How can I fix the Type Error: 'int' object is not subscriptable for 8-piece puzzle?

Question

I am implementing a best first search and A* algorithms to solve the 8-piece puzzle program, but first need to verify if a state is solvable or not.

To find if a state is solvable or not I use the number of inversions and the parity of that number. Look here more information on finding solvable states.

My question resides inside the solvable function:

 20     def solvable(self):
 21         total=0
 22         for i in range(8):
 23             step = i+1
 24             row = i//3
 25             col = i%3
 26             print("row: ",row," col: ",col)
 27             value = int(self.state[row][col])
 28             for j in range(step,9):
 29                 row2 = i//3
 30                 col2 = i%3
 31                 value2 = self.state[row2][column2]
 32                 if not value2==0 and value2>value:
 33                     total+=1
 34         return total

Right now, it just returns the total so I can check that it is computing the right value before I return a basic true or false.

The simple script I use to create a state and call solvable on that state is:

  1 import tempStateController as sc
  2 obj = sc.State([5,4,3],[2,1,7],[8,0,6])
  3 obj.solvable()

The error that I am running into looks like:

Traceback (most recent call last):
  File "test.py", line 3, in <module>
    obj.solvable()
  File "/home/colin/Documents/gradSchool/spring2019/ai/hw/bestFirstAStar/tempStateController.py", line 27, in solvable
    value = int(self.state[row][col])
TypeError: 'int' object is not subscriptable

Here is my complete stateController code:

  1 #this is a generic state class that holds the values of each
  2 #position in the environment class State:
  3 class State:
  4     parent=None
  5     children=[]
  6     cost=0
  7     ID=0
  8     
  9     state = [[0,0,0],[0,0,0],[0,0,0]]
 10 
 11     def __init__(self,state,parent=None,children=None):
 12         self.state = state
 13         self.parent = parent
 14         if children:
 15             self.children = children
 16             
 17     #check a state is solvable 
 18     def solvable(self):
 19         total=0
 20         for i in range(8):
 21             step = i+1
 22             row = i//3
 23             col = i%3
 24             print("row: ",row," col: ",col)
 25             value = int(self.state[row][col])
 26             for j in range(step,9):
 27                 row2 = i//3
 28                 col2 = i%3
 29                 value2 = self.state[row2][column2]
 30                 if not value2==0 and value2>value:
 31                     total+=1
 32         return total

Here is a quick walk through of how to find the number of inversions for a state:

inversions walk through

Any help is greatly appreciated! Thanks.

Answer 1

You have a typo. You've passed three lists:

obj = sc.State([5,4,3],[2,1,7],[8,0,6])

instead of a list of lists:

obj = sc.State([[5,4,3],[2,1,7],[8,0,6]])

state equals [5,4,3], so self.state[row2] equals 5. Effectively making 5[column2] return int not subscriptable.