A recursive maze solver for python. It works but has one little bug... It returns false even if it solves the maze

__init__.py

__author__ = 'Deathnerd'


maze_string_list = ("1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1",
                    "1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 1 0 1",
                    "1 1 1 0 1 0 1 1 1 1 1 1 1 0 1 1 1 0 1 0 1",
                    "1 0 0 0 1 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 1",
                    "1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1",
                    "1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1",
                    "1 1 1 0 1 1 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1",
                    "1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 1",
                    "1 0 1 0 1 1 1 0 1 1 1 0 1 0 1 1 1 0 1 1 1",
                    "1 0 1 0 0 0 1 0 0 0 1 0 1 0 1 0 1 0 1 0 1",
                    "1 0 1 1 1 1 1 0 1 1 1 0 1 0 1 0 1 1 1 0 1",
                    "1 0 1 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1",
                    "1 1 1 0 1 0 1 1 1 1 1 0 1 0 1 0 1 1 1 0 1",
                    "1 0 0 0 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 1",
                    "1 0 1 0 1 0 1 1 1 0 1 1 1 1 1 0 1 0 1 0 1",
                    "1 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 1",
                    "1 0 1 1 1 1 1 0 1 1 1 1 1 0 1 1 1 0 1 1 1",
                    "1 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 1 0 1",
                    "1 1 1 1 1 0 1 0 1 0 1 1 1 0 1 1 1 0 1 0 1",
                    "1 0 0 0 0 0 1 0 0 0 0 0 1 0 1 0 0 0 0 0 1",
                    "1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1")

maze = []
m = []
i = 0

for row in maze_string_list:
    maze.append(list(map(int, maze_string_list[i].split(" "))))
    i += 1

solver.py

__author__ = 'Deathnerd'

"""
It works.... somewhat. Returns false even though it solves it
"""

from maze import maze
import msvcrt as m  # Only works in windows


def wait():
    m.getch()


def print_maze():
    for x in maze:
        print x
    print "\n"


def solve():
    return _solver(maze[0].index(0), 0)


def _solver(x_position, y_position):
    print_maze()
    wait()  # Uncomment this to wait for user input on each iteration
    maze[y_position][x_position] = 2  # mark as visited
    if y_position == maze.__len__() - 1:
        return True

    # move down
    down_position = maze[y_position + 1][x_position]
    if down_position is not 1 and down_position is not 2:
        _solver(x_position, y_position + 1)

    # move up
    up_position = maze[y_position - 1][x_position]
    if y_position is not 0 and up_position is not 1 and up_position is not 2:
        _solver(x_position, y_position - 1)

    # move left
    left_position = maze[y_position][x_position - 1]
    if x_position is not 0 and left_position is not 1 and left_position is not 2:
        _solver(x_position - 1, y_position)

    # move right
    right_position = maze[y_position][x_position + 1]
    if x_position is not maze[0].__len__() - 1 and right_position is not 1 and right_position is not 2:
        _solver(x_position + 1, y_position)

    # everything failed. Mark it as a failure
    maze[y_position][x_position] = 0
    return False