Environment kuimaze2.SearchProblem shall be used for problems of finding the shortest path in a maze. It is used in optional task 01-easy_search and the first mandatory semestral task 03-search.

Available methods

After creation of the SearchProblem instance (see Usage), you can use the following methods of the environment:

  • env.get_start() returns the start State of the problem.
  • env.get_goals() returns the set of goal States of the problem.
  • env.is_goal(state) returns True, if the state is among the goal states.
  • env.get_actions(state) returns a list of all actions available in the given state.
  • env.get_transition_result(state, action) returns a pair of (new_state, transition_cost) when choosing applying action in state.
  • env.render() updates the graphical display of the environment. For the explanation of various parameters of this method, see help(env.render).


To use the environment, you need to:

  • Import it:
    >>> from kuimaze2 import SearchProblem, Map
  • Create an instance of the environment with the chosen map:
    >>> MAP = "S...G"
    >>> env = SearchProblem(Map.from_string(MAP))
  • Get the start (and goals, if needed):
    >>> start = env.get_start() # start State
    >>> start
    State(r=0, c=0)
    >>> goals = env.get_goals() # set of goal States
    >>> goals
    {State(r=0, c=4)}
  • Communicate with the environment:
    >>> actions = env.get_actions(start)
    >>> actions
    [<Action.UP: 0>, <Action.RIGHT: 1>, <Action.DOWN: 2>, <Action.LEFT: 3>]
    >>> next_state, cost = env.get_transition_result(start, actions[0])
    >>> next_state
    State(r=0, c=0)   # It is not possible to go UP from the start state, so stay in place
    >>> cost
    1                 # Although you stayed in place, the action costs you 1 unit
    >>> env.get_transition_result(start, actions[1])  # ... but it should be possible to go RIGHT
    (State(r=0, c=1), 1)                              # And yes, it is, we moved.

To update the graphical display of the environment (if you created it with env = SearchProblem(…, graphics=True)), use:

Method render() has many arguments that can be used to display various parts of your algorithm. See help(SearchProblem.render).

courses/be5b33kui/semtasks/kuimaze/10_searchproblem.txt · Last modified: 2024/02/20 16:09 by xposik