Returning all "positions" of a list

I Have a list with "a" and "b" and the "b"'s are somewhat of a path and "a"'s are walls. Im writing a program to make a graph of all the possible moves. I got the code running to check the first "b" for possible moves, but i ha开发者_运维知识库ve NO Idea how im going to find all "b"'s , even less check them all without repeating.

Major issue im having is getting the tuple coordinates of the "b"'s out of the list.

Any pointers/tips?

grid = [['b','a','b'],['b','b','b'],['a','a','a']
results = []
for row in range(len(grid)):
  for col in range(len(grid[row])):
    if grid[row][col] == 'b':
      results.append((row, col))

print results

There's probably some better way of doing it using maps but its been awhile since I've used Python.

+1 to Nemo157 for his answer. If you want the exact same code, but in one line, it can be done as follows:

grid = [['b','a','b'],['b','b','b'],['a','a','a']
[(row, col) for row in range(len(grid)) for col in range(len(grid[row])) if grid[row][col] == 'b']

Cheers!

This finds a list of valid moves from every square.

I am assume that off the edge of the map is a "wall", and that you can't move diagonally:

# reference like this: maze[y][x] or maze[row][col]
# with [0][0] starting at the top left
maze = [['b','a','a', 'a'],
        ['b','a','b', 'a'],
        ['b','a','b', 'b'],
        ['b','b','b', 'a'],
        ['b','a','b', 'a'],
        ['a','a','a', 'a']]

moves = {}

# Loop through all cells of the maze, starting in the top-left
for y, row in enumerate(maze):
    for x, value in enumerate(row):
#        print "y, x, val: ", y, x, value
        # for every cell, create an empty list of moves
        moves[y, x] = []
        # then if we can move from this cell
        # check each of its neighbours and if they are a 'b' add it 
        # to the list of moves - assumes we can't move diagonally
        if value == 'b':
            if y - 1 > 0 and maze[y - 1][x] == 'b':
                moves[y, x].append((y - 1, x))
            if y + 1 < len(maze) and maze[y + 1][x] == 'b':
                moves[y, x].append((y + 1, x))
            if x - 1 > 0 and maze[y][x - 1] == 'b':
                moves[y, x].append((y, x - 1))
            if x + 1 < len(row) and maze[y][x+1] == 'b':
                moves[y, x].append((y, x+1))

print moves