[Baypiggies] Fwd: A beginner's question on python class

[Yiou Li]

Thanks to all for your replies!

Leo

On Mon, Feb 20, 2012 at 3:45 PM, Lincoln Peters <anfrind at gmail.com> wrote:
> On Mon, Feb 20, 2012 at 2:02 PM, Yiou Li <liyiou at gmail.com> wrote:
>> My question is, since I import a function "sample" from the library
>> "random" in myClass, do I have to import "sample" in my main script as
>> well?
>>
>> --- I did a debugging experiment using the following code to see that
>> the library "random" was imported at myClassInstance.myFunction(),
>> therefore, the answer to my question is -- I don't have to import the
>> "random" library in the main script. And the import statement is just
>> like a #include statement in C.
>
> Short answer: yes, you have to import random even if another module
> you imported already imports random.
>
> Long answer: "import" is similar to "#include", but not identical.  In
> general, each .py or .pyc file represents a module, and each import
> statement makes the contents of one module available from within the
> importing module.  However, unlike #include, the import command
> doesn't add the contents of the other module to the importing module's
> namespace, but rather creates a reference to it that behaves similarly
> to a C++ namespace (e.g. import random; random.shuffle(...)).  One
> consequence of this is that if you want to import modules A and B, and
> module B already imports module A, you need to either explicitly
> import both modules, or you have to refer to module B to get to module
> A (i.e. B.A.function instead of A.function).  Most of the time,
> importing both modules is the preferred solution.
>
> Note that importing a module multiple times will NOT cause multiple
> copies of it to be made in memory; the Python interpreter is smart
> enough to recognize that a module has already been imported and will
> just create a new reference to it.
>
> Disclaimer: this is a highly simplified explanation, and omits several
> nuances of how importing works in Python.  For 99% of Python
> development, however, you don't need to worry about those nuances.
>
>
> Hope this helps.
>
>
> --
> Lincoln Peters
> <anfrind at gmail.com>
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