"""This module contains code from Think Python by Allen B. Downey http://thinkpython.com Copyright 2012 Allen B. Downey License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html """ import math from Wobbler import * class Missed(Exception): """Exception raised when a turtle tries to tag someone too far away.""" class Tagger(Wobbler): """Represents a Turtle that plays tag.""" def __init__(self, world, speed=1, clumsiness=60, color='red'): # call the __init__ method from Wobbler to initialize # world, speed, clumsiness, and color. Wobbler.__init__(self, world, speed, clumsiness, color) # then initialize the additional attributes that Taggers have self.it = 0 self.sulking = 0 def steer(self): """Steers the Wobbler in the general direction it should go. Postcondition: the Wobbler's heading may be changed, but its position may not. """ # if sulking, decrement the sulking clock if self.sulking > 0: self.sulking -= 1 if self.sulking == 0: self.color = 'red' self.speed = self.old_speed return # if out of bounds, turn toward the center if self.distance() > 200: self.turn_toward(0, 0) return # if not it, just wander if not self.it: return # if it, chase the closest player target = self.closest(self.world.animals) try: self.apply_tag(target) except Missed: self.chase(target) def turn_toward(self, x=0, y=0): """Turns to face the given point. x, y: point to turn toward """ self.heading = self.away(x, y) + 180 self.redraw() def away(self, x=0, y=0): """Computes the heading away from the given point. x, y: point to face away from """ dx = self.x - x dy = self.y - y heading = math.atan2(dy, dx) return heading * 180 / math.pi def distance(self, x=0, y=0): """Computes the distance from this turtle to the given point. x, y: point to find distance to """ dx = self.x - x dy = self.y - y return math.sqrt(dx**2 + dy**2) def distance_from(self, other): """Computes the distance between turtles. other: Turtle object """ return self.distance(other.x, other.y) def youre_it(self): """Makes this turtle it.""" self.it = 1 self.old_speed = self.speed self.old_color = self.color self.speed = 0 self.color = 'blue' self.sulking = 200 self.redraw() def not_it(self): """Makes this turtle not it.""" self.it = 0 self.color = self.old_color self.redraw() def flee(self, other): """Faces away from the other turtle. other: Turtle object """ self.heading = self.away(other.x, other.y) def chase(self, other): """Faces the other turtle. other: Turtle object """ self.turn_toward(other.x, other.y) def closest(self, others): """Return closest animal in the list (other than self). others: list of Animals """ t = [(self.distance_from(animal), animal) for animal in others if animal is not self] (distance, animal) = min(t) return animal def apply_tag(self, other): """Tried to tag the other turtle. If it is too far away, raises an exception. other: Turtle object """ if self.distance_from(other) < 10: self.not_it() other.youre_it() else: raise Missed if __name__ == '__main__': world = make_world(Tagger) world.animals[0].youre_it() world.mainloop()