Python, list index out of range in a 2D array

Question

I'm new to Python and running into a heap of problems and I need some help. I have a python function that needs to parse through some simple values with 0s and 1s.

I need to store each 0s with a 2D array so the positions can be referenced later. But I'm getting a index out of range, what am I doing wrong and how to fix it?

Here's the python code:

def storeSubset(fileName):
locale = dataParser(fileName); test = [];
subset = []; subSetCount = 0; columnCt =0;
rowList = []; columnList=[];
for rowCount in range(0, len(locale)):
#   print " "; print " "
#   print "Values of one row locale[row]: ", locale[rowCount]; 
#   print "We are at row# 'row': ", rowCount;
#   print "Length of row is int(len(locale[rowCount]))", int(len(locale[rowCount]));
    test = locale[rowCount];

    for columnCount in range (0, int(len(locale[rowCount])-1)):
        rowVal = locale[rowCount][columnCount];
#       print "Value of column is :", rowVal;
        if (rowVal==0):
#           print "columnVal = 0, the column position is ", columnCount;
            subset[subSetCount].append(rowList[rowCount]);
            subset[subSetCount].append(rowList[columnCount]);
subSetCount+=1;
print "The Subsets is :", subset;
return subset;

@David has the answer covered, but as a side note (that will save you some typing!) - you don't have to use semicolons to end a line in Python. Also, take a look at the docs on looping techniques (docs.python.org/tutorial/datastructures.html#tut-loopidioms) - you can actually use syntax like for rowCount in locale: to iterate over each item in locale (so then you would have test = rowCount, etc.). — RocketDonkey
– RocketDonkey, Commented Aug 22, 2012 at 1:07

David · Accepted Answer · 2012-08-22 01:06:00Z

3

When you have subset[subSetCount], subset is still an empty list, so the index is out of range. The same is true for rowList[rowCount] and rowList[columnCount].

From here, I'll speculate a little about what you're trying to do to help you fix it. It seems like maybe instead of

subset[subSetCount].append(rowList[rowCount]);
subset[subSetCount].append(rowList[columnCount]);

you just want

rowList.append( rowCount )
columnList.append( columnCount )

Then, after the for columnCount loop, maybe you want

subset.append( [rowList, columnList] )

or something like that.

edited Aug 22, 2012 at 1:06

answered Aug 22, 2012 at 0:57

David

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lively · Accepted Answer · 2012-08-22 00:58:33Z

1

I'm not 100% certain exactly what you're trying to do, so I'm just stabbing in the dark here.

subset[subSetCount].append(rowList[rowCount]);
subset[subSetCount].append(rowList[columnCount]);

This seems problematic. You're appending to an index, but I don't see how this index has anything in it. I'm assuming this is the issue. Perhaps just

subset.append(rowList[rowCount])

would accomplish what you what.

Also, you don't need semicolons =D

answered Aug 22, 2012 at 0:58

lively

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mgilson · Accepted Answer · 2012-08-22 01:02:45Z

1

This is an occasion where numpy would be useful:

import numpy as np
with open(datafile) as f:
     lines = [list(l.strip()) for l in f]

array = np.array(lines)
zeros = array == 0
ones = array == 1

answered Aug 22, 2012 at 1:02

mgilson

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