Minesweeper

Instructions

Your task is to add the mine counts to empty squares in a completed Minesweeper board. The board itself is a rectangle composed of squares that are either empty (' ') or a mine ('*').

For each empty square, count the number of mines adjacent to it (horizontally, vertically, diagonally). If the empty square has no adjacent mines, leave it empty. Otherwise replace it with the adjacent mines count.

For example, you may receive a 5 x 4 board like this (empty spaces are represented here with the '·' character for display on screen):

·*·*·
··*··
··*··
·····

Which your code should transform into this:

1*3*1
13*31
·2*2·
·111·

Exception messages

Sometimes it is necessary to raise an exception. When you do this, you should always include a meaningful error message to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. For situations where you know that the error source will be a certain type, you can choose to raise one of the built in error types, but should still include a meaningful message.

This particular exercise requires that you use the raise statement to "throw" a ValueError when the board() function receives malformed input. The tests will only pass if you both raise the exception and include a message with it.

To raise a ValueError with a message, write the message as an argument to the exception type:

# when the board receives malformed input
raise ValueError("The board is invalid with current input.")