Re: cx_Oracle cursor.var Example

Thanks a lot for your input, Doug.  That was very helpful.

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Scott S.


-----Original Message-----
From: Doug Henderson [mailto:[email protected]] 
Sent: Thursday, October 23, 2014 6:18 PM
To: cx-oracle-users-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: [cx-oracle-users] cx_Oracle cursor.var Example

On 23 October 2014 14:31, Solomon, Scott \ wrote:
> Ok, getting closer.  Causes another error.  I think I still need to 
> convert variable 'line' to string somehow:
>
>
>   File "C:\Users\{redacted}\gensim\models\lsimodel.py", line 513, in 
> show_topics
>     if i < len(self.projection.s):
>

Your problem is more a python one than a cx_Oracle problem, but i will try to set you on the right path.

Open a python console, and follow along. I am using python3, python2 with "from __future__ import print_function" also works, or just translate the print function calls on the fly.

>>> result = [ ( 'proj 1 title' , ) , ( 'proj 2 title' , ) , ( 'proj 3 
>>> title' , ) , ] result
[('proj 1 title',),('proj 2 title',),('proj 3 title',),]

This is sort of what the result set of the cursor looks like, if you used a statement like

>>> result = cur.fetchall ( )

after executing your cursor. Here, you get back a list of rows, where each row is a tuple of column values. when you use the cursor in the for statement, you are getting back a generator that will give you the next row tuple on each iteration. The actual type of the column values may be cx_Oracle defined types that are automatically converted to regular python strings and number when you use them.

The result of a list comprehension is a generator object. It is almost the same as the list object, in practice. (Not PEP8, to make brackets and parenthesis easier to see.)

>>> print ( row for row in result )
<generator object <genexpr> at 0x0000000002319DC8>
>>> print ( [ row for row in result ] )
[('a',), ('b',), ('c',)]

Notice how I get the column values:
>>> print ( [ row [ 0 ] for row in result ] )
['a', 'b', 'c']
>>> print ( [ row [ 0 ] . upper ( ) for row in result ] )
['A', 'B', 'C']
>>> print ( row [ 0 ] . upper ( ) for row in result )
<generator object <genexpr> at 0x0000000002319D80>

So your corpora.Dictionary() constructor is getting passed a generator object. If it expects a list() type object it may do the wrong thing.
Just add the square brackets to pass a list object instead of the generator object. Likewise, if down in the the guts of that code, something is expecting a string and chokes on the actual type passed back from cx_Oracle, you can convert the value using something like:

>>> print ( [ str ( row [ 0 ] ) . upper ( ) for row in result ] )
['A', 'B', 'C']

Doug

--
Doug Henderson, Calgary, Alberta, Canada

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