# [PyAR2] TypeError: 'int' object is not subscriptable

Carl Burch dr.cburch at gmail.com
Sun Aug 21 20:54:14 CEST 2011

```Yes, you access an element with r[i][j], since after all a 2d array is just the same as a list of lists; r[i] is a single one of those lists, and you'd add [j] to extract an element from that list.

To go further beyond what you ask: It's also interesting how you can do the same thing with list comprehensions:

col[0] = [r[0] for r in row]

Here, r iterates through each row in the row array, and we build up an array of all the r[0]'s.

You could repeat this same line 8 more times, but I'd put it into a loop:

for i in range(9):
col[i] = [r[i] for r in row]

Or we could even nest the comprehension into another comprehension:

col = [[r[i] for r in row] for i in range(9)]

Maybe somebody else has an even cleverer way to build up the translation of a 2d array.

-Carl

On Aug 21, 2011, at 12:20 PM, Coltrey Mather <pyar2 at cowsgomoo.org> wrote:

>
> On Aug 21, 2011 9:04 AM, "Daniel Veazey" <daniel at danielveazey.com> wrote:
> > In my efforts to learn Python, I'm trying to write a program to solve a
> > Sudoku puzzle. Here is the code I have so far:
> >
> > ## define and populate the board by rows; 0 = unsolved position
> > row = [0, 1, 2, 3, 4, 5, 6, 7, 8]
> > row[0] = [5, 6, 0, 0, 4, 1, 0, 0, 8]
> > row[1] = [1, 0, 0, 0, 0, 9, 0, 7, 0]
> > row[2] = [0, 8, 0, 5, 0, 2, 3, 0, 0]
> > row[3] = [3, 0, 9, 0, 2, 0, 0, 5, 0]
> > row[4] = [0, 7, 0, 3, 0, 5, 0, 9, 0]
> > row[5] = [0, 5, 0, 0, 7, 0, 6, 0, 1]
> > row[6] = [0, 0, 2, 1, 0, 3, 0, 6, 0]
> > row[7] = [0, 3, 0, 2, 0, 0, 0, 0, 9]
> > row[8] = [6, 0, 0, 4, 5, 0, 0, 8, 3]
> >
> > ## define and populate the columns by referring to the rows
> > col = [0, 1, 2, 3, 4, 5, 6, 7, 8]
> > col[0] = [row[0[0]], row[1[0]], row[2[0]], row[3[0]], row[4[0]], row[5[0]],
> > row[6[0]], row[7[0]], row[8[0]]]
> > col[1] = [row[0[1]], row[1[1]], row[2[1]], row[3[1]], row[4[1]], row[5[1]],
> > row[6[1]], row[7[1]], row[8[1]]]
> > col[2] = [row[0[2]], row[1[2]], row[2[2]], row[3[2]], row[4[2]], row[5[2]],
> > row[6[2]], row[7[2]], row[8[2]]]
> > col[3] = [row[0[3]], row[1[3]], row[2[3]], row[3[3]], row[4[3]], row[5[3]],
> > row[6[3]], row[7[3]], row[8[3]]]
> > col[4] = [row[0[4]], row[1[4]], row[2[4]], row[3[4]], row[4[4]], row[5[4]],
> > row[6[4]], row[7[4]], row[8[4]]]
> > col[5] = [row[0[5]], row[1[5]], row[2[5]], row[3[5]], row[4[5]], row[5[5]],
> > row[6[5]], row[7[5]], row[8[5]]]
> > col[6] = [row[0[6]], row[1[6]], row[2[6]], row[3[6]], row[4[6]], row[5[6]],
> > row[6[6]], row[7[6]], row[8[6]]]
> > col[7] = [row[0[7]], row[1[7]], row[2[7]], row[3[7]], row[4[7]], row[5[7]],
> > row[6[7]], row[7[7]], row[8[7]]]
> > col[8] = [row[0[8]], row[1[8]], row[2[8]], row[3[8]], row[4[8]], row[5[8]],
> > row[6[8]], row[7[8]], row[8[8]]]
> >
> > When I run the program, the first part of defining the rows runs fine, but
> > when I start to define the columns, I get this error:
> >
> > Traceback (most recent call last):
> > File "sudoku_solver_1.py", line 15, in <module>
> > col[0] = [row[0[0]], row[1[0]], row[2[0]], row[3[0]], row[4[0]],
> > row[5[0]], row[6[0]], row[7[0]], row[8[0]]]
> > TypeError: 'int' object is not subscriptable
> >
> > I'm not quite sure what I'm doing wrong here. I want to nest a list inside
> > the list col by referring to the nested lists in row. Any tips on why I'm
> > getting this error or what I should do to fix it?
> >
> > Thanks,
> > Daniel
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