Sudoku is a logic-based number placement puzzle that consists of 81 cells which are divided into 9 columns, rows and blocks. The goal of this game is to fill out each cells with numbers 1–9 so that there are no repeating numbers in each row, column and blocks. In this post, I aim to introduce a digit recognition and integer linear programming based automatic sudoku solver that uses the following: Keras (based on the MNIST database [1]) and OpenCV for digit recognition and PuLP for integer linear programming. The database is also widely used for training and testing in the field of machine learning. In this section, I explain the overview of image processing for digit recognition.