[Tutor] Questions regarding class documentation ...

[Lloyd Kvam]

After importing a module, the "stuff" the module provides is referenced
from within the module's namespace.

What you want is:

import sampledict

print sampledict.defaultdict


In general each python source file represents a separate namespace.

hcohen2 wrote:

> Sorry not sure what your is to address you by.  However, your 
> explanation does take care of why the straight import <file name> did 
> not work.  I used the from <file name> import <class name> and it did 
> work.  Nonetheless, having seen so much discussion on why one should not 
> use from ... import ... I thought it odd this seemed necessary.
> 
> I am, however, still bothered by my seeing an instance type()ed as a 
> class and not an instance.
> 
> Thanks,
> Herschel
> 
> orbitz at ezabel.com wrote:
> 
>> When you import a module, you tell python that you will be using these 
>> symbols.  On the 'import' statement, the symbols in your module are 
>> not loaded into the global namespace.  This is good, since there is 
>> always the change of two modules having the same class/function names 
>> in their namespace and you don't want them to conflict.  so when you 
>> do import sampledict, it loads the module but all of the object it 
>> defines are located in the sampledict namespace.  If you were sure you 
>> wanted defaultdict to be imported into the global namespace you could do:
>>
>> from sampledict import defaultdict.
>>
>> now your print defaultdict will work.
>>
>> I hope this helps.
>>
>>
>> On Mon, 26 Jan 2004 09:33:57 -0500
>> hcohen2 <hcohen2 at comcast.net> wrote:
>>
>>  
>>
>>> Because the Core Python Programming book was so out of date regarding 
>>> class and objects discussion I switched over to reading the Alan 
>>> Gauld tutorial on the topic; afterward I directed my attention to the 
>>> documentation on the python.org site.
>>>
>>> [ Here are some facts to keep in mind as you read the discussion 
>>> below: documentation was for version 2.2.3 and I am using 2.2.2.  I 
>>> have so far reproduced the results exactly when I ran it 
>>> interactively.  I am trying to prepare myself to create applications 
>>> independently, hence, I try to go beyond the text samples and use 
>>> more general approaches.]
>>>
>>> Rather than running the code, in section: Subclassing built-in 
>>> types,  interactively I pasted the class definition in a file.  
>>> Moreover, to keep it general I gave the file a name different from 
>>> the class defined in the file, since I would expect I would have many 
>>> unrelated class definitions within a single file that I would load to 
>>> run a custom application.
>>>
>>> So within the python interpreter I imported the file containing the 
>>> defaultdict class:
>>>
>>> >>>import sampledict  # name sampledict.py
>>>
>>> however, when I attempted to run the sample code in the documentation:
>>>
>>> >>> print defaultdict
>>> ...
>>> NameError: name 'defaultdict' is not defined
>>>
>>> Running dir() shows, indeed, 'sampledict' is listed but not 
>>> 'defaultdict, despite the importing of the file that contains the 
>>> latter's definition.
>>>
>>> Perhaps what I did next was due to my having a tenuous grasp on this 
>>> topic I remembered the problems with unbound method discussion.  
>>> Hence, I tried to created an instance, but I got the same error.  At 
>>> that point I became suspicious of the success the importing command.  
>>> Though I know it is bad style and a command to be avoided I gave the 
>>> command:
>>>
>>> >>> from sampledict import defaultdict
>>> >>> print defaultdict
>>> <class 'sampledict.defaultdict'>
>>> >>> dictIns = defaultdict()
>>> >>> print dictIns
>>> {}
>>> >>> type(dictIns)
>>> <class 'sampledict.defaultdict'>
>>>
>>> Now the print dictIns 'works', but I have a number of questions!
>>>
>>> Again the interactive reproduction of the code works exactly as 
>>> described (as far as I have gone).  While I can reproduce the 
>>> results, why doesn't the simple import command work for the file?  
>>> What happened to seeing an instance rather than the type now being 
>>> class for dictIns?
>>>
>>> Could someone enlighten me regarding these questions without citing 
>>> further documentation that might just add to my confusion as to what 
>>> may be happening.  When I created instances previously that were 
>>> identified as instances not as a class.  [Regarding the last 
>>> statement: on this machine with this version of Python.]
>>>
>>> It is very difficult to gain a firm grasp of this topic when the 
>>> results are so haphazard and not internally consistent.
>>>
>>> I would like to thank anyone that can clarify why I have run into 
>>> these difficulties.
>>>
>>>
>>> _______________________________________________
>>> Tutor maillist  -  Tutor at python.org
>>> http://mail.python.org/mailman/listinfo/tutor
>>>   
>>
>>
>> _______________________________________________
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>> http://mail.python.org/mailman/listinfo/tutor
>>
>>  
>>
> 
> 
> 
> _______________________________________________
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> 

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