How to import only one module in a package when the package __init__.py has already imports the modules?

[Peng Yu]

On Sat, Oct 31, 2009 at 9:34 PM, Steven D'Aprano
<steve at remove-this-cybersource.com.au> wrote:
> On Sat, 31 Oct 2009 18:29:35 -0500, Peng Yu wrote:
>
>> If two functions are too long to put in file, I generally put them in
>> two different files.
>
> If two functions are too long for a single file, the functions are too
> big and need to be broken up into ten or thirty sub-functions each!
>
> Ideally, no function should be more than ten or twenty lines (plus
> docstring), certainly no more than a page. In a language like Python that
> is so compact, monster functions that are hundreds of lines long is
> almost certainly inexcusable.
>
>
>> And I always put a single class in a file.
>
> An unnecessary and silly restriction. It is reasonable for large
> complicated classes, but not a rule for all classes, some of which might
> be as small as two lines.
>
>
>> Suppose that I have many functions in one file, it is not clear to see
>> how many functions are in the file at first glance.
>
> So what? Why is it import to see how many functions are in the file?
>
>
>
>> If I put each function in its
>> own file,  just by looking at the directory structure, I can easily see
>> how many functions there are.
>
> Why do you care how many functions there are?

Because I want to easily see what functions are there.

>> One advantage is on refactoring. When each function has its own file, I
>> can change variable names, etc., for a give function without worrying
>> accidentally change variable names in other functions.
>
> Do you understand that each function has it's own local namespace? Unless
> you are foolish enough to use global variables for everything, you can
> refactor any given function without effecting other functions in the same
> file.
>
>
>> When I find a
>> function is more appropriate to put in another namespace, I can just
>> move the file around.
>
> A module is a namespace.

This is a constrain imposed by python. C++ does not have this
constraint, so I can have each class in a file without any
complication in calling classes.

Because of this constraint in python. I have do something

from spam import spam

or

call spam.spam.

>> Another advantage is on testing. I can have associated test dir for each
>> class or function. By this way I can easily locate the definition and
>> the test to track any potential problems.
>
> You can do this when functions share the same file.
>
>
>> You can use package rather than module to group semantic related classes
>> and functions.
>
> Python makes available many namespaces:
>
> Function
> Module
> Package
>
> You are artificially restricting yourself to use:
>
> Function = Module
> Package
>
> and that's supposed to be an advantage???

Since Module = file, by making Function = Module and Class = Module,
it simplifies the search of a function and a class. I also put the
testing code along with the module, which make it easier to move
module across packages (when I do refactoring, sometime I found some
module is not appropriate to put in a package anymore, so I need to
move it to a better package).