Mariam Haji wrote:
> Hi guys,
>
> I am still on the learn python the hard way.
> I built the below on python 2.7 and my OS is windows 7.
>
> I am getting this error:
> Traceback (most recent call last):
> File "ex43.py", line 205, in <module>
> a_game.play()
> File "ex43.py", line 21, in play
> next_scene_name = current_scene.enter()
> AttributeError: 'NoneType' object has no attribute 'enter'
The value of current_scene is None here. If you dig a bit in your code
looking for places where that can happen you end up with
> class Map(object):
> scenes = {
> 'central_corridor': CentralCorridor(),
> 'laser_weapon_armory': LaserWeaponArmory(),
> 'the_bridge': TheBridge(),
> 'escape_pod': EscapePod(),
> 'death': Death()
> }
>
> def __init__(self, start_scene):
> self.start_scene = start_scene
>
> def next_scene(self, scene_name):
> return Map.scenes.get(scene_name)
Map.scenes is a dict, and its get() method returns None when the lookup for
a key fails. If you pass an unknown scene name to the next_scene() method it
returns None rather than a Scene instance.
As a first step to fix this I recommend that you use the item lookup
operator instead of the method:
def next_scene(self, scene_name):
return Map.scenes[scene_name]
This will fail immediately, and the error message should be more
informative. I got:
Traceback (most recent call last):
File "./game_mariam.py", line 181, in <module>
a_game.play()
File "./game_mariam.py", line 20, in play
current_scene = self.scene_map.next_scene(next_scene_name)
File "./game_mariam.py", line 173, in next_scene
return Map.scenes[scene_name]
KeyError: 'laser_weapon_armoury'
That is, you need to decide if you want British or American orthography.
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