[Tutor] Question about writing to Excel with slavic characters

[Marko Limbek]

Hi Walter

It is as you say. Thanks for long explanation.
I am using the newer version.
Now I also understand difference between single underscore and double
underscore. I would still have problems if I would want to programme
them for instance.

Well I always try to be independent and I want to answer the questions
by myself. Learning the tutorial by heart is also not my way. Maybe I
need just to understand it better and understand better the whole
philosophy of private and public methods. And what is __init__ method
and __enter__ method and so on.
I was just asking of that getNumberofVariables() method, because I
wanted to run the methods my self and see if I get the labels I wanted
by myself. I wouldn't want to ask the author directly does this
programme does this or that because that might be silly questions
because the answer would be, 'well of course it does, run this and
this method' and you will see. I don't want to consume too much time
of the people. So I wanted to check first. As an amateur as I am.
Nobody really trained me how to programme except for in the first
years at the faculty some 10 years ago, but at that time I was not
that interested in programming.

Now we are resolving the issue directly with Albert.

Have a nice day,
Marko


On Fri, Mar 9, 2012 at 11:49 AM, Walter Prins <wprins at gmail.com> wrote:
> Hi Marko,
>
> On 9 March 2012 08:34, Marko Limbek <marko.limbek at valicon.net> wrote:
>>  File "C:\Dropbox\Exc_MarkoL_Zenel\Python\crosstabs\src\src\rw.py",
>> line 715, in <module>
>>    mySavReaderObject.getNumberofVariables(savFileName,
>> mySavReaderObject.fh, mySavReaderObject.spssio)
>> AttributeError: 'SavReader' object has no attribute 'spssio'
>>
>> So the methods must really be somewhat internal.
>
> Python doesn't enforce access levels like some other languages do
> which means effectively, any member of any object can in principle be
> accessed.  By "gentlemans agreement", members with a name starting
> with a single underscore are supposed to be considered private
> (although you can still ignore this agreement and access them anyway)
> while members with double underscores get some behind the scenes
> assistance to ensure privateness and name uniqueness via "name
> mangling".  (There's a couple of other minor behavioural differences,
> but the point stands -- there's no preventing you as programmer from
> accessing "private" members of a class if you insist to do so.  But
> then it's doubly your problem if that gets you into trouble ;) )
>
> Anyway, the message then really means what it says -- The SavReader
> object instance you're using really does not have an spssio member
> (there should be no problem accessing it if it was there so I must
> interpret that message to mean what it says.)   I'm not sure why this
> would be the case -- perhaps we're not looking/using the same version
> of the reader class and the member name has changed?  (I previously
> guessed/assumed  that you were using the following version, or
> something close enough to it, given here:
> http://code.activestate.com/recipes/577650-python-reader-for-spss-sav-files/
>  Looking back I see you're actually using a slightly newer version
> from here: http://code.activestate.com/recipes/577811-python-reader-writer-for-spss-sav-files-linux-mac-/
> But, everything I've said appears to still hold true about the updated
> version, so can you clarify which version you're currently using?)
>
> Regardless, the error simple enough to troubleshoot -- have a look at
> *your* version of the SavReader class, and find out what the member
> name should in fact be.  There are calls to e.g.
> getNumberofVariables() in the class itself, from which you can
> determine what the object data/field/variable member is that holds the
> value to pass to the spssio parameter of getNumberofVariables().
>
> But, I have to repeat: The value that you get from
> getNumberofVariables() is the exact same value that you get inside of
> the numVars variable after calling:
>
>  numVars, nCases, varNames, varTypes, printTypesFile,
> printTypeLabels, varWids = mySavReaderObj.getSavFileInfo()
>
> You can see this will be the case if you read the code:
> 1) The __init__ method assigns self.numVars_ from the result of
> calling self._readBasicSavFileInfo().
> 2) This in turn calls on self.getNumberofVariables() as follows:
>  numVars = self.getNumberofVariables(self.fh, self.spssio)[1]
> ... and that local variable numVars is what is returned and ends up in
> the object member self.numVars_.
> 3) Then, looking at getSavFileInfo() you can see that it in turn
> simply returns self.numVars_,
> 4) In other words it returns the same value that it previously
> retrieved using self.getNumberofVariables().
>
> So, the 2 ways are functionally identical w.r.t. the retrieval of the
> "NumberofVariables".  The only differences are that a) with the latter
> call you get a bunch of other stuff besides the number of variables,
> and b) With the latter call you don't have to worry about spssio or fh
> parameters (because they're absent/not required when calling
> getSavFileInfo() and c) with the latter call the actual retrieval of
> the number of variables happened slightly earlier on when the
> SavReader object was created, while with the direct call to
> getNumberofVariables() it is presumably read again directly from the
> file.
>
> So, I think you need to stop fixating on the getNumberofVariables()
> method as it's not, I suspect, the solution to your real problem like
> you seem to think, and it is also introducing a distraction (the
> parameters issue) since it's not really the intended way for you to
> use this class.  (Not that you absolutely cannot use it if you're
> determined to do so, as I've already tried to explain, but it's just
> probably just easier to go with the intended means of use for now
> given that there's functionally no difference in the result up to this
> point, at least that I can see.)
>
> Walter
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