Shortest path in a grid

def shortest_path(grid: list[list[int]], start: tuple[int,int], target: tuple[int,int]) -> int:
    from collections import deque
    queue = deque([(start, 0)])
    seen = {start}
    while queue:
        (r, c), distance = queue.popleft()
        if (r, c) == target:
            return distance
        for dr, dc in ((1,0),(-1,0),(0,1),(0,-1)):
            nr, nc = r + dr, c + dc
            if 0 <= nr < len(grid) and 0 <= nc < len(grid[0]) and not grid[nr][nc] and (nr,nc) not in seen:
                seen.add((nr,nc)); queue.append(((nr,nc), distance+1))
    return -1