debugging - How do I fix my Python sudoku solver bug? -

this homework

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hello. had make python sudoku solver , came with.

http://pastebin.com/jrkaqsed (includes input , output get)

however, when run it, first populate call causes error below. seems add 1 2 cells @ same time.

0 5 9 0 0 0 4 8 3 #current row being tested add, 1 #number add 0 5 #row, column 0 5 9 0 1 1 4 8 3 #row outputs 

i can't figure out why doing that. appreciated.

thank you

edit:

i found bug. generating rowset @ start of each row , therefore didn't know if number had been used.

however, code still doesn't finish sudoku grid

i can't replicate error get, there's problem how read in sudoku grid.

0 5 9 0 0 0 4 8 3 0 0 0 0 0 0 0 1 2 0 1 0 0 2 8 0 0 0 0 9 8 0 7 4 0 2 0 0 4 0 0 8 0 0 3 0 0 7 0 6 3 0 5 4 0 0 0 0 1 6 0 0 5 0 6 2 0 0 0 0 0 0 0 7 3 5 0 0 0 8 6 0 

reading in file way do:

fi = open("sudoku.txt", "r") infile = fi.read() grid = [list(i) in infile.split("\n")] 

this creates grid that's list of lists, not 1 expect. example, here's first line:

['0', ' ', '5', ' ', '9', ' ', '0', ' ', '0', ' ', '0', ' ', '4', ' ', '8', ' ', '3']

instead of reading file string , splitting on newline, can loop through open file object , split each line in split on space.

fi = open("sudoku.txt", "r") grid = [] line in fi:     grid.append([int(i) in line.split(" ")]) 

so think problem related spaces still being present in grid, because after fixing (and problem regarding oldgrid somewhere), solves sudoku.