[newbie] confusion concerning fetching an element in a 2d-array

[Dave Angel]

 Jean Dubois <jeandubois314 at gmail.com> Wrote in message:
> Op dinsdag 25 maart 2014 12:01:37 UTC+1 schreef Steven D'Aprano:

>>
>> py> values = [float(s) for s in data.split()]
>> py> print values
>> [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0]
>> py> array_lines = np.array(values)
>> py> array_lines = array_lines.reshape(3, 3)
>> py> print array_lines
>> [[ 1.  2.  3.]
>>  [ 4.  5.  6.]
>>  [ 7.  8.  9.]]
>>
> Dear Steve,
> Thanks for answering my question but unfortunately now I'm totally
> confused. 
> Above I see parts from different programs which I can't
> assemble together to one working program (I really tried hard).
> Can I tell from your comment I shouldn't use numpy?
> I also don't see how to get the value an element specified by (row,
> column) from a numpy_array like "array_lines" in my original code

I don't use numpy,  but I thought Steven's description was clear
 enough.

Your problem was not the extraction,  but the creation of the
 array.  Use print to prove that to yourself. 

> 
> All I need is a little python-example reading a file with e.g. three lines
> with three numbers per line and putting those numbers  as floats in a
> 3x3-numpy_array, then selecting an element from that numpy_array using
> it's row and column-number.

If your instructor wanted you to copy examples,  he would have
 given you one.

First write some code to split and convert each line into floats.
 You don't even try that in your original.  Then do that in a
 loop. Now you have all the floats in one list or array. I presume
 that it's two dimensional.  Use print to check.  If it's not, 
 you'll have to either post process it with a reshape method,  or
 change the way you accumulate it. I can't help with the latter.
 



-- 
DaveA