The code is missing one of the "groups". There should be 27 (one for each of the 9 rows, columns and 3x3 squares), but there are only 26. The missing one is the column [8 ... 80].<p>Probably the most famous Sudoku program is Peter Norvig's, also written in Python:<p><a href="http://www.norvig.com/sudoku.html" rel="nofollow">http://www.norvig.com/sudoku.html</a>
In my opinion the most impressive sudoku solver in Python is the one using Z3: <a href="http://rise4fun.com/Z3Py/tutorialcontent/guide#h210" rel="nofollow">http://rise4fun.com/Z3Py/tutorialcontent/guide#h210</a><p>Less than 30 lines of code just specifying what is a Sudoku game is!
A few years ago I wrote a sudoku solver using the Knuth Dancing Limks algorithm. It's kind of a fun project, and I included an option to output the board as it recurses.<p><a href="http://cavernum.net/dlsudoku/" rel="nofollow">http://cavernum.net/dlsudoku/</a>