Not sure with what the code is doing

Question

is anyone able to decipher this code and help explain how the code allows the knight to move across the board it would be appreciated. i don't really have any idea as to why these specific numbers so if you could also explain that, it would be appreciated.

# Notes - variables:
# chosen is the current position of the piece
# moves is a list of where the chosen piece can move
# taken_pieces is a list of where the chosen piece can capture
# board is a list of every space on the board and says what piece exists there
# turn is a number either 1 or 2 representing whose turn it is

turn = 1
wcastle = 0
bcastle = 0
chosen = None
moves = []
taken_pieces = []
wtake_piece = []
btake_piece = []
board = [None for i in range(64)]

def attacked_spaces(player,board):

attacked = []

    # Knight for both players
    if board[i][0] == 'N' and board[i][1] == str(player):
        x,y = i%8,i//8

        if x >= 2 and y <= 6:
            attacked.append((x-2)+(y+1)*8)
        if x >= 1 and y <= 5:
            attacked.append((x-1)+(y+2)*8)

        if x <= 6 and y <= 5:
            attacked.append((x+1)+(y+2)*8)
        if x <= 5 and y <= 6:
            attacked.append((x+2)+(y+1)*8)

        if x <= 5 and y >= 1:
            attacked.append((x+2)+(y-1)*8)
        if x <= 6 and y >= 2:
            attacked.append((x+1)+(y-2)*8)

        if x >= 1 and y >= 2:
            attacked.append((x-1)+(y-2)*8)
        if x >= 2 and y >= 1:
            attacked.append((x-2)+(y-1)*8)

    if board[i][0] == 'K' and board[i][1] == str(player):
        x,y = i%8,i//8

        if x >= 1 and y <= 6:
            attacked.append((x-1)+(y+1)*8)
        if y <= 6:
            attacked.append(x+(y+1)*8)
        if x <= 6 and y <= 6:
            attacked.append((x+1)+(y+1)*8)
        if x <= 6:
                attacked.append((x+1)+y*8)
        if x <= 6 and y >= 1:
            attacked.append((x+1)+(y-1)*8)
        if y >= 1:
            attacked.append(x+(y-1)*8)
        if x >= 1 and y >= 1:
            attacked.append((x-1)+(y-1)*8)
        if x >= 1:
            attacked.append((x-1)+y*8)

return attacked

Answer 1

It's a standard way of finding all squares that a knight is attacking on a board represented internally one-dimensionally. There are 8 separate cases. Here is some perl I wrote recently that does basically the same thing:

for ($i=0,$k=0; $i<$s; ++$i) {
  for ($j=0; $j<$s; ++$j,++$k) {
    my @moves;
    if ($i>1) {
      if ($j>0) { push @moves, $k-$s-$s-1 }
      if ($j<$s-1) { push @moves, $k-$s-$s+1 }
      }
    if ($j>1) {
      if ($i>0) { push @moves, $k-$s-2 }
      if ($i<$s-1) { push @moves, $k+$s-2 }
      }
    if ($i<$s-2) {
      if ($j>0) { push @moves, $k+$s+$s-1 }
      if ($j<$s-1) { push @moves, $k+$s+$s+1 }
      }
    if ($j<$s-2) {
      if ($i>0) { push @moves, $k-$s+2 }
      if ($i<$s-1) { push @moves, $k+$s+2 }
      }