CODEWITHSUNDEEP
python-3.x
Bovojon A
Bovojon A

Reputation: 35

Why is Python giving AttributeError even when the attribute does exist

I am trying to create a class Tile and use it in another method. However, when I run the code (below), the error is raised: AttributeError: type object 'Tile' has no attribute 'row'.

As I pop the class from the queue (Python list) and try to print it, it prints the value of the row (which is 0) but then gives the AttributeError.

Why is it saying that the attribute row does not exist?

"""
Shortest distance between two cells in a matrix or grid

"""

class Tile:
  def __init__(self, row, col, dist):  
    self.row = row
    self.col = col
    self.dist = dist

def min_path(rows, cols, lot):
  start_node = Tile(0, 0, 0)
  q = []
  q.append(start_node)
  visited = [[False]*cols for i in range(rows)]

  for i in range(rows):
    for j in range(cols):
      if lot[i][j] == 0:
        visited[i][j] = True

  while q:
    new_tile = q.pop(0)

    print(new_tile.row)

    if lot[new_tile.row][new_tile.col] == 9:
      return new_tile.dist

    if new_tile.row - 1 >= 0 and visited[new_tile.row - 1][new_tile.col] == False:
      Tile(new_tile.row - 1, new_tile.col, new_tile.dist + 1)
      q.append(Tile)
      visited[new_tile.row - 1][new_tile.col] = True

    if new_tile.row + 1 < rows and visited[new_tile.row + 1][new_tile.col] == False:
      Tile(new_tile.row + 1, new_tile.col, new_tile.dist + 1)
      q.append(Tile)
      visited[new_tile.row + 1][new_tile.col] = True

    if new_tile.col - 1 >= 0 and visited[new_tile.row][new_tile.col - 1] == False:
      Tile(new_tile.row, new_tile.col - 1, new_tile.dist + 1)
      q.append(Tile)
      visited[new_tile.row][new_tile.col - 1] = True

    if new_tile.col + 1 < cols and visited[new_tile.row][new_tile.col + 1] == False:
      Tile(new_tile.row, new_tile.col + 1, new_tile.dist + 1)
      q.append(Tile)
      visited[new_tile.row][new_tile.col + 1] = True

  return -1


if __name__ == "__main__":
  lot = [
    [1, 0, 0, 0],
    [1, 0, 1, 0],
    [1, 1, 0, 0],
    [0, 1, 9, 0],
  ]
  result = min_path(4, 4, lot)
  print(result)

When I run this file, this is the output:

0
Traceback (most recent call last):
  File "code.py", line 568, in <module>
    result = min_path(4, 4, lot)
  File "code.py", line 533, in min_path
    print(new_tile.row)
AttributeError: type object 'Tile' has no attribute 'row'

Upvotes: 1

Views: 374

Answers (1)

KaeyangTheG
KaeyangTheG

Reputation: 391

Seems to be because of these lines: q.append(Tile). You are appending a reference to the class itself instead of an instance of it. Instead try something like

tile = Tile(new_tile.row - 1, new_tile.col, new_tile.dist + 1)
q.append(tile)

Upvotes: 2

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