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importing module versus using function?

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  importing module versus using function? gujax <rjngrj2010@gmail.com> - 2012-01-31 07:08 -0800
    Re: importing module versus using function? Robert Kern <robert.kern@gmail.com> - 2012-01-31 15:53 +0000

#19642 — importing module versus using function?

Hi,
I am confused on this quite bad!!
If I have this typed in interactive python:

>>import numpy

>>def dummy():
   y=numpy.arange(1,2,0.1)
   return y

and then
>>s = dummy()
>>s
>>array[1. , 1.1,  1.2........]

 it works.

But if I have a module called example.py, whose code is

def dummy():
   y=numpy.arange(1,2,0.1)
   return y

and now if I do the following:

>>import numpy
>>from example import *
>>s=dummy()

The above sequence does not work. It gives an error saying global
variable numpy not defined.

I understand that when I import a module it gets imported after
getting compiled and therefore, the module should
have a statement "import numpy" at its start.

But what if I just want to use the function 'dummy'?

I tried the following:
from example import dummy
and then try to use the function, it still gives me 'global name numpy
not defined'!

Why is that happening?
Any pointers please.
Thanks

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#19643

On 1/31/12 3:08 PM, gujax wrote:
> Hi,
> I am confused on this quite bad!!
> If I have this typed in interactive python:
>
>>> import numpy
>
>>> def dummy():
>     y=numpy.arange(1,2,0.1)
>     return y
>
> and then
>>> s = dummy()
>>> s
>>> array[1. , 1.1,  1.2........]
>
>   it works.
>
> But if I have a module called example.py, whose code is
>
> def dummy():
>     y=numpy.arange(1,2,0.1)
>     return y
>
> and now if I do the following:
>
>>> import numpy
>> >from example import *
>>> s=dummy()
>
> The above sequence does not work. It gives an error saying global
> variable numpy not defined.
>
> I understand that when I import a module it gets imported after
> getting compiled and therefore, the module should
> have a statement "import numpy" at its start.
>
> But what if I just want to use the function 'dummy'?

You need to import numpy in dummy.py. When a function needs to look up a name, 
it goes to the module's namespace in which the function is defined, not one of 
the many namespaces where the function is called from.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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