Reading File Into 2D List

Dave Angel davea at davea.name
Tue Jul 9 16:24:06 CEST 2013


On 07/09/2013 09:30 AM, alex.hanga at gmail.com wrote:
> Hello!
>
> I'm new here and fairly new to Python. I am attempting to read a data file into python and adding it to a 2D list to make it easy to use further down the line.
>
> My data file is just 7 numbers in a row seperated by commas and each bulk of data is seperated by the sign @ to indicate that the data from this point on should be stored into a new part of the 2D list.
>
> 1,1,1,1,1,1,1
> 2,2,2,2,2,2,2
> @
> 3,3,3,3,3,3,3
> 4,4,4,4,4,4,4
>

Perhaps you mean:
data = """\
1,1,1,1,1,1,1
2,2,2,2,2,2,2
@
3,3,3,3,3,3,3
4,4,4,4,4,4,4
"""




> After reading the file, the way I imagine the data to be shown would be in this manner:
>
> data[0][0] = (1,1,1,1,1,1,1)
> data[0][1] = (2,2,2,2,2,2,2)
> data[1][0] = (3,3,3,3,3,3,3)
> data[1][1] = (4,4,4,4,4,4,4)

perhaps you mean:
object_data[0][0] == (1,1,1,1,1,1)
etc.

>
> This way it will be easy to loop across the data when I use it in Blender.
>
> My code looks like this;
>
> ------------------------------
> object_data = []
> object_data.append([])

You omitted   i = 0
>
> for rows in data.splitlines():

So exactly what is data?  It's not what you say above.  Did you get it 
by doing something like myfile.read() ?


>      elems = rows.split(',')
>      if elems[0] != "@":
>         object_data[i].append((float(elems[0]),float(elems[1]),
>         float(elems[2]),float(elems[3]),float(elems[4]),
>         float(elems[5]),int(elems[6])))
>      else:
>
>          **start on object_data[1][j] and loop over it all again**
> -------------------------------
>
> I could really use some help as to how I would force my code to not start on object_data[0] on the next iteration in the for loop, but rather on object_data[1]. I'm an avid Matlab user so I imagined this to be done simply by setting i=i+1 in the else part, however this does not work as it complains about the list being out of bounds.
>
> Any help is really appreciated!
>

Replace te **start line with something like:

            object_data.append([])
            i += 1

This assumes a few missing lines, which must have been there or you 
would have already had runtime errors.  For example, you'll need i=0 
before the loop.

Another comment about the append with all those calls to float().  When 
you see a line like that, you want to seriously consider making it a 
loop, or a comprehension, or something.

Given that elem is a list of strings, you could convert it to a list of 
float, then convert that to a tuple (if you really wanted that).  At 
that point, you just append it.  All this could be done in one line if 
you like, something like (untested):

      object_data[i].append(tuple(map(float, row.split(","))))



-- 
DaveA




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