[hrzn]

A few years back I made a modest attempt at writing a concise yet readable sudoku solver in Python - in about 29 lines: https://github.com/hrzn/sudoku/blob/master/sudoku.py

Could have been made shorter at the price of readability.

[forgotpwd16]

Looks nice. Since imports numpy can utilize (more of) numpy's operations to squeeze validation functions and nested fors to one. Should result in shorter code but readability will probably depend on reader's experience in array programming.