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Sudoku Solver in pure Python with no dependencies

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Sudoku Solver written in pure Python with no dependencies.

It solves Sudokus of sizes N x N by pure induction as far as is possible, and then uses an optional Dancing Links solver, which is a brute force methodology, when the basic induction is not enough.


Install by calling:

pip install git+


Tests can be run using nosetests:

nosetests tests

The tests make a HTTP request to a file containing several Sudokus on Project Euler.


A Sudoku stored in a file can be solved as such:

from dlxsudoku import Sudoku

s = Sudoku.load_file('path/to/sudoku.sud')
s.solve(verbose=True, allow_brute_force=True)

Alternatively, if your Sudoku is stored in string variable it can be solved in the following fashion:

from dlxsudoku import Sudoku

sudoku_string_1 = "030467050920010006067300148301006027400850600090200400005624001203000504040030702"
sudoku_string_2 = "# Example Sudoku\n" + \
                  "*72****6*\n" + \
                  "***72*9*4\n" + \
                  "*9*1****2\n" + \
                  "*******4*\n" + \
                  "82*4*71**\n" + \
                  "**9*6*8**\n" + \
                  "***9**6**\n" + \
                  "**3*72*9*\n" + \

s1 = Sudoku(sudoku_string_1)

s2 = Sudoku(sudoku_string_2)

Sudoku formatting

A Sudoku file or string should be structured in the following manner:

# Optional comment or metadata

or as a one-liner:


Any character other than [1-9] may be used as a placeholder for unknowns.

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