-Peter
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.
thanks again for your couseling.
bye
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