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# Snake_ladder game using doubly linked list

class Empty(Exception):
    """ Error attempting to access an element from an empty container."""
    pass


class DoublyLinkedBase:
    """Queue implementation using circularly linked list for storage."""

    # -------------------------- nested Node class --------------------------
    class _Node:
        """ Lightweight, nonpublic class for storing a doubly linked node. """
        __slots__ = '_element', '_prev', '_next'  # streamline memory usage

        def __init__(self, element, prev, next):  # initialize node’s fields
            self._element = element  # reference to user’s element
            self._prev = prev  # previous node reference
            self._next = next  # next node reference

    # ------------------------------- methods -------------------------------

    def __init__(self):
        """ Create an empty list."""
        self._header = self._Node(None, None, None)
        self._trailer = self._Node(None, None, None)
        self._header._next = self._trailer  # trailer is after header
        self._trailer._prev = self._header  # header is before trailer
        self._size = 0  # number of elements

    def __len__(self):
        """Return the number of elements in the list."""
        return self._size

    def is_empty(self):
        """Return True if list is empty."""
        return self._size == 0

    def insert_between(self, e, predecessor, successor):
        """Add element e between two existing nodes and return new node."""
        newest = self._Node(e, predecessor, successor)  # linked to neighbors
        predecessor._next = newest
        successor._prev = newest
        self._size += 1
        return newest

    def delete_node(self, node):
        """ Delete nonsentinel node from the list and return its element."""
        predecessor = node._prev
        successor = node._next
        predecessor._next = successor
        successor._prev = predecessor
        self._size -= 1
        element = node._element  # record deleted element
        node._prev = node._next = node._element = None  # deprecate node
        return element  # return deleted element

    def display_board(self):
        current = self._header._next
        while current != self._trailer:
            print(current._element, end=" ")
            current = current._next
        print()

    def dice_roll_sequance(self, case):  # not a random sequance
        if case == 1:
            self._dice_seq = [1, 5, 3]  # 84
            self.move_()
            print("case %d, ans = 84" % case)
        if case == 2:
            self._dice_seq = [4, 3, 6, 1]  # 38
            self.move_()
            print("case %d, ans = 38" % case)
        if case == 3:
            self._dice_seq = [5, 2, 6, 6, 3, 6, 5, 5]  # 100 win
            self.move_()
            print("case %d, ans = 100 win" % case)
        if case == 4:
            self._dice_seq = [5, 2, 6, 6, 3, 6, 5, 1]  # 61
            self.move_()
            print("case %d, ans = 61 " % case)
        if case == 5:
            self._dice_seq = [5, 2, 6, 6, 3, 6, 5, 6]  # 95
            self.move_()
            print("case %d, ans = 95" % case)
        if case == 6:
            self._dice_seq = [1]  # 38
            self.move_()
            print("case %d, ans = 38" % case)
        if case == 7:
            self._dice_seq = [6, 1, 2]  # 5
            self.move_()
            print("case %d, ans = 5" % case)
        if case == 8:
            self._dice_seq = [6, 1, 2, 3]  # 31
            self.move_()
            print("case %d, ans = 31" % case)
        if case == 9:
            self._dice_seq = [1, 6, 6, 1, 6, 2]  # 99
            self.move_()
            print("case %d, ans =99" % case)

    def inistialize_board(self):
        for i in range(1, 101):

            if i == 2:
                self.insert_last(i, 36)
            elif i == 8:
                self.insert_last(i, 23)
            elif i == 17:
                self.insert_last(i, 6)
            elif i == 21:
                self.insert_last(i, 21)
            elif i == 33:
                self.insert_last(i, -28)
            elif i == 46:
                self.insert_last(i, 38)
            elif i == 51:
                self.insert_last(i, 16)
            elif i == 54:
                self.insert_last(i, -20)
            elif i == 63:
                self.insert_last(i, -47)
            elif i == 69:
                self.insert_last(i, i + 2)
            elif i == 71:
                self.insert_last(i, 20)
            elif i == 75:
                self.insert_last(i, 5)
            elif i == 80:
                self.insert_last(i, 19)
            elif i == 93:
                self.insert_last(i, -19)
            elif i == 96:
                self.insert_last(i, 1)
            elif i == 97:
                self.insert_last(i, -36)
            else:
                self.insert_last(i, 0)

    def move_(self):
      current = self._header or self._trailer
      if current is not None:
          for roll in self._dice_seq:
              for _ in range(roll):
                  if current._next is not None and current._next._element is not None and current._next != self._trailer:
                      current = current._next
                      print("Moved to square", current._element)
                  else:
                      break
          if current is not None and current != self._trailer:
              self._header = current
              print("Current position:", current._element)
          else:
              print("Current position: None")
      else:
          print("Current position: None")


    def check_win(self):
        return self._header._element == 100

    # Add this method inside the DoublyLinkedBase class

    def insert_last(self, square_id, move_shift):
        current = self._header._next
        while current:
            if current._element == square_id:
                current._element += move_shift
                # Ensure the circular behavior
                if current._element > 100:
                    current._element = 200 - current._element
                print("Moved to square", current._element)
                self._header = current  
                return
            current = current._next

     
# Main dirver

dl = DoublyLinkedBase()

dl.inistialize_board()

dl.display_board()

for i in range(1, 10):
    dl.dice_roll_sequance(i)


What I have tried:

What modification do I make so that it does not print none ?(the code linked list)
the output :
Current position: None
case 1, ans = 84
Current position: None
case 2, ans = 38
Current position: None
case 3, ans = 100 win
Current position: None
case 4, ans = 61 
Current position: None
case 5, ans = 95
Current position: None
case 6, ans = 38
Current position: None
case 7, ans = 5
Current position: None
case 8, ans = 31
Current position: None
case 9, ans =99
Posted
Updated 26-Dec-23 5:43am
v2

1 solution

Firstly, start by finding out where it's printing "Current position: None" - there are two places that explicitly print that, and one that could print that if the valuer of current._element was None. You can use the debugger to step through your code and find that out: pdb — The Python Debugger — Python 3.12.1 documentation[^] will help if you don't know how to use it.

Then look at why it got to that position, what path if followed and why. What caused it to go that way? What variables didn't have the expected values? What were they set to; what should they contain? Where should they have been set? Why weren't they?

When you know all that, it should be fairly clear to the author that code (i.e. you) what the problem is and you should be able to fix it.

But getting your code to run properly is a big part of an assignment, and you won't learn how to fix complicated code until you can fix simple code like this!
 
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