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when to use import statements in the header, when to use import statements in the blocks where they are used?

Patto pat.inside at gmail.com
Tue Feb 7 21:38:08 EST 2012 
Dave Angel：


On Wed, Feb 8, 2012 at 10:05 AM, Dave Angel <d at davea.name> wrote:

> On 02/07/2012 08:48 PM, Lei Cheng wrote:
>
>> Hi all,
>>
>>    In a py file, when to use import statements in the header, when to use
>> import statements in the blocks where they are used?
>>    What are the best practices?
>>    Thanks!
>>
>> Pat
>>
>>  Best practice is to put all the imports at the beginning of the module,
> so they are easy to spot.
>
> If you put an import inside a function, it gets re-executed each time the
> function is called, which is a waste of time.  Not too much, since import
> first checks sys.modules to see if it's already loaded.
>
> Also, avoid the     from xxx import *    form, as it pollutes the
> namespace.  And it makes it hard to figure out where a particular name is
> declared.
>
> I believe these and other best practices can be found in pep8.
>
> http://www.python.org/dev/**peps/pep-0008/<http://www.python.org/dev/peps/pep-0008/>
>
> --
>
> DaveA
>
>
yeah, I read pep8.
However I find in the file path/to/djcelery/loaders.py from django-celery
source, there are so many import/from statements used inside functions, I
do not know why the author coded like this. Are there any special facts?
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