# [Tutor] robots question

Roelof Wobben rwobben at hotmail.com
Thu Sep 16 17:16:11 CEST 2010

```Hello,

As a exercise from this book ( Thinking like a computer scientist ) I have to make this programm on this page(http://openbookproject.net/thinkcs/python/english2e/ch12.html)
Exercise 11

#
# robots.py
#
from gasp import *

SCREEN_WIDTH = 640
SCREEN_HEIGHT = 480
GRID_WIDTH = SCREEN_WIDTH/10 - 1
GRID_HEIGHT = SCREEN_HEIGHT/10 - 1

def place_player():
# x = random.randint(0, GRID_WIDTH)
# y = random.randint(0, GRID_HEIGHT)
x, y = GRID_WIDTH/2 + 3, GRID_HEIGHT/2
return {'shape': Circle((10*x+5, 10*y+5), 5, filled=True), 'x': x, 'y': y}

def place_robot(x,y, junk):
x = random.randint(0, GRID_WIDTH)
y = random.randint(0, GRID_HEIGHT)
return {'shape': Box((10*x, 10*y), 10, 10), 'x': x, 'y': y}

def place_robots(numbots):
robots = []
# for i in range(numbots):
#    x = random.randint(0, GRID_WIDTH)
#    y = random.randint(0, GRID_HEIGHT)
#    robots.append(place_robot(x, y))
robots.append(place_robot(GRID_WIDTH/2 - 4, GRID_HEIGHT/2 + 2, junk= False))
robots.append(place_robot(GRID_WIDTH/2 - 4, GRID_HEIGHT/2 - 2, junk = False))
return robots

def move_player(player):
update_when('key_pressed')
if key_pressed('escape'):
return True
elif key_pressed('4'):
if player['x'] > 0: player['x'] -= 1
elif key_pressed('7'):
if player['x'] > 0: player['x'] -= 1
if player['y'] < GRID_HEIGHT: player['y'] += 1
elif key_pressed('8'):
if player['y'] < GRID_HEIGHT: player['y'] += 1
elif key_pressed('9'):
if player['x'] < GRID_WIDTH: player['x'] += 1
if player['y'] < GRID_HEIGHT: player['y'] += 1
elif key_pressed('6'):
if player['x'] < GRID_WIDTH: player['x'] += 1
elif key_pressed('3'):
if player['x'] < GRID_WIDTH: player['x'] += 1
if player['y'] > 0: player['y'] -= 1
elif key_pressed('2'):
if player['y'] > 0: player['y'] -= 1
elif key_pressed('1'):
if player['x'] > 0: player['x'] -= 1
if player['y'] > 0: player['y'] -= 1
elif key_pressed('0'):
player['x'] = random.randint(0, GRID_WIDTH)
player['y'] = random.randint(0, GRID_HEIGHT)
else:
return False

move_to(player['shape'], (10*player['x']+5, 10*player['y']+5))

return False

def collided(thing1, thing2):
return thing1['x'] == thing2['x'] and thing1['y'] == thing2['y']

def check_collisions(robots, junk, player):
# check whether player has collided with anything
for thing in robots + junk:
if collided(thing, player):
return True
return False

def move_robot(robot, player):
if robot['x'] < player['x']: robot['x'] += 1
elif robot['x'] > player['x']: robot['x'] -= 1

if robot['y'] < player['y']: robot['y'] += 1
elif robot['y'] > player['y']: robot['y'] -= 1

move_to(robot['shape'], (10*robot['x'], 10*robot['y']))

def move_robots(robots, player):
for robot in robots:
move_robot(robot, player)

def play_game(robots):
begin_graphics(SCREEN_WIDTH, SCREEN_HEIGHT)
player = place_player()
robot = place_robots(4)
junk = [place_robot(GRID_WIDTH/2, GRID_HEIGHT/2, junk="true" )]
defeated = False

while not defeated:
quit =  move_player(player)
if quit:
break
move_robots(robot, player)
defeated = check_collisions(robot, player, junk)

if defeated:
remove_from_screen(player['shape'])
for thing in robots + junk:
remove_from_screen(thing['shape'])
Text("They got you!", (240, 240), size=32)
sleep(3)

end_graphics()

if __name__ == '__main__':
play_game(2)

But now Im getting this error message :

Traceback (most recent call last):
File "/root/workspace/test2/src/test.py", line 120, in <module>
play_game(2)
File "/root/workspace/test2/src/test.py", line 106, in play_game
defeated = check_collisions(robot, player, junk)
File "/root/workspace/test2/src/test.py", line 73, in check_collisions
for thing in robots + junk:
TypeError: can only concatenate list (not "dict") to list

I understand that robots is a dict and junk is a list.

Is that right ?

And why does the book say that when this message is appearing.

Roelof

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```